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<a name="EN-US_TOPIC_0000002043982200"></a><a name="EN-US_TOPIC_0000002043982200"></a>
<h1 class="topictitle1">Common JDBC Development Examples</h1>
<div id="body8662426"><div class="section" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_section8820452474"><h4 class="sectiontitle">Example 1</h4><p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p6320181125511">Before completing the following example, you need to create a stored procedure.</p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_s9dfd0fc5586d464ebdf741ac5a35b8fc"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
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<span class="p">(</span>
<span class="w"> </span><span class="n">psv_in1</span><span class="w"> </span><span class="k">in</span><span class="w"> </span><span class="nb">integer</span><span class="p">,</span>
<span class="w"> </span><span class="n">psv_in2</span><span class="w"> </span><span class="k">in</span><span class="w"> </span><span class="nb">integer</span><span class="p">,</span>
<span class="w"> </span><span class="n">psv_inout</span><span class="w"> </span><span class="k">in</span><span class="w"> </span><span class="k">out</span><span class="w"> </span><span class="nb">integer</span>
<span class="p">)</span>
<span class="k">as</span>
<span class="k">begin</span>
<span class="w"> </span><span class="n">psv_inout</span><span class="w"> </span><span class="p">:</span><span class="o">=</span><span class="w"> </span><span class="n">psv_in1</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">psv_in2</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">psv_inout</span><span class="p">;</span>
<span class="k">end</span><span class="p">;</span>
<span class="o">/</span>
</pre></div></td></tr></table></div>
</div>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_a576944990d75455893aebb8e8f175b6f">This example illustrates how to develop applications based on the <span id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_text1800809317">GaussDB(DWS)</span> JDBC interface.</p>
<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_s745314d7b40b42dd99a0c2b182cf2b67"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
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<span class="c1">//gsjdbc4.jar is used as an example.</span>
<span class="c1">// This example illustrates the main processes of JDBC-based development, covering database connection creation, table creation, and data insertion.</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.Connection</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.DriverManager</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.PreparedStatement</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.SQLException</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.Statement</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.CallableStatement</span><span class="p">;</span>
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">DBTest</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Establish a connection to the database.</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Connection</span><span class="w"> </span><span class="nf">GetConnection</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">passwd</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">driver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;org.postgresql.Driver&quot;</span><span class="p">;</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">sourceURL</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;jdbc:postgresql://localhost:/gaussdb&quot;</span><span class="p">;</span>
<span class="w"> </span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Load the database driver.</span>
<span class="w"> </span><span class="n">Class</span><span class="p">.</span><span class="na">forName</span><span class="p">(</span><span class="n">driver</span><span class="p">).</span><span class="na">newInstance</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Establish a connection to the database.</span>
<span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DriverManager</span><span class="p">.</span><span class="na">getConnection</span><span class="p">(</span><span class="n">sourceURL</span><span class="p">,</span><span class="w"> </span><span class="n">username</span><span class="p">,</span><span class="w"> </span><span class="n">passwd</span><span class="p">);</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;Connection succeed!&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">conn</span><span class="p">;</span>
<span class="w"> </span><span class="p">};</span>
<span class="w"> </span><span class="c1">//Run an ordinary SQL statement. Create a customer_t1 table.</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">CreateTable</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">Statement</span><span class="w"> </span><span class="n">stmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">stmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conn</span><span class="p">.</span><span class="na">createStatement</span><span class="p">();</span>
<span class="w"> </span><span class="c1">//Run an ordinary SQL statement.</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stmt</span>
<span class="w"> </span><span class="p">.</span><span class="na">executeUpdate</span><span class="p">(</span><span class="s">&quot;CREATE TABLE customer_t1(c_customer_sk INTEGER, c_customer_name VARCHAR(32));&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="n">stmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">stmt</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">stmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e1</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">//Run the preprocessing statement to insert data in batches.</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">BatchInsertData</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">PreparedStatement</span><span class="w"> </span><span class="n">pst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Generate a prepared statement.</span>
<span class="w"> </span><span class="n">pst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conn</span><span class="p">.</span><span class="na">prepareStatement</span><span class="p">(</span><span class="s">&quot;INSERT INTO customer_t1 VALUES (?,?)&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Add parameters.</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">setInt</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">setString</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;data &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="p">);</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">addBatch</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">//Run batch processing.</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">executeBatch</span><span class="p">();</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pst</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e1</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">//Run the precompilation statement to update data.</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">ExecPreparedSQL</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">PreparedStatement</span><span class="w"> </span><span class="n">pstmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">pstmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conn</span>
<span class="w"> </span><span class="p">.</span><span class="na">prepareStatement</span><span class="p">(</span><span class="s">&quot;UPDATE customer_t1 SET c_customer_name = ? WHERE c_customer_sk = 1&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="n">pstmt</span><span class="p">.</span><span class="na">setString</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;new Data&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rowcount</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pstmt</span><span class="p">.</span><span class="na">executeUpdate</span><span class="p">();</span>
<span class="w"> </span><span class="n">pstmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pstmt</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">pstmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e1</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="c1">//Run a stored procedure.</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">ExecCallableSQL</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">CallableStatement</span><span class="w"> </span><span class="n">cstmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span>
<span class="w"> </span><span class="n">cstmt</span><span class="o">=</span><span class="n">conn</span><span class="p">.</span><span class="na">prepareCall</span><span class="p">(</span><span class="s">&quot;{? = CALL TESTPROC(?,?,?)}&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="n">cstmt</span><span class="p">.</span><span class="na">setInt</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">50</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="n">cstmt</span><span class="p">.</span><span class="na">setInt</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">20</span><span class="p">);</span>
<span class="w"> </span><span class="n">cstmt</span><span class="p">.</span><span class="na">setInt</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">90</span><span class="p">);</span>
<span class="w"> </span><span class="n">cstmt</span><span class="p">.</span><span class="na">registerOutParameter</span><span class="p">(</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">Types</span><span class="p">.</span><span class="na">INTEGER</span><span class="p">);</span><span class="w"> </span><span class="c1">//Register an OUT parameter as an integer.</span>
<span class="w"> </span><span class="n">cstmt</span><span class="p">.</span><span class="na">execute</span><span class="p">();</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">out</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">cstmt</span><span class="p">.</span><span class="na">getInt</span><span class="p">(</span><span class="mi">4</span><span class="p">);</span><span class="w"> </span><span class="c1">//Obtain the out parameter value.</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;The CallableStatment TESTPROC returns:&quot;</span><span class="o">+</span><span class="n">out</span><span class="p">);</span>
<span class="w"> </span><span class="n">cstmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">cstmt</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">cstmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e1</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span>
<span class="w"> </span><span class="cm">/**</span>
<span class="cm"> * Main process. Call static methods one by one.</span>
<span class="cm"> * @param args</span>
<span class="cm"> */</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Establish a connection to the database.</span>
<span class="w"> </span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">GetConnection</span><span class="p">(</span><span class="s">&quot;tester&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;password&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Create a table.</span>
<span class="w"> </span><span class="n">CreateTable</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Insert data in batches.</span>
<span class="w"> </span><span class="n">BatchInsertData</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Run the precompilation statement to update data.</span>
<span class="w"> </span><span class="n">ExecPreparedSQL</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Run a stored procedure.</span>
<span class="w"> </span><span class="n">ExecCallableSQL</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Close the connection to the database.</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">conn</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="section" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_section112115111092"><h4 class="sectiontitle">Example 2: High Client Memory Usage</h4><p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p13961185014617">In this example, <strong id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_b842352706155628">setFetchSize</strong> adjusts the memory usage of the client by using the database cursor to obtain server data in batches. It may increase network interaction and damage some performance.</p>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p28831955345">The cursor is valid within a transaction. Therefore, you need to disable the autocommit function.</p>
<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_screen14336113936"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
<span class="normal"> 3</span>
<span class="normal"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
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<span class="normal">20</span>
<span class="normal">21</span>
<span class="normal">22</span></pre></div></td><td class="code"><div><pre><span></span><span class="c1">// Disable the autocommit function.</span>
<span class="n">conn</span><span class="p">.</span><span class="na">setAutoCommit</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span>
<span class="n">Statement</span><span class="w"> </span><span class="n">st</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conn</span><span class="p">.</span><span class="na">createStatement</span><span class="p">();</span>
<span class="c1">// Open the cursor and obtain 50 lines of data each time.</span>
<span class="n">st</span><span class="p">.</span><span class="na">setFetchSize</span><span class="p">(</span><span class="mi">50</span><span class="p">);</span>
<span class="n">ResultSet</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">st</span><span class="p">.</span><span class="na">executeQuery</span><span class="p">(</span><span class="s">&quot;SELECT * FROM mytable&quot;</span><span class="p">);</span>
<span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">rs</span><span class="p">.</span><span class="na">next</span><span class="p">()){</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&quot;a row was returned.&quot;</span><span class="p">);</span>
<span class="p">}</span>
<span class="n">rs</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="c1">// Disable the server cursor.</span>
<span class="n">st</span><span class="p">.</span><span class="na">setFetchSize</span><span class="p">(</span><span class="mi">0</span><span class="p">);</span>
<span class="n">rs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">st</span><span class="p">.</span><span class="na">executeQuery</span><span class="p">(</span><span class="s">&quot;SELECT * FROM mytable&quot;</span><span class="p">);</span>
<span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">rs</span><span class="p">.</span><span class="na">next</span><span class="p">()){</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">print</span><span class="p">(</span><span class="s">&quot;many rows were returned.&quot;</span><span class="p">);</span>
<span class="p">}</span>
<span class="n">rs</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="c1">// Close the statement.</span>
<span class="n">st</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
</pre></div></td></tr></table></div>
</div>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p1969114711314"></p>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p8227164783113"></p>
</div>
<div class="section" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_section199071952123210"><h4 class="sectiontitle">Retrying SQL Queries for Applications</h4><p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_a51af6c623abc43deb9a68807ad0856d2">If the primary DN is faulty and cannot be restored within 40 seconds, its standby is automatically promoted to primary to ensure that the cluster runs properly. Jobs running during the switchover will fail and those started after the switchover will not be affected. To protect upper-layer services from being affected by the failover, refer to the following example to construct a SQL retry mechanism at the service layer.</p>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p14281191763"></p>
<div class="p" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p228113917616"><strong id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_b382163312166">gsjdbc4.jar</strong> is used as an example.<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_screen145400210509"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
<span class="normal"> 3</span>
<span class="normal"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span>
<span class="normal">13</span>
<span class="normal">14</span>
<span class="normal">15</span>
<span class="normal">16</span>
<span class="normal">17</span>
<span class="normal">18</span>
<span class="normal">19</span>
<span class="normal">20</span>
<span class="normal">21</span>
<span class="normal">22</span>
<span class="normal">23</span>
<span class="normal">24</span>
<span class="normal">25</span>
<span class="normal">26</span>
<span class="normal">27</span>
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<span class="normal">40</span>
<span class="normal">41</span>
<span class="normal">42</span>
<span class="normal">43</span>
<span class="normal">44</span>
<span class="normal">45</span>
<span class="normal">46</span>
<span class="normal">47</span>
<span class="normal">48</span>
<span class="normal">49</span>
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<span class="normal">53</span>
<span class="normal">54</span>
<span class="normal">55</span></pre></div></td><td class="code"><div><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.Connection</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.DriverManager</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.PreparedStatement</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.ResultSet</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.SQLException</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.Statement</span><span class="p">;</span>
<span class="cm">/**</span>
<span class="cm"> * </span>
<span class="cm"> *</span>
<span class="cm"> */</span>
<span class="kd">class</span> <span class="nc">ExitHandler</span><span class="w"> </span><span class="kd">extends</span><span class="w"> </span><span class="n">Thread</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="n">Statement</span><span class="w"> </span><span class="n">cancel_stmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">ExitHandler</span><span class="p">(</span><span class="n">Statement</span><span class="w"> </span><span class="n">stmt</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kd">super</span><span class="p">(</span><span class="s">&quot;Exit Handler&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">cancel_stmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stmt</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">run</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;exit handle&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">cancel_stmt</span><span class="p">.</span><span class="na">cancel</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;cancel query failed.&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">SQLRetry</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Establish a connection to the database.</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="n">Connection</span><span class="w"> </span><span class="nf">GetConnection</span><span class="p">(</span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">passwd</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">driver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;org.postgresql.Driver&quot;</span><span class="p">;</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">sourceURL</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;jdbc:postgresql://10.131.72.136:8000/gaussdb&quot;</span><span class="p">;</span>
<span class="w"> </span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Load the database driver.</span>
<span class="w"> </span><span class="n">Class</span><span class="p">.</span><span class="na">forName</span><span class="p">(</span><span class="n">driver</span><span class="p">).</span><span class="na">newInstance</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Establish a connection to the database.</span>
<span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DriverManager</span><span class="p">.</span><span class="na">getConnection</span><span class="p">(</span><span class="n">sourceURL</span><span class="p">,</span><span class="w"> </span><span class="n">username</span><span class="p">,</span><span class="w"> </span><span class="n">passwd</span><span class="p">);</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;Connection succeed!&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">conn</span><span class="p">;</span>
<span class="p">}</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="p" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p11900645501">Run an ordinary SQL statement. Create the <strong id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_b102511219202017">jdbc_test1</strong> table.<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_screen13112461014"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
<span class="normal"> 3</span>
<span class="normal"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span>
<span class="normal">13</span>
<span class="normal">14</span>
<span class="normal">15</span>
<span class="normal">16</span>
<span class="normal">17</span>
<span class="normal">18</span>
<span class="normal">19</span>
<span class="normal">20</span>
<span class="normal">21</span>
<span class="normal">22</span>
<span class="normal">23</span>
<span class="normal">24</span>
<span class="normal">25</span>
<span class="normal">26</span>
<span class="normal">27</span></pre></div></td><td class="code"><div><pre><span></span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">CreateTable</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">Statement</span><span class="w"> </span><span class="n">stmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">stmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conn</span><span class="p">.</span><span class="na">createStatement</span><span class="p">();</span>
<span class="w"> </span><span class="c1">// add ctrl+c handler</span>
<span class="w"> </span><span class="n">Runtime</span><span class="p">.</span><span class="na">getRuntime</span><span class="p">().</span><span class="na">addShutdownHook</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ExitHandler</span><span class="p">(</span><span class="n">stmt</span><span class="p">));</span>
<span class="w"> </span><span class="c1">//Run an ordinary SQL statement.</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rc2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stmt</span>
<span class="w"> </span><span class="p">.</span><span class="na">executeUpdate</span><span class="p">(</span><span class="s">&quot;DROP TABLE if exists jdbc_test1;&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">rc1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">stmt</span>
<span class="w"> </span><span class="p">.</span><span class="na">executeUpdate</span><span class="p">(</span><span class="s">&quot;CREATE TABLE jdbc_test1(col1 INTEGER, col2 VARCHAR(10));&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="n">stmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">stmt</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">stmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e1</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
</pre></div></td></tr></table></div>
</div>
</div>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p18159114716593">Run the preprocessing statement to insert data in batches.</p>
<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_screen155081256014"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
<span class="normal"> 3</span>
<span class="normal"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span>
<span class="normal">13</span>
<span class="normal">14</span>
<span class="normal">15</span>
<span class="normal">16</span>
<span class="normal">17</span>
<span class="normal">18</span>
<span class="normal">19</span>
<span class="normal">20</span>
<span class="normal">21</span>
<span class="normal">22</span>
<span class="normal">23</span>
<span class="normal">24</span>
<span class="normal">25</span>
<span class="normal">26</span>
<span class="normal">27</span></pre></div></td><td class="code"><div><pre><span></span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">BatchInsertData</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">PreparedStatement</span><span class="w"> </span><span class="n">pst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Generate a prepared statement.</span>
<span class="w"> </span><span class="n">pst</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conn</span><span class="p">.</span><span class="na">prepareStatement</span><span class="p">(</span><span class="s">&quot;INSERT INTO jdbc_test1 VALUES (?,?)&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="mi">100</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Add parameters.</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">setInt</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">setString</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;data &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="p">);</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">addBatch</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">//Run batch processing.</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">executeBatch</span><span class="p">();</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pst</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">pst</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e1</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span>
</pre></div></td></tr></table></div>
</div>
<div class="p" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p9931185811587">Run the precompilation statement to update data.<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_screen1885151875911"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
<span class="normal"> 3</span>
<span class="normal"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span>
<span class="normal">13</span>
<span class="normal">14</span>
<span class="normal">15</span>
<span class="normal">16</span>
<span class="normal">17</span>
<span class="normal">18</span>
<span class="normal">19</span>
<span class="normal">20</span>
<span class="normal">21</span>
<span class="normal">22</span>
<span class="normal">23</span>
<span class="normal">24</span>
<span class="normal">25</span>
<span class="normal">26</span>
<span class="normal">27</span>
<span class="normal">28</span>
<span class="normal">29</span>
<span class="normal">30</span>
<span class="normal">31</span>
<span class="normal">32</span>
<span class="normal">33</span></pre></div></td><td class="code"><div><pre><span></span><span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="nf">QueryRedo</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="p">){</span>
<span class="w"> </span><span class="n">PreparedStatement</span><span class="w"> </span><span class="n">pstmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">retValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">pstmt</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conn</span>
<span class="w"> </span><span class="p">.</span><span class="na">prepareStatement</span><span class="p">(</span><span class="s">&quot;SELECT col1 FROM jdbc_test1 WHERE col2 = ?&quot;</span><span class="p">);</span>
<span class="w"> </span>
<span class="w"> </span><span class="n">pstmt</span><span class="p">.</span><span class="na">setString</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;data 10&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="n">ResultSet</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">pstmt</span><span class="p">.</span><span class="na">executeQuery</span><span class="p">();</span>
<span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">rs</span><span class="p">.</span><span class="na">next</span><span class="p">())</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;col1 = &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">rs</span><span class="p">.</span><span class="na">getString</span><span class="p">(</span><span class="s">&quot;col1&quot;</span><span class="p">));</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">rs</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span>
<span class="w"> </span><span class="n">pstmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="n">retValue</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;catch...... retValue &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">retValue</span><span class="p">);</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pstmt</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">pstmt</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e1</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;finish......&quot;</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">retValue</span><span class="p">;</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="p" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p041773405712">Run a query statement and retry upon a failure. The number of retry times can be configured.<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_screen64948142581"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
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<span class="normal">49</span></pre></div></td><td class="code"><div><pre><span></span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">ExecPreparedSQL</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">maxRetryTime</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">50</span><span class="p">;</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">time</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span>
<span class="w"> </span><span class="k">do</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">time</span><span class="o">++</span><span class="p">;</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;time:&quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">time</span><span class="p">);</span>
<span class="w"> </span><span class="kt">boolean</span><span class="w"> </span><span class="n">ret</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">QueryRedo</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="k">if</span><span class="p">(</span><span class="n">ret</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="kc">false</span><span class="p">){</span>
<span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">&quot;retry, time:&quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">time</span><span class="p">);</span>
<span class="w"> </span><span class="n">Thread</span><span class="p">.</span><span class="na">sleep</span><span class="p">(</span><span class="mi">10000</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="n">QueryRedo</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="kc">null</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span><span class="n">time</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">maxRetryTime</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="cm">/**</span>
<span class="cm"> * Main process. Call static methods one by one.</span>
<span class="cm"> * @param args</span>
<span class="cm"> * @throws InterruptedException </span>
<span class="cm"> */</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">InterruptedException</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Establish a connection to the database.</span>
<span class="w"> </span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">GetConnection</span><span class="p">(</span><span class="s">&quot;testuser&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;test@123&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Create a table.</span>
<span class="w"> </span><span class="n">CreateTable</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Insert data in batches.</span>
<span class="w"> </span><span class="n">BatchInsertData</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Run the precompilation statement to update data.</span>
<span class="w"> </span><span class="n">ExecPreparedSQL</span><span class="p">(</span><span class="n">conn</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Close the connection to the database.</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">conn</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
</pre></div></td></tr></table></div>
</div>
</div>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p159871953193218"></p>
</div>
<div class="section" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_section176243914330"><h4 class="sectiontitle">Importing and Exporting Data Through Local Files</h4><p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_a79136ca797284d948a4eeae286022381">When the JAVA language is used for secondary development based on <span id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_text7947937">GaussDB(DWS)</span>, you can use the CopyManager interface to export data from the database to a local file or import a local file to the database by streaming. The file can be in CSV or TEXT format.</p>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_en-us_topic_0106303462_p537818945212">The sample program is as follows. Load the <span id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_text1927746232">GaussDB(DWS)</span> JDBC driver before running it.</p>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p13783406714"></p>
<div class="p" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p7782130276"><strong id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_b1042516463613">gsjdbc4.jar</strong> is used as an example.<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_s143da5b6311d42da9f905c046cd3f2c6"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
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<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.DriverManager</span><span class="p">;</span><span class="w"> </span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.io.IOException</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.io.FileInputStream</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.io.FileOutputStream</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.SQLException</span><span class="p">;</span><span class="w"> </span>
<span class="kn">import</span><span class="w"> </span><span class="nn">org.postgresql.copy.CopyManager</span><span class="p">;</span><span class="w"> </span>
<span class="kn">import</span><span class="w"> </span><span class="nn">org.postgresql.core.BaseConnection</span><span class="p">;</span>
<span class="w"> </span>
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Copy</span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span>
<span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">urls</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;jdbc:postgresql://10.180.155.74:8000/gaussdb&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//URL of the database</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">username</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;jack&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//Username</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">password</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;********&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//Password</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">tablename</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;migration_table&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//Define table information.</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">tablename1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;migration_table_1&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//Define table information.</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">driver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;org.postgresql.Driver&quot;</span><span class="p">;</span><span class="w"> </span>
<span class="w"> </span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span>
<span class="w"> </span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">Class</span><span class="p">.</span><span class="na">forName</span><span class="p">(</span><span class="n">driver</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DriverManager</span><span class="p">.</span><span class="na">getConnection</span><span class="p">(</span><span class="n">urls</span><span class="p">,</span><span class="w"> </span><span class="n">username</span><span class="p">,</span><span class="w"> </span><span class="n">password</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="p" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p879104910213">Import and export data.<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_screen1938812491130"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
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<span class="normal">64</span>
<span class="normal">65</span>
<span class="normal">66</span>
<span class="normal">67</span>
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<span class="normal">69</span>
<span class="normal">70</span>
<span class="normal">71</span>
<span class="normal">72</span>
<span class="normal">73</span></pre></div></td><td class="code"><div><pre><span></span><span class="w"> </span><span class="c1">//Export the query result of migration_table to the local file d:/data.txt.</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">copyToFile</span><span class="p">(</span><span class="n">conn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;d:/data.txt&quot;</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;(SELECT * FROM migration_table)&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// TODO Auto-generated catch block</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// TODO Auto-generated catch block</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="c1">//Import data from the d:/data.txt file to the migration_table_1 table.</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">copyFromFile</span><span class="p">(</span><span class="n">conn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;d:/data.txt&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">migration_table_1</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// TODO Auto-generated catch block</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// TODO Auto-generated catch block</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="c1">//Export the data from the migration_table_1 table to the d:/data1.txt file.</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">copyToFile</span><span class="p">(</span><span class="n">conn</span><span class="p">,</span><span class="w"> </span><span class="s">&quot;d:/data1.txt&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">migration_table_1</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// TODO Auto-generated catch block</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// TODO Auto-generated catch block</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">copyFromFile</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">connection</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">filePath</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">tableName</span><span class="p">)</span><span class="w"> </span>
<span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">SQLException</span><span class="p">,</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span>
<span class="w"> </span><span class="n">FileInputStream</span><span class="w"> </span><span class="n">fileInputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span>
<span class="w"> </span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">CopyManager</span><span class="w"> </span><span class="n">copyManager</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyManager</span><span class="p">((</span><span class="n">BaseConnection</span><span class="p">)</span><span class="n">connection</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="n">fileInputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="n">filePath</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="n">copyManager</span><span class="p">.</span><span class="na">copyIn</span><span class="p">(</span><span class="s">&quot;COPY &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">tableName</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot; FROM STDIN&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">fileInputStream</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">fileInputStream</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">fileInputStream</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">copyToFile</span><span class="p">(</span><span class="n">Connection</span><span class="w"> </span><span class="n">connection</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">filePath</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">tableOrQuery</span><span class="p">)</span><span class="w"> </span>
<span class="w"> </span><span class="kd">throws</span><span class="w"> </span><span class="n">SQLException</span><span class="p">,</span><span class="w"> </span><span class="n">IOException</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span>
<span class="w"> </span><span class="n">FileOutputStream</span><span class="w"> </span><span class="n">fileOutputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">null</span><span class="p">;</span><span class="w"> </span>
<span class="w"> </span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">CopyManager</span><span class="w"> </span><span class="n">copyManager</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyManager</span><span class="p">((</span><span class="n">BaseConnection</span><span class="p">)</span><span class="n">connection</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="n">fileOutputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="n">filePath</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="n">copyManager</span><span class="p">.</span><span class="na">copyOut</span><span class="p">(</span><span class="s">&quot;COPY &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">tableOrQuery</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot; TO STDOUT&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">fileOutputStream</span><span class="p">);</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">finally</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">fileOutputStream</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="kc">null</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">fileOutputStream</span><span class="p">.</span><span class="na">close</span><span class="p">();</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span>
<span class="p">}</span>
</pre></div></td></tr></table></div>
</div>
</div>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p1770051023316"></p>
</div>
<div class="section" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_section12809101994811"><h4 class="sectiontitle">Migrating Data from MySQL to <span id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_text141961637154117">GaussDB(DWS)</span></h4><p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_a02b83f0a4e214fdb9d608a621306138c">The following example shows how to use CopyManager to migrate data from MySQL to <span id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_text1658087719">GaussDB(DWS)</span>.</p>
<p id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p121798825013"></p>
<div class="p" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p917912845019"><strong id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_b144362419426">gsjdbc4.jar</strong> is used as an example.<div class="codecoloring" codetype="Java" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_s64720293e41e4573a8039a2ff56dd019"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
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<span class="normal">67</span></pre></div></td><td class="code"><div><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">java.io.StringReader</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.Connection</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.DriverManager</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.ResultSet</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.SQLException</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">java.sql.Statement</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">org.postgresql.copy.CopyManager</span><span class="p">;</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">org.postgresql.core.BaseConnection</span><span class="p">;</span>
<span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">Migration</span><span class="p">{</span>
<span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="n">String</span><span class="o">[]</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">url</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;jdbc:postgresql://10.180.155.74:8000/gaussdb&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//URL of the database</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">user</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;jack&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//GaussDB(DWS) username</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">pass</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;********&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//GaussDB(DWS) password</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">tablename</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;migration_table&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//Define table information.</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">delimiter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;|&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//Define a delimiter.</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">encoding</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">String</span><span class="p">(</span><span class="s">&quot;UTF8&quot;</span><span class="p">);</span><span class="w"> </span><span class="c1">//Define a character set.</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">driver</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;org.postgresql.Driver&quot;</span><span class="p">;</span>
<span class="w"> </span><span class="n">StringBuffer</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringBuffer</span><span class="p">();</span><span class="w"> </span><span class="c1">//Define the buffer to store formatted data.</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Obtain the query result set of the source database.</span>
<span class="w"> </span><span class="n">ResultSet</span><span class="w"> </span><span class="n">rs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getDataSet</span><span class="p">();</span>
<span class="w"> </span><span class="c1">//Traverse the result set and obtain records row by row.</span>
<span class="w"> </span><span class="c1">//The values of columns in each record are separated by the specified delimiter and end with a newline character to form strings.</span>
<span class="w"> </span><span class="c1">////Add the strings to the buffer.</span>
<span class="w"> </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">rs</span><span class="p">.</span><span class="na">next</span><span class="p">())</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="na">append</span><span class="p">(</span><span class="n">rs</span><span class="p">.</span><span class="na">getString</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">delimiter</span>
<span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">rs</span><span class="p">.</span><span class="na">getString</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">delimiter</span>
<span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">rs</span><span class="p">.</span><span class="na">getString</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">delimiter</span>
<span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">rs</span><span class="p">.</span><span class="na">getString</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span>
<span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot;\n&quot;</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="n">rs</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">//Connect to the target database.</span>
<span class="w"> </span><span class="n">Class</span><span class="p">.</span><span class="na">forName</span><span class="p">(</span><span class="n">driver</span><span class="p">);</span>
<span class="w"> </span><span class="n">Connection</span><span class="w"> </span><span class="n">conn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">DriverManager</span><span class="p">.</span><span class="na">getConnection</span><span class="p">(</span><span class="n">url</span><span class="p">,</span><span class="w"> </span><span class="n">user</span><span class="p">,</span><span class="w"> </span><span class="n">pass</span><span class="p">);</span>
<span class="w"> </span><span class="n">BaseConnection</span><span class="w"> </span><span class="n">baseConn</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">BaseConnection</span><span class="p">)</span><span class="w"> </span><span class="n">conn</span><span class="p">;</span>
<span class="w"> </span><span class="n">baseConn</span><span class="p">.</span><span class="na">setAutoCommit</span><span class="p">(</span><span class="kc">false</span><span class="p">);</span>
<span class="w"> </span><span class="c1">//Initialize table information.</span>
<span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">sql</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">&quot;Copy &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">tablename</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot; from STDIN DELIMITER &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot;'&quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">delimiter</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot;'&quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot; ENCODING &quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot;'&quot;</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">encoding</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">&quot;'&quot;</span><span class="p">;</span>
<span class="w"> </span><span class="c1">//Submit data in the buffer.</span>
<span class="w"> </span><span class="n">CopyManager</span><span class="w"> </span><span class="n">cp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">CopyManager</span><span class="p">(</span><span class="n">baseConn</span><span class="p">);</span>
<span class="w"> </span><span class="n">StringReader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">StringReader</span><span class="p">(</span><span class="n">buffer</span><span class="p">.</span><span class="na">toString</span><span class="p">());</span>
<span class="w"> </span><span class="n">cp</span><span class="p">.</span><span class="na">copyIn</span><span class="p">(</span><span class="n">sql</span><span class="p">,</span><span class="w"> </span><span class="n">reader</span><span class="p">);</span>
<span class="w"> </span><span class="n">baseConn</span><span class="p">.</span><span class="na">commit</span><span class="p">();</span>
<span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="n">baseConn</span><span class="p">.</span><span class="na">close</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">ClassNotFoundException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">SQLException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">(</span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">Exception</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span>
</pre></div></td></tr></table></div>
</div>
</div>
<div class="p" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_p647631145411">Return the query result from the source database.<pre class="screen" id="EN-US_TOPIC_0000002043982200__en-us_topic_0000001233563135_screen9291131145412"> private static ResultSet getDataSet() {
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection conn = DriverManager.getConnection("jdbc:mysql://10.119.179.227:3306/jack?useSSL=false&amp;allowPublicKeyRetrieval=true", "jack", "********");
Statement stmt = conn.createStatement();
rs = stmt.executeQuery("select * from migration_table");
} catch (SQLException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return rs;
}
}</pre>
</div>
</div>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_04_0088.html">JDBC-Based Development</a></div>
</div>
</div>
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