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Lu, Huayi e6fa411af0 DWS DEV 830.201 version 
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com>
Co-authored-by: Lu, Huayi <luhuayi@huawei.com>
Co-committed-by: Lu, Huayi <luhuayi@huawei.com>
2024-05-16 07:24:04 +00:00

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<a name="EN-US_TOPIC_0000001188323626"></a><a name="EN-US_TOPIC_0000001188323626"></a>
<h1 class="topictitle1">Example: Retrying SQL Queries for Applications</h1>
<div id="body1526461869884"><p id="EN-US_TOPIC_0000001188323626__a51af6c623abc43deb9a68807ad0856d2">If the primary DN is faulty and cannot be restored within 40s, its standby is automatically promoted to primary to ensure the normal running of the cluster. Jobs running during the failover will fail and those started after the failover 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>
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<span class="normal">198</span></pre></div></td><td class="code"><div><pre><span></span><span class="c1">//gsjdbc4.jar is used as an example.</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>
<span class="w"> </span>
<span class="w"> </span><span class="c1">//Run an ordinary SQL statement. Create a jdbc_test1 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">// 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>
<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 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">//Perform 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="w"> </span><span class="c1">//Run the precompilation statement to update data.</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;finesh......&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="c1">//Run a query statement and retry upon a failure. The number of retry times can be configured.</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">//Disconnect from 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>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_04_0088.html">JDBC-Based Development</a></div>
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