关于mysql：尝试从maven运行java程序时出现异常

Exception while trying to run java program from maven

我有一个小型 java 程序，它连接到 mysql 数据库并从中读取数据。我可以使用 java -cp 成功运行它，但是当我尝试使用 mvn exec:java 运行它时，程序完成后出现此异常：

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[WARNING] thread Thread[MySQL Statement Cancellation Timer,5,com.mycompany.mydivision.App] was interrupted but is still alive after waiting at least 15000msecs
[WARNING] thread Thread[MySQL Statement Cancellation Timer,5,com.mycompany.mydivision.App] will linger despite being asked to die via interruption
[WARNING] NOTE: 1 thread(s) did not finish despite being asked to via interruption. This is not a problem with exec:java, it is a problem with the running code. Although not serious, it should be remedied.
[WARNING] Couldn't destroy threadgroup org.codehaus.mojo.exec.ExecJavaMojo$IsolatedThreadGroup[name=com.mycompany.mydivision.App,maxpri=10]
java.lang.IllegalThreadStateException
at java.lang.ThreadGroup.destroy(ThreadGroup.java:775)
at org.codehaus.mojo.exec.ExecJavaMojo.execute(ExecJavaMojo.java:328)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:862)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:197)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)

为什么会发生这种情况，我该如何解决？这是我的代码以备不时之需：

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public class App
{

public static void main( String[] args )
{
try (JdbcReader reader = new JdbcReader())
{
reader.test();
}
catch (SQLException ex) {
// handle any errors
System.out.println("SQLException:" + ex.getMessage());
System.out.println("SQLState:" + ex.getSQLState());
System.out.println("VendorError:" + ex.getErrorCode());
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
package com.mycompany.mydivision;

import com.vividsolutions.jts.geom.Geometry;

import java.io.Closeable;
import java.io.InputStream;
import java.sql.*;

/**
*
*/
public class JdbcReader implements Closeable{

Connection conn;

public JdbcReader() throws ClassNotFoundException, SQLException, IllegalAccessException, InstantiationException
{
// The newInstance() call is a work around for some
// broken Java implementations
Class.forName("com.mysql.jdbc.Driver").newInstance();
this.conn = DriverManager.getConnection("jdbc:mysql://localhost/mydb?user=guest");
}

/**
* https://dev.mysql.com/doc/connector-j/en/connector-j-usagenotes-statements.html
*/
public void test() throws Exception
{
Statement stmt = null;
ResultSet rs = null;
try {
stmt = this.conn.createStatement();
if (stmt.execute("SELECT * FROM mydb.my_table limit 20")) {
rs = stmt.getResultSet();
// Fetch each row from the result set
while (rs.next()) {
String name = rs.getString("name");
String description = rs.getString("Descr");

System.out.printf("%s\\t%s\
", name, description);
}
}
}
finally {
// it is a good idea to release
// resources in a finally{} block
// in reverse-order of their creation
// if they are no-longer needed

if (rs != null) {
try {
System.out.println("closing ResultSet");
rs.close();
} catch (SQLException sqlEx) { } // ignore

rs = null;
}

if (stmt != null) {
try {
System.out.println("closing Statement");
stmt.close();
} catch (SQLException sqlEx) { } // ignore

stmt = null;
}
}
}

public void close()
{
if (conn != null)
{
try {
System.out.println("closing connection");
conn.close();
}
catch (SQLException ex) { } // ignore
conn = null;
}
}
}

相关讨论

在 exec maven 插件中试试这个

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<configuration>
<mainClass>com.test.Startup</mainClass>
<cleanupDaemonThreads>false</cleanupDaemonThreads>
</configuration>

相关讨论

我找到了一个稍微不同的解决方案。我有一个类似的错误，我猜更改 Maven 配置会修复它，但我想看看我是否可以先修复错误本身；)。事实证明，我所需要的只是在我的主要方法结束时调用 System.exit(status) 并解决了问题。我猜 exec 插件需要显式调用 System.exit(在其他活动线程上类似)才能正常运行。

相关讨论

在程序的最后一行显式使用 System.exit(0); 来解决这个问题。

相关讨论