摘要：
//初始化连接池相关参数static｛try｛dataSource=newComboPooledDataSource（）；552）java.util.TimerThread.run（Timer.java:
一个项目通过c3p0获得连接池，相关代码如下：
public class JdbcUtil {
// 连接池的核心类
private static ComboPooledDataSource dataSource;
//初始化连接池相关参数
static{
try {
dataSource = new ComboPooledDataSource();
dataSource.setDriverClass(PropertiesUtil.getValue("jdbcName"));
dataSource.setJdbcUrl(PropertiesUtil.getValue("dbUrl"));
dataSource.setUser(PropertiesUtil.getValue("dbUserName"));
dataSource.setPassword(PropertiesUtil.getValue("dbPassword"));
dataSource.setInitialPoolSize(5);
dataSource.setMinPoolSize(5);
dataSource.setMaxPoolSize(20);
// 以下两句用于设置自动重连
dataSource.setIdleConnectionTestPeriod(10);
dataSource.setTestConnectionOnCheckin(true);
} catch (Exception e) {
e.printStackTrace();
}
}
//下面是getDataSource,getConnection等方法
}
关闭Tomcat的时候提示可能会造成内存泄漏：
警告: The web application [uavmonitor] appears to have started a thread named [Timer-0] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.util.TimerThread.mainLoop(Timer.java:552)
java.util.TimerThread.run(Timer.java:505)
二月 13, 2017 3:51:45 下午 org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
警告: The web application [uavmonitor] appears to have started a thread named [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
二月 13, 2017 3:51:45 下午 org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
警告: The web application [uavmonitor] appears to have started a thread named [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
二月 13, 2017 3:51:45 下午 org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
警告: The web application [uavmonitor] appears to have started a thread named [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
主要是这句：
警告: The web application [uavmonitor] appears to have started a thread named [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
与这句
The web application [uavmonitor] appears to have started a thread named [Timer-0] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.util.TimerThread.mainLoop(Timer.java:552)
java.util.TimerThread.run(Timer.java:505)
查询c3p0官方文档
说明如下：c3p0 spawns a variety of Threads (helper threads, java.util.Timer threads)，结合上面的出错信息，推断应该是Tomcat关闭的时候没有关闭JdbcUtil类创建出来的c3p0的datasource。
解决方案
写一个监听器，在其public void contextDestroyed方法中进行对c3p0数据源进行关闭就可以解决相关问题。
try {
DataSources.destroy(JdbcUtil.getDataSource());//getDataSource方法获取c3p0数据源
System.out.println("关闭数据库连接池成功!");
} catch (SQLException e) {
e.printStackTrace();
}
如果运行在Tomcat中的代码启动了Executor线程池，也需要在适当的地方(比如监听器中的contextDestroyed方法)进行shutdown，否则会造成资源泄露。
从这个例子中也可以看出，直接使用spring、mybatis等管理数据源是多么省事。