分享一个使用c3p0,tomcat报内存逸出的解决方案

http://stackoverflow.com/questions/3320400/to-prevent-a-memory-leak-the-jdbc-driver-has-been-forcibly-unregistered
/**
 * @author Aray Chou
 *         Email: Aray(dot)Chou(dot)CN(at)gmail(dot)com
 *         Replace "(dot)" with "." and replace "(at)" with "@"
 */
import  javax.servlet.ServletContextEvent;
import  javax.servlet.ServletContextListener;
import  javax.servlet.annotation.WebListener;
import  javax.sql.DataSource;

import  com.mchange.v2.c3p0.DataSources;

/**
 * C3P0连接池在context关闭的时候（关闭tomcat服务器或者reload context），不会回收资源，导致内存泄露。Tomcat会报如下错误：
 * <br />SEVERE: The web application [/xxx] appears to have started a thread named [com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1] but has failed to stop it. This is very likely to create a memory leak.
 *
 * 本类在context关闭的时候释放c3p0连接池，解决此类存泄露问题。
 *
 * 另外，JDBC驱动包(例如ojdbc6.jar)放在$TOMCAT_HOME/lib下面，不要放在WEB-INF/lib里，可以解决JDBC驱动导致内存泄露的问题。此时Tomcat报如下错误:
 * SEVERE: A web application registered the JBDC driver [oracle.jdbc.OracleDriver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
 */
@WebListener ()
public  class  DBCloser  implements  ServletContextListener {

    /*
     * (non-Javadoc)
     *
     * @see
     * javax.servlet.ServletContextListener#contextInitialized(javax.servlet
     * .ServletContextEvent)
     */
    @Override
    public void contextInitialized(ServletContextEvent sce) {
    }

    /*
     * (non-Javadoc)
     *
     * @see javax.servlet.ServletContextListener#contextDestroyed(javax.servlet.
     * ServletContextEvent)
     */
    @Override
    public  void  contextDestroyed(ServletContextEvent sce) {

        //TODO 这里需要修改一下，得到dataSource
        DataSource dataSource =  null ;

        try
        {
            //调用c3p0的关闭数据库连接的方法
            DataSources.destroy(dataSource);
        }
        catch  (Exception e)
        {
            e.printStackTrace();
        }


        //等待连接池关闭线程退出，避免Tomcat报线程未关闭导致memory leak的错误
        try  {
            Thread.sleep( 1000 );
        }  catch  (InterruptedException e) {
            e.printStackTrace();
        }
    }

}