tomcat压力测试问题，高手们请来

760176104

我刚给自己的一个网站做了几次压力测试（40并发数并且持续一段时间），我用的是自己的数据连接池，
每次测试刚开始都没有问题，可一段时间以后就会抛出异常，每次异常都不一样
随后就会发现连接池的连接数会不断增加而不释放掉，还会抛出内存溢出问题，请大家帮我分析下这个是什么问题？有什么办法可以监控一下，小弟我先谢谢大家了！
另外tomcat的虚拟内存我加到了512－768M了。
下面是最近出的异常：
FreeConnectionPool=20
javax.servlet.ServletException
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:244)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:704)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:474)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:409)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
at com.admin.TP.UserCXSJ.doPost(UserCXSJ.java:72)
at com.admin.TP.UserCXSJ.doGet(UserCXSJ.java:45)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:534)