? 写了一个应用，运行平台为Tomcat，技术很基本，就是jsp+javabean
?
? 上线半年多，用户一直使用正常,最近突然频频出错，而且从错误中看不到任何有帮助的信息！而且最为奇怪的是当出错后按下刷新键，程序往往可以继续运行。

? 需要注意的2点：
? 1.程序原来肯定是没有问题的
? 2.刷新下就能执行。
?
? issue_next.jsp是个很简单的对数据进行插入数据库操作的页面。
?
? 错误信息如下（我觉得好像没什么有价值的东西）：
?
? 2004-11-17 16:22:58 StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception
? org.apache.jasper.JasperException
? at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:254)
? at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
? at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
? at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
? at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
? at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
? at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
? at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
? at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
? at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
? at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
? at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
? at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
? at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
? at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2415)
? at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
? at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
? at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
? at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
? at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
? at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
? at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
? at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
? at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
? at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
? at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
? at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
? at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
? at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:594)
? at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:392)
? at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
? at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619)
? at java.lang.Thread.run(Thread.java:536)
? ----- Root Cause -----
? javax.servlet.ServletException
? at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:536)
? at org.apache.jsp.issue_parts_jsp._jspService(issue_parts_jsp.java:431)
? at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
? at javax.servlet.http.HttpServlet.service(Htt