如题，
错误页面如下显示

error.jsp页面显示如下：（我新建一个jsp页面，却并不会出现上述图片的问题，很奇怪啊）
HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException

org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:358)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)

root cause

java.lang.NullPointerException

org.apache.jsp.Error_jsp._jspService(Error_jsp.java:42)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)

note The full stack trace of the root cause is available in the Tomcat logs.

Apache Tomcat/5.0.16

tomcatlog 中的日志为 ：
2016-08-12 06:35:29 StandardContext[/jsp-examples]ContextListener: contextInitialized()
2016-08-12 06:35:29 StandardContext[/jsp-examples]SessionListener: contextInitialized()
2016-08-12 06:35:29 StandardContext[/servlets-examples]ContextListener: contextInitialized()
2016-08-12 06:35:29 StandardContext[/servlets-examples]SessionListener: contextInitialized()
2016-08-12 06:36:12 StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException

at org.apache.jsp.Error_jsp._jspService(Error_jsp.java:42)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:284)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:204)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:564)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:245)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:199)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:564)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:195)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:164)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:564)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:156)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:564)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:972)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:211)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:805)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:696)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:605)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:677)
at java.lang.Thread.run(Unknown Source)

%>
ERROR.JSP
<%@ page
language = "java"
isErrorPage = "true"
contentType = "text/html; charset=gb2312"
%>

    
错误信息
    
 
    
<%=exception.toString()%>
    
 
    
返回上一页
    
 

LOGIN.JSP
<%@ page
info = "用户登陆的 jsp"
errorPage = "Error.jsp"
contentType = "text/html; charset=gb2312"
import = "java.io.*"
import = "java.util.*"
import = "java.sql.*"
import = "qesuite.*"
%>

<%--实例化DBConnection对象dbConnection：建立连接池，预先建立三个数据库连接--%>

<%--实例化DBBridge对象dbBridge--%>

<%--实例化Project对象project--%>

<%

    if (!session.isNew ()) {
      session.removeAttribute("id");
      session.removeAttribute("password");
    }

%>

<%--from gsh,to enable these codes Security Level of IE's must be down.--%>
<%-- --%>

<%--from gsh--%>

<%

  //查询Project得到项目信息
  project.loadData(0, 1);

%>

用户登陆             选择项目:   <% Vector vQID = new Vector(); Vector vName = new Vector(); vQID = project.getvQID(); vName = project.getvPrjName(); if (vQID != null){ Enumeration enumid = vQID.elements(); Enumeration enumname = vName.elements(); while(enumid.hasMoreElements()) { String sId = (String) enumid.nextElement(); String sName = (String) enumname.nextElement(); %> ><%= sName%> <% } } %> 帐　　号:   密　　码:

<%

    dbBridge.closeBridge ();

%>