下列异常是什么原因引起的？

[yiyky]

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
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.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2416)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$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$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:601)
at org.apache.coyote.http11.Http11Protocol$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

java.lang.NullPointerException
at org.apache.jsp.sysmodelEdit_jsp._jspService(sysmodelEdit_jsp.java:58)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:210)
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.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2416)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$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$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:601)
at org.apache.coyote.http11.Http11Protocol$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)



--------------------------------------------------------------------------------

Apache Tomcat/4.1.27

[singnet]

先判断一下request.getParameter("Username")是否为空

[yiyky]

我的sysmodelEdit.jsp:


<%@ page contentType="text/html; charset=gb2312" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>系统模块信息管理</title>
<!--link rel="stylesheet" href="../css/mail_style.css"-->
<%@ page import="zd_oa.*,java.sql.*,java.util.*" %>
<script language="javascript">
function DeleteUser(var strUrl)
{
if (window.confirm("Delete it really?"))
{
window.location.href = strUrl;
return ture;
}
else
{
return false;
}
}

function Addinfo()
{
<% String addinfo;
addinfo="";
try{
addinfo = request.getParameter("Addinfo");
}catch(Exception e){}
if (addinfo.equals("AddError"))
{
System.out.print("window.alert(\"have the same ID\");");
}
if (addinfo.equals("DoelseError"))
{
System.out.print("window.alert(\"You input the error id\");");
}
if (addinfo.equals("Addok"))
{
System.out.print("window.alert(\"have the same ID\");");
}
%>
}
</script>
</head>
<body topmargin="20">
<jsp:useBean id="yykoperationB" class="zd_oa.YYKoperation" scope="session" />
<%
String UserID;
String Username;
ResultSet rs;
ResultSet rs1;
ResultSet rs2;
String Sqlstr;
String SqlstrC;
Sqlstr="select Modelid,Modelname,Parentid,bz from SYmodel order by Modelid";
%>
<div align="center">
<table border=５0>
系统模块管理 color="#804040">10</font>  
<br>
操作员：<%=request.getParameter("Username")%><font color="#804040">1</font> <br>
</td>
</tr>
</table>
</div>
<div align="center" width="100%">
<table border="0" width="100%">
<tr valign="top">
<td width="100%">
系统模块信息列表
</tr>
<tr>

<tbody>
<tr bgcolor="#B03A00" align=center>
<td width="15%"><font color=white>模块ID</font></td>
<td width="15%"><font color=white>模块名称</font></td>
<td width="15%"><font color=white>所属模块</font></td>
<td width="40%"><font color=#FFCC33>备注</font></td>
<td nowrap><font color=white>删除</font></td>
</tr>
<%
try{rs=yykoperationB.returnsql(Sqlstr);

while (rs.next()){
System.out.print("<tr>");

System.out.print("<td >");
System.out.print(rs.getString("Modelid"));
System.out.print("</td>");

System.out.print("<td>");
System.out.print(rs.getString("Modelname"));
System.out.print("</td>");

System.out.print("<td>");
SqlstrC="select Modelname from User where Modelid='" + rs.getString("Groupid") + "'";
rs2=yykoperationB.returnsql(SqlstrC);
ResultSetMetaData rsmd = rs.getMetaData();
if (rsmd.getColumnCount()>=1) {
System.out.print(rs2.getString("Modelname"));}
System.out.print("</td>");

System.out.print("<td>");
System.out.print(rs.getString("Bz"));
System.out.print("</td>");

System.out.print("<td>");
System.out.print("<input type=\"submit\" name=\"submit\" value=\"Delete\" onclick = \"DeleteUser('Deluser.jsp?ID=" + rs.getString("Modelid") + "')\" >");
System.out.print("</td>");

System.out.print("</tr>");
}

}catch(Exception e ){System.out.print(e.getMessage() );}
%>
</tbody>
</table>
</tr>
</div>
<div align="center" width="100%" >
<table align="center" width="100%">
</tr>
<center>
<form name="SymodelEdit" method="post" action="Addmodel.jsp">
程序ＩＤ:<input type="Text" name="Modelid" size="10%"> >
程序名称:<input type="Text" name="Modelname" size="20%" >
所属模块:<input type="text" name="Parentid" size="10%">
备注：<input type="text" name="Bz" size="40%">
<br>
<input type="submit" name="ADD" value="新建程序/模块">
<input type="reset" name="reset" value="重新设置">
</form>
</center>
</table>
</div>
</body>
</html>