servlet重定向问题

Question

IE看到的错误：
description The server encountered an internal error (Internal Server Error) that prevented it from fulfilling this request.exception java.lang.NullPointerException
 at javax.servlet.GenericServlet.getServletContext(GenericServlet.java:204)
 at tservelt.MyServlet.doProcess(MyServlet.java:43)
 at tservelt.MyServlet.doGet(MyServlet.java:26)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
 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 tservelt.TTFilter.doFilter(TTFilter.java:26)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
 at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
 at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
 at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
 at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
 at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
 at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2347)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
 at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
 at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
 at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
 at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
 at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
 at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
 at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1027)
 at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1125)
Jb看到的错误：
StandardWrapperValve[myservlet]: Servlet.service() for servlet myservlet threw exceptionjava.lang.NullPointerExceptionjava.lang.NullPointerException at javax.servlet.GenericServlet.getServletContext(GenericServlet.java:204) at tservelt.MyServlet.doProcess(MyServlet.java:43) at tservelt.MyServlet.doGet(MyServlet.java:26) at javax.servlet.http.HttpServlet.service(HttpServlet.java:740) 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 tservelt.TTFilter.doFilter(TTFilter.java:26) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2347) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1027) at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1125) at java.lang.Thread.run(Thread.java:536)

Answer 1

RequestDispatcher rd=this.getServletContext().getRequestDispatcher(url);
应该是这个地方有问题。你好好看看。

Answer 2

at tservelt.MyServlet.doProcess(MyServlet.java:43)
是什么？
另外，请确认/index.jsp确实存在。

Answer 3

是RequestDispatcher rd=this.getServletContext().getRequestDispatcher(url);
这个地方有错，但错在那里呢？index.jsp存在，是不目录上位置问题?

Answer 4

this.getServletContext()我怀疑这个地方是null你在测试一下

Answer 5

在servlet里定义如下转向方法，  private void dispatch(HttpServletRequest req, HttpServletResponse res,
                        String url) throws ServletException, IOException {
    RequestDispatcher rd = getServletContext().getRequestDispatcher(url);
    rd.forward(req, res);
  }然后在doPost中调用
      dispatch(req, res, "/result.jsp");你也可以直接在doPost中转向

Answer 6

你报的空指针异常，可能你的页面不存在。或者在RequestDispatcher rd = getServletContext().getRequestDispatcher(url);的时候没有找到该页

Answer 7

err = URLEncoder.encode("Success！");
    response.sendRedirect("/yj/ypmanage/test.jsp?err="+err+"&id="+id);
这样就行

Answer 8

已经揭贴了，问题还没解决吗？
可以先判断是否为空：
RequestDispatcher dispatcher=getServletContext().getRequestDispatcher("/jsp/"+page+".jsp");      
if (dispatcher!=null)          
    dispatcher.forward(request,response);
你的页面大概不存在，"/index.jsp"是指根目录下的文件
是不是文件的路径不对？