问题描述

今天在开发中遇到一奇怪问题，有一个action，在该action里使用request.setAttribute()方法将一个List类型对象放在request中，然后forward到一个jsp文件，该文件的主要内容是使用<logic:iterate>标签将这个List对象中的条目列表显示。与它同样逻辑但位于另一模块（teacher）中的代码执行正常。但这个模块（xxgl）中的代码，本来很简单的逻辑，却总是提示：

org.apache.jasper.JasperException: Cannot find bean t in any scope 
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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684) 
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:432) 
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:356) 
at org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1069) 
at org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:455) 
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:279) 
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482) 
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:507) 
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 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:2417) 
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:193) 
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:781) 
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:549) 
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:589) 
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:666) 
at java.lang.Thread.run(Unknown Source) 

将<logic:iterate>之间的代码去掉后就不会提示错误了，所以怀疑是<bean:write>中的代码有错误。相关文件ListSfzxJbxxAction.java中的execute方法如下：

public ActionForward execute(ActionMapping mapping, ActionForm form, 
   HttpServletRequest request, HttpServletResponse response) throws Exception {

   HibernateDAO dao = HibernateDAO.getInstance(getServlet().getServletContext()); 
   List sfzxjbxxs = dao.find("from " + SfzxJbxx.class.getName()); 
   SfzxJbxx tmp = new SfzxJbxx(); 
   tmp.setSfzxid("id"); 
   tmp.setXxdm("pku"); 
   sfzxjbxxs.add(tmp); 
   request.setAttribute("sfzxjbxxs", sfzxjbxxs); 
   return mapping.findForward("success"); 
} 

listsfzxjbxx.jsp内容如下：

<%@ page contentType="text/html;charset=UTF-8" language="java" %> 
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean"%> 
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html"%> 
<head> 
      <title>SfzxJbxxList</title> 
</head> 
<body> 
<logic:iterate  name="sfzxjbxxs" id="sfzxjbxx"> 
  <tr> 
    <td align="left"> 
      <bean:write name="sfzxjbxx" property="sfzxId" filter="true"/> 
    </td> 
    <td align="left"> 
      <bean:write name="sfzxjbxx" property="xxdm" filter="true"/> 
    </td> 
    <td> 
    </td> 
  </tr> 
</logic:iterate> 
<body> 
</html> 

模块配置文件中相关内容如下：

<action-mappings> 
    <action 
        attribute="Form" 
        input="/form/sfzxjbxx.jsp" 
        name="sfzxJbxxForm" 
        path="/saveSfzxJbxx" 
        type="edu.pku.cc.sfzx.xxgl.action.SaveSfzxJbxxAction" /> 
    <action path="/listsfzxjbxx" type="edu.pku.cc.sfzx.xxgl.action.ListSfzxJbxxAction"> 
        <forward name="success" path="/form/listsfzxjbxx.jsp"/> 
    </action> 

</action-mappings> 

问题解决

经过三个小时的检查，发现是listsfzxjbxx.jsp里缺少<logic:iterate>标签的声明，在前面增加上：

<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic"%> 

一切OK！

搬家前链接：https://www.cnblogs.com/bjzhanghao/archive/2004/07/28/28065.html