加入了struts标签的一个错误，高手指点

Question

java.lang.ClassCastException
org.apache.jsp.member.addelective_jsp._jspService(addelective_jsp.java:276)
下面就是org.apache.jsp.member.addelective_jsp._jspServiceif (_jspx_eval_logic_iterate_0 != javax.servlet.jsp.tagext.Tag.EVAL_BODY_INCLUDE) {
                  out = _jspx_page_context.pushBody();
                  _jspx_th_logic_iterate_0.setBodyContent((javax.servlet.jsp.tagext.BodyContent) out);
                  _jspx_th_logic_iterate_0.doInitBody();
                }
 这是276行              result = (com.edu.elective.form.ElectiveForm) _jspx_page_context.findAttribute("result");
                index = (java.lang.Integer) _jspx_page_context.findAttribute("index");
                do {
                  out.write("\r\n");
                  out.write("\t\t  <tr  height=18>\r\n");

Answer 1

这个是个ClassCastException，也就是类强制转型的异常，_jspx_page_context.findAttribute("result");返回的对象不是com.edu.elective.form.ElectiveForm。你可以在jsp中用System.out打印一下result是什么对象。

Answer 2

标准的强制类型转化错误。建议贴出你的action,from和jsp文件。

Answer 3

action文件package com.edu.elective.action;import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;import com.edu.common.LoginConstants;
import com.edu.common.UserSessionManager;
import com.edu.common.WebConstant;
import com.edu.dao.hibernate.EduHibernateException;
import com.edu.merchant.model.Merchants;
import com.edu.struts.action.BaseAction;
import com.edu.elective.form.ElectiveForm;
import com.edu.elective.impl.ElectiveManagerFactory;
import com.edu.vo.PageListVO;
import com.edu.vo.QueryVO;public class QueryElectiveAction extends BaseAction {
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

ElectiveForm pForm = (ElectiveForm) form;
String returnStr = WebConstant.FORWARD_INITPAGE;
String userSession = null;

try {
PageListVO rvo=null;
Map map = new HashMap(request.getParameterMap());
HttpSession session = request.getSession();
userSession = UserSessionManager.checkUserSession(request);
if(null == userSession){
return new ActionForward("/loginfail.jsp");
}
if (null != userSession && session.getAttribute("isNumber").equals("2")){
Merchants m = (Merchants) session.getAttribute(LoginConstants.GLOBLE_LOGINVO);
map.put("Merchants",m);
}
QueryVO qvo=new QueryVO();
qvo.setScatterMap(map);
qvo.setPageSize(WebConstant.PAGENUMBER); qvo.setCurPage(pForm.getPageNum());
rvo=(PageListVO)ElectiveManagerFactory.getElectiveManager().findAllElective1(qvo);
ArrayList ListResult = (ArrayList) rvo.getretVO();
            setQueryResult(rvo, pForm); 
            request.setAttribute(WebConstant.RETURN_LIST, ListResult);
} catch (EduHibernateException e) {
e.printStackTrace();
return mapping.findForward(WebConstant.FORWARD_FAIL);
}
request.setAttribute(WebConstant.PAGE_Object, pForm);
return mapping.findForward(returnStr);
}

}

Answer 4

form文件package com.edu.elective.form;import com.edu.struts.form.BaseForm;public class ElectiveForm extends BaseForm {
    private String id;
    private String coursetype;
    private String coursename;
    private String videoid;
    private String realname;   public ElectiveForm() {
   }   public ElectiveForm(String id, String coursename, String coursetype, String videoid, String realname) {
       this.id = id;
       this.coursetype = coursetype;
       this.coursename = coursename;
       this.videoid =  videoid;
       this.realname = realname;
   }public String getCoursename() {
return coursename;
}public void setCoursename(String coursename) {
this.coursename = coursename;
}public String getCoursetype() {
return coursetype;
}public void setCoursetype(String coursetype) {
this.coursetype = coursetype;
}public String getId() {
return id;
}public void setId(String id) {
this.id = id;
}public String getVideoid() {
return videoid;
}public void setVideoid(String videoid) {
this.videoid = videoid;
}public String getRealname() {
return realname;
}public void setRealname(String realname) {
this.realname = realname;
}

}

Answer 5

addelective.jsp文件<%@ page contentType="text/html; charset=gb2312" %>
<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/struts-edu.tld" prefix="edu"%>
<%@include file="/admin/checksession.jsp"%>
<html>
<head>
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<script src="js/common.js" language=javascript></script>
<script src="js/Calendar.js" language=javascript></script>
<script src="js/popwin.js" language=javascript></script>
<script src="js/checkForm.js" language=javascript></script>
<script language="javascript">
function Page(pageNum){
if(checkNum(pageNum)==0) {
    alert("要跳转的页数必须是大于0的数字！");
    return;
}

var page_objForm=document.forms[0];
page_objForm.pageNum.value= pageNum;
        page_objForm.action="<%=request.getContextPath()%>/addelective.do";
        page_objForm.target="";
page_objForm.submit();
}function views(threm,id) {
var url = "<%=request.getContextPath()%>/member/viewuselogin.do?id="+id;
window.open(url);
}function douser(id) {
 var theForm=document.forms[0];
 var count=0;
 for (var k = 0; k < theForm.length; k++)
 if ((theForm[k].type == "checkbox") && (theForm[k].checked))
count++;
 if (count==0) {
alert("请选择你要选学的课程！");
return false;
 } else {
 if(window.confirm("确定要这样做了吗？"))  {
theForm.action="<%=request.getContextPath()%>/addelective.do?realname="+realname;
theForm.submit();
 }
 else
return false;
 }
}function getOperationForm(){
var tmpform=document.all("pageObject");
var tmpErrMsg="";
if(tmpform==null){
tmpErrMsg="没有查询记录!";
alert(tmpErrMsg);
}
return tmpform;
}function selectAll(){
var tmpform=getOperationForm();
if(tmpform==null){
return ;
}
var tmpEles=tmpform.all("checkbox");
if(tmpEles.length==null){
tmpEles.checked=true;
return ;
}

for(var tmpi=0;tmpi<tmpEles.length;tmpi++){
tmpEles(tmpi).checked=true;
}

}
function customSubmit(pInput,pURL)
{
var theForm=document.forms[0];
theForm.pageNum.value=1;
theForm.submit();
}
</script><title>学员信息查看</title>
<link href="css/YES.css" rel="stylesheet" type="text/css">
</head>
<body>
<html:form name="pageObject" action="/addelective" type="com.edu.elective.form.ElectiveForm"  scope="request">
<input type="hidden" name="isuser" value="1">
<table width="90%"  border="1" align="center" cellpadding="0" bordercolor="#9C9AFF" bgcolor="#DEDFFF">
  <tr height=18 bgcolor="">
   <td height="18" colspan="2" align=center>选课</td>
   <td width="11%" align=center>课程ID</td>
    <td width="39%" align=center>课程名</td>
    <td width="17%" align=center>课程类型</td>
    <td width="16%" align=center>删除</td>
  </tr>
<logic:empty name="listresult">
  <tr height=18>
    <td colspan="2">&nbsp;</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
  </tr>
</logic:empty>
<logic:notEmpty name="listresult">
   <logic:iterate id="result" name="listresult" indexId="index" type="com.edu.elective.form.ElectiveForm">
  <tr  height=18>
   <td colspan="2" align=center><input type="checkbox" name="checkbox" value="<bean:write name="result" property="id"/>"></td>
    <td align=center><bean:write name="result" property="id"/></td>
    <td align=center><bean:write name="result" property="coursename"/></td>
    <td align=center><bean:write name="result" property="coursetype"/></td>
    <td align=center><!--a href="#" onClick="removeTest('<bean:write name="result" property="id"/>')" -->删 除<!--/a--></td>
   </tr>
   </logic:iterate>
</logic:notEmpty>
   <tr>
    <td  align=left colspan="6"><edu:pageTag name="pageObject" property="queryResult"  scope="request"/></td>
</tr>
   <TR>
   <td width="9%"><a href="javascript:selectAll()">全选</a></td>
    <td colspan="3"> &nbsp;&nbsp; &nbsp;&nbsp;提交</td>
    <td align=center colspan=3><div align="left">   &nbsp;&nbsp;&nbsp;
   <A href="<%=request.getContextPath()%>/member/addelective.jsp">新增........</A></div></td>
   </TR>
</table>
<html:hidden property="pageNum"/>
</html:form></body>
</html>