哥们们救我！！！javax.servlet.jsp.JspException: Cannot find bean a in any scope

<html>
<head>
<title>JSP for pageForm form</title>
</head>
<body>
        <logic:iterate id="a" name="arrayList" type="com.yourcompany.struts.action.PageMain">
            <tr>
              <td><bean:write name="a" property="psw"/></td>
              <td><bean:write name="a" property="name"/></td>
            </tr>
        </logic:iterate>
<html:link page="/index.do?action=nextPage">nextPage</html:link>
</body>
</html>

out.print(request.getAttribute("arrayList"))里面有东西，PageMain：

package com.yourcompany.struts.action;

public class PageMain
{
private String name="";
private String psw="";

public void setName(String name)
{
this.name=name;
}

public void setPsw(String psw)
{
this.psw=psw;
}

public String getName()
{
return name;
}

public String getPsw()
{
return psw;
}

public void PageMain(String name,String psw)
{
this.name=name;
this.psw=psw;
}
}

24 个解决方案

#1

com.yourcompany.struts.action.PageMain这个类不在你的类路径里(或者根本没有这个累) 检查下

#2

找不到你要的类，路径错了

#3

你连<html:form>都没有呀
<html:form action="your_action" >
<logic:iterate id="a" name="formbeanName" property="arrayList">
            <tr>
              <td><bean:write name="a" property="psw"/></td>
              <td><bean:write name="a" property="name"/></td>
            </tr>
  </logic:iterate>
</html:form>

#4

package com.yourcompany.struts.action;

public class PageMain
{
private String name="";
private String psw="";

public void setName(String name)
{
this.name=name;
}

public void setPsw(String psw)
{
this.psw=psw;
}

public String getName()
{
return name;
}

public String getPsw()
{
return psw;
}

public void PageMain(String name,String psw)
{
this.name=name;
this.psw=psw;
}
}
在这里，我将<td><bean:write name="a" property="psw"/></td>
<td><bean:write name="a" property="name"/></td>去掉，不报错，加上就报。

#5

你没指定到对应的action，那么它也找不到你对应的form。
当然就无法取出form里面的属性了。
解决的办法有 1：按Octer(米粒)所说，加form指定action。
2：先执行action（可通过URL链接），将你的form放入scope当中，比如request，session。

#6

PageMain这个类要继承ActionForm

#7

按照哥们们的说法做了，还是出现“javax.servlet.jsp.JspException: Cannot find bean a in any scope”
index.jsp:
<html:form action="/index">
<head>
<title>JSP for pageForm form</title>
</head>
<body>
        <logic:iterate id="a" name="arrayList" type="com.yourcompany.struts.action.PageMain">
            <tr>
              <td><bean:write name="a" property="psw"/></td>
              <td><bean:write name="a" property="name"/></td>
            </tr>
        </logic:iterate>
<html:link page="/index.do?action=nextPage">nextPage</html:link>
</body>
</html:form>

struts-config.xml:
<struts-config>
  <data-sources />

  <form-beans >
    <form-bean name="Form" type="com.yourcompany.struts.action.PageMain" />
  </form-beans>

  <global-exceptions />
  <global-forwards />
  <action-mappings >
    <action
      input="/index.jsp"
      path="/index"
      scope="request"
      name="Form"
      type="com.yourcompany.struts.action.PageAction">
<forward name="success" path="/index.jsp"/>
</action>
  </action-mappings>

PageMain.java
public class PageMain extends ActionForm

#8

再次强调：请确保你的PageMain是在request或者是session域当中。
要么是在action类的form当中赋值，要么是手动往request或者session中加。已经说的很明白了。
或者将action代码贴出来。

#9

PageMain不继承ActionForm,再写一个PageForm

class PageForm extends ActionForm {
List arrayList = new ArrayList();
get and set method;
}

struts-config.xml
<form-bean name="Form" type="com.yourcompany.struts.action.PageForm" />

jsp
<logic:iterate id="a" name="Form" property="arrayList ">

或者直接将arrayList 放到request或者session中

#10

你没有把arrayList 放到request或者session中，请确认一下。

#11

谢谢哥们们的批评，以前的错误没了，出现
java.lang.ClassCastException
com.yourcompany.struts.action.PageAction.execute(PageAction.java:32)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:484)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:507)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

PageAction.java:
package com.yourcompany.struts.action;

import java.util.ArrayList;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

import com.yourcompany.struts.form.PageForm;

public class PageAction extends Action {

public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {
PageForm pageForm = (PageForm) form;
// TODO Auto-generated method stub
String action;
action=request.getParameter("action");
//if(action=="nextPage")
//{
PageController pagecontroller=new PageController();
pagecontroller.Controller();
pagecontroller.intPage(action);
ArrayList arrayList = new ArrayList();
arrayList=pagecontroller.start();
//}
request.setAttribute("arrayList",arrayList);
//HttpServletRequest request=null;
//request.setAttribute("arrayList1","2");
return (mapping.findForward("success"));
}

}

#12

已经把我说糊渡了，我现在的arrayList里有值，out.print(request.getAttribute("arrayList"));可以输出，我想用STRUTS标签把值输出。
PageAction:
//Created by MyEclipse Struts
// XSL source (default): platform:/plugin/com.genuitec.eclipse.cross.easystruts.eclipse_4.0.1/xslt/JavaClass.xsl

package com.yourcompany.struts.action;

import java.util.ArrayList;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

import com.yourcompany.struts.form.PageForm;

public class PageAction extends Action {

public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {
//PageForm pageForm = (PageForm) form;
// TODO Auto-generated method stub
String action;
action=request.getParameter("action");
//if(action=="nextPage")
//{
PageController pagecontroller=new PageController();
pagecontroller.Controller();
pagecontroller.intPage(action);
ArrayList arrayList = new ArrayList();
arrayList=pagecontroller.start();
//}
request.setAttribute("arrayList",arrayList);
//HttpServletRequest request=null;
//request.setAttribute("arrayList1","2");
return (mapping.findForward("success"));
}

}

PageForm:
package com.yourcompany.struts.action;

import org.apache.struts.action.ActionForm;

public class PageForm extends ActionForm
{
private String name="";
private String psw="";

public void setName(String name)
{
this.name=name;
}

public void setPsw(String psw)
{
this.psw=psw;
}

public String getName()
{
return name;
}

public String getPsw()
{
return psw;
}

public void PageForm(String name,String psw)
{
this.name=name;
this.psw=psw;
}
}

#13

首先说一下，标签 logic:iterate 和 bean:write 跟标签 html:form 没有任何直接关联的，都可以单独使用。所以肯定不是这个问题。
－－－－－－－－－－－－－－－－－－－－－－－－－
楼主提到：
在这里，我将<td><bean:write name="a" property="psw"/></td>
<td><bean:write name="a" property="name"/></td>去掉，不报错，加上就报。
－－－－－－－－－－－－－－－－－－－－－－－－－
所以要重点检查你的arrayList里确实放的就是PageMain的实例。
能把你的out.print(request.getAttribute("arrayList"))输出贴出来吗？

#14

顶楼上的！不一定要用form

#15

出现ClassCastException，说明是类型转换错误，检查一下你的arraylist里面的到底是什么类型。

另外，你先不用iterate:logic，你先用
<%
List list=(List)request.getAttribute("arraylist");
%>
然后用Iterator依次读出，看结果是否对，同时顺便验证一下arraylist里的数据类型。如果对的话，然后再讨论标签的问题，否则，没有任何意义。

#16

ArrayList arr =(ArrayList)request.getAttribute("arrayList");
Iterator it= arr.iterator();
while(it.hasNext())
{

out.println(it.next().toString());

}
输出：
com.yourcompany.struts.action.PageForm@8a4156 com.yourcompany.struts.action.PageForm@c787d7 com.yourcompany.struts.action.PageForm@1a76e19 com.yourcompany.struts.action.PageForm@12d49e7 com.yourcompany.struts.action.PageForm@4f14b0 com.yourcompany.struts.action.PageForm@1d74bb1

#17

晕，这样打出的信息有什么用？(至少我看不懂？）
你应该把it.next()强制转换成PageMain 或者PageForm? 然后看看是否可以打出你要的name,psw；如果此转换过程出错，说明你arrayList里面存放的根本不是PageMain的对象，当然出现你所说的错误

#18

这说明你的arraylist里存的是pageform对象啊，你用
while(it.hasNext())
{
    PageForm pf=(PageForm)it.next();
    System.out.println(pf.getXX());
    ...
}
看看能否打印出结果来。
然后在看看，你标签里取的那个对象，到底是pageform还是pagemain.

#19

你的PageForm跟PageMain是什么关系啊？如果PageMain不是PageForm的父类，当然会出错了，从你打印出来的信息就可以很清楚判断的了。

#20

按照上面的的朋友我把PageMain改成了PageForm，现在没有PageMain了。我输出结果：
ArrayList arr =(ArrayList)request.getAttribute("arrayList");
Iterator it= arr.iterator();
com.yourcompany.struts.action.PageForm fm=null;
while(it.hasNext())
{
fm=(com.yourcompany.struts.action.PageForm)it.next();
}
又出现错误，我的request.getAttribute("arrayList")里面有值呀？！
java.lang.NullPointerException
com.yourcompany.struts.action.PageAction.execute(PageAction.java:39)
org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:484)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:274)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:507)
javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

//Created by MyEclipse Struts
// XSL source (default): platform:/plugin/com.genuitec.eclipse.cross.easystruts.eclipse_4.0.1/xslt/JavaClass.xsl

package com.yourcompany.struts.action;

import java.util.*;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

import com.yourcompany.struts.form.PageForm;

public class PageAction extends Action {

public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {
//PageForm pageForm = (PageForm) form;
// TODO Auto-generated method stub
String action;
action=request.getParameter("action");
//if(action=="nextPage")
//{
PageController pagecontroller=new PageController();
pagecontroller.Controller();
pagecontroller.intPage(action);
ArrayList arrayList = new ArrayList();
arrayList=pagecontroller.start();
//}
//request.setAttribute("arrayList",arrayList);
ArrayList arr =(ArrayList)request.getAttribute("arrayList");
Iterator it= arr.iterator();
com.yourcompany.struts.action.PageForm fm=null;
while(it.hasNext())
{
fm=(com.yourcompany.struts.action.PageForm)it.next();
//out.println(it.next());

}
//System.out.println(fm.getName());
request.setAttribute("a",fm.getName());
//HttpServletRequest request=null;
//request.setAttribute("arrayList1","2");
return (mapping.findForward("success"));
}

}

#21

晕倒，楼主还用ArrayList arr =(ArrayList)request.getAttribute("arrayList");这个在action中这么取值？？这样不是空指针才怪，恩，看来楼主得好好补补基础知识才行。把这个注释掉就成了，明显的程序基本错误哦。

#22

另外，把前一句注释打开

#23

的确应该好好补补了。

#24

解决了，STRUTS自动给我生成了一个PageForm,里面什么也没有。

#1