jsp接收list值的问题

Question

我的java文件有这二句代码，想把collection里的值传到jsp页面上
　　　　Collection search_user_id=sqlCon.getUSER_ID(USER_NAME);
　　　　request.setAttribute("name",search_user_id);
jsp页面里
<%
String USER_ID=null;
List objList = (List)request.getAttribute("name");
request.setAttribute("objList",objList);
%>
把值取得我想把得到的值显示到页面上
　　　<display:table name="objList" export="true" requestURI="" pagesize="10" sort="list" class="its">
<display:caption>用户名:<%=request.getAttribute("USER_ID")%></display:caption>
　　　</display:table>
可是这样不能显示，会报错，请问一下，我应该怎么改

Answer 1

 <display:table name="objList" export="true" requestURI="" pagesize="10" sort="list" class="its"> 
<display:caption>用户名: <%=objList.get(0)%> </display:caption> 
　　　 </display:table> 

Answer 2

<%=request.getAttribute("USER_ID")%>
不对.你并没有设置过"USER_ID"的attribute
应该用你刚才取得的objList
objList.get(0)

Answer 3

<% 
String USER_ID=null; 
List objList = (List)request.getAttribute("name"); 
request.setAttribute("objList",objList); -这句不用，因为在同一个页面，直接用上面的objList 就可以取到
%> <display:table name="objList" export="true" requestURI="" pagesize="10" sort="list" class="its"> 
<display:caption>用户名: <%=request.getAttribute("USER_ID")%> </display:caption> 
　　　 </display:table>
上面红的代码应该改成 <%=objList.get(0)")%>如果只有一个，多个的话再外面用for(int i=0;i<objList.size();i++)
取的时候用<%=objList.get(i)")%>

Answer 4

唉，还是会报错哦　　zlm                             
2008-8-7 12:46:49 org.apache.catalina.core.ApplicationDispatcher invoke
严重: Servlet.service() for servlet jsp threw exception
java.lang.ClassNotFoundException: org.displaytag.tags.TableTagExtraInfo
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1358)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)
at org.apache.jasper.compiler.TagLibraryInfoImpl.createTagInfo(TagLibraryInfoImpl.java:416)
at org.apache.jasper.compiler.TagLibraryInfoImpl.parseTLD(TagLibraryInfoImpl.java:250)
at org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:163)
at org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:420)
at org.apache.jasper.compiler.Parser.parseDirective(Parser.java:476)
at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1426)
at org.apache.jasper.compiler.Parser.parse(Parser.java:133)
at org.apache.jasper.compiler.ParserController.doParse(ParserController.java:215)
at org.apache.jasper.compiler.ParserController.parse(ParserController.java:102)
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:167)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:306)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:286)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:273)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:566)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:308)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:687)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:469)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:403)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
at org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1085)
at org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:398)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:241)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:228)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:216)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:634)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)
at java.lang.Thread.run(Unknown Source)
2008-8-7 12:46:49 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet action threw exception
java.lang.ClassNotFoundException: org.displaytag.tags.TableTagExtraInfo
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1358)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)
at org.apache.jasper.compiler.TagLibraryInfoImpl.createTagInfo(TagLibraryInfoImpl.java:416)
at org.apache.jasper.compiler.TagLibraryInfoImpl.parseTLD(TagLibraryInfoImpl.java:250)
at org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:163)
at org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:420)
at org.apache.jasper.compiler.Parser.parseDirective(Parser.java:476)
at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1426)
at org.apache.jasper.compiler.Parser.parse(Parser.java:133)
at org.apache.jasper.compiler.ParserController.doParse(ParserController.java:215)
at org.apache.jasper.compiler.ParserController.parse(ParserController.java:102)
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:167)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:306)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:286)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:273)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:566)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:308)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:687)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:469)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:403)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
at org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1085)
at org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:398)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:241)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:228)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:216)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:634)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)
at java.lang.Thread.run(Unknown Source)
一开始的zlm是我要取得的数据，我把它打印出来了，想知道是不是从数据库里取得数据，可是既然有打印出来，说明已经被我放到list里了，可为什么页面上就是无法取得这个list里的值呢

Answer 5

<%=request.getAttribute("USER_ID")%>
============================
指的是从request里取值，你现在应该从objList 里面取值
至于怎么取，由于我不认识你的这个标签，没法告诉你了，自己去搜索下

Answer 6

有两个疑问：
1、你的sqlCon.getUSER_ID(USER_NAME)方法返回的是什么类型的值？
如果返回的是List的实现类那么没问题，如果不是，那么你下面的强制转换为List就有问题了。
2、你的<%=request.getAttribute("USER_ID")%>这句代码能执行吗？
从你给出的代码来看你并未将“USER_ID”存放到request中，所以你能取到USER_ID的值？

Answer 7

同意7楼的Collection search_user_id=sqlCon.getUSER_ID(USER_NAME); 
这个东西返回是个Collection 又不是结果集，也不是LIST，
你强行request.setAttribute("name",search_user_id); 这样操作，你在页面
List objList = (List)request.getAttribute("name"); 这样取得的又是什么。这是我的迭代显示
java.util.Vector v=pageCtl.getResult();
     java.util.Enumeration e = v.elements();
     while(e.hasMoreElements())
     {
     Object[] obj = (Object[])e.nextElement();
     
%>
<tr>
<td align="center" width="50%"><%=obj[0]%></td>
<td align="center" width="50%"><%=obj[1]%></td>
</tr><%}%>或者你后面ResultSet search_user_id=sqlCon.getUSER_ID(USER_NAME); 
　　　　request.setAttribute("name",search_user_id); 
前台强行转换成ResultSet rs = (ResultSet)request.getAttribute("name");  
while(rs.next())
{
    <%=rs.getString("ooxx")%>

Answer 8

其实不是值有没有传过来的问题,是display标签的使用问题