サーブレットがオブジェクト（コレクション）を渡すjspがあります。オブジェクトはセッション属性になります。
session.setAttribute("groupList", request.getAttribute("groups"));
タグを使用して、このコレクションのコンテンツからメニューを再帰的に生成します。
<c:forEach items="${groupList}" var="emp" begin="0" end="10">
<tag:menuRenderer groupList="${groupList}" />
</c:forEach>
内のこれらのアイテムは、クラスのオブジェクトですGroup。このクラスには、サブグループsubGroupsのリストと、と呼ばれる別のクラスのオブジェクトのリストが含まれていstudentsます。
私の問題は、タグ内のこの学生のリストにアクセスできないことです。これはタグコードです：
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib tagdir="/WEB-INF/tags" prefix="tag"%>
<%@ taglib uri='http://java.sun.com/jsp/jstl/functions' prefix='fn' %>
<%@ attribute name="groupList" type="java.util.Collection"%>
<c:forEach var="item" items="${groupList}">
<li><c:out value="${item.name}" /></li>
<br>
<!-- ##### here #### -->
<li><c:out value="${fn:length(item.students)}" /> <!-- #### doesn't work ####-->
<li><c:out value="${fn:length(item.subGroups)}" /> <!-- #### works #### -->
<ul>
<tag:menuRenderer groupList="${item.subGroups}" />
</ul>
</c:forEach>
を呼び出すとitem.students例外が発生しますが、strackトレースはjspで例外がスローされた場所のみを示しているため、正確にはわかりません。
SEVERE: Servlet.service() for servlet jsp threw exception
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:186)
at org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:137)
at org.hibernate.collection.internal.PersistentSet.size(PersistentSet.java:156)
at org.apache.taglibs.standard.functions.Functions.length(Functions.java:202)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.el.parser.AstFunction.getValue(AstFunction.java:112)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:185)
at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:986)
at org.apache.jsp.tag.webmenuRenderer_tag._jspx_meth_c_005fout_005f1(webmenuRenderer_tag.java:202)
at org.apache.jsp.tag.webmenuRenderer_tag._jspx_meth_c_005fforEach_005f0(webmenuRenderer_tag.java:143)
at org.apache.jsp.tag.webmenuRenderer_tag.doTag(webmenuRenderer_tag.java:97)
at org.apache.jsp.tag.webmenuRenderer_tag._jspx_meth_tag_005fmenuRenderer_005f0(webmenuRenderer_tag.java:240)
at org.apache.jsp.tag.webmenuRenderer_tag._jspx_meth_c_005fforEach_005f0(webmenuRenderer_tag.java:153)
at org.apache.jsp.tag.webmenuRenderer_tag.doTag(webmenuRenderer_tag.java:97)
at org.apache.jsp.testMenu2_jsp._jspx_meth_tag_005fmenuRenderer_005f0(testMenu2_jsp.java:173)
at org.apache.jsp.testMenu2_jsp._jspx_meth_c_005fforEach_005f0(testMenu2_jsp.java:138)
at org.apache.jsp.testMenu2_jsp._jspService(testMenu2_jsp.java:90)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:412)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:339)
at myPackage.controller.ControllerServlet.doGet(ControllerServlet.java:38)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Nov 29, 2012 5:50:36 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [Hello] in context with path [/HibernateTest] threw exception [An exception occurred processing JSP page /testMenu2.jsp at line 19
16:
17: <ul>
18: <c:forEach items="${treeMap}" var="emp" begin="0" end="10">
19: <tag:menuRenderer treeMap="${treeMap}" />
20: </c:forEach>
21: </ul>
22:
Stacktrace:] with root cause
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:186)
at org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:137)
at org.hibernate.collection.internal.PersistentSet.size(PersistentSet.java:156)
at org.apache.taglibs.standard.functions.Functions.length(Functions.java:202)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.el.parser.AstFunction.getValue(AstFunction.java:112)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:185)
at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:986)
at org.apache.jsp.tag.webmenuRenderer_tag._jspx_meth_c_005fout_005f1(webmenuRenderer_tag.java:202)
at org.apache.jsp.tag.webmenuRenderer_tag._jspx_meth_c_005fforEach_005f0(webmenuRenderer_tag.java:143)
at org.apache.jsp.tag.webmenuRenderer_tag.doTag(webmenuRenderer_tag.java:97)
at org.apache.jsp.tag.webmenuRenderer_tag._jspx_meth_tag_005fmenuRenderer_005f0(webmenuRenderer_tag.java:240)
at org.apache.jsp.tag.webmenuRenderer_tag._jspx_meth_c_005fforEach_005f0(webmenuRenderer_tag.java:153)
at org.apache.jsp.tag.webmenuRenderer_tag.doTag(webmenuRenderer_tag.java:97)
at org.apache.jsp.testMenu2_jsp._jspx_meth_tag_005fmenuRenderer_005f0(testMenu2_jsp.java:173)
at org.apache.jsp.testMenu2_jsp._jspx_meth_c_005fforEach_005f0(testMenu2_jsp.java:138)
at org.apache.jsp.testMenu2_jsp._jspService(testMenu2_jsp.java:90)
// and so on
なぜこれがうまくいかないのか誰かに教えてもらえたらとても嬉しいです！何かをインポートする必要がありますか？
前もって感謝します！:)