Hibernate一对多映射初始化集合失败

Question

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.qianqiu.dao.po.InsPerson.insEvents, no session or session was closed
at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380)
at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372)
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:365)
at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:108)
at org.hibernate.collection.PersistentSet.iterator(PersistentSet.java:186)
at org.apache.struts.taglib.logic.IterateTag.doStartTag(IterateTag.java:257)
at org.apache.jsp.showPerson_jsp._jspService(showPerson_jsp.java:299)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:68)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:376)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:674)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:462)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:401)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:329)
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.doGet(ActionServlet.java:414)
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:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:201)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:163)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:108)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:556)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:401)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:242)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:267)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:245)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:260)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
2010-11-15 21:49:51 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet [action] in context with path [/QianQiu] threw exception [An exception occurred processing JSP page /showPerson.jsp at line 80<logic:iterate id="person" name="personList" scope="request"
offset="<%=start%>" length="9">
<td width="85">
<a href="showInfo.do?id=${person.id }"><img src="${person.bioimage }" width="85" height="110" border="0"></img></a>
<div align="center">
<a href="showInfo.do?id=${person.id }">${person.name }</a>
</div>
<div>
<logic:equal value="event" parameter="page">
<bean:define id="events" name="person" property="insEvents"></bean:define>
<!-- 第80行 --><logic:iterate id="event" name="events">
${event.description }
</logic:iterate>
</logic:equal>
</div>
</td>
</logic:iterate>不明白为什么这出异常了，它说我的集合不对，我的InsPerson.java和InsEvent.java是一对多的关系，关系都已经映射好了，在第79行我把person对象中的insEvents赋给events，这个集合存的是InsEvent类的对象，然后遍历这个集合，取出description属性，但是在这就出错了，不知道哪里出了问题问题！

Answer 1

那错误是因为你在session关闭后还去访问数据库.一般在级联查询时最容易出现这个问题.
级联查询,不会查出所关联的对象的所有内容,而是只查出ID.所以你访问级联对象的ID时没问题,但
如果你访问其他属性,因为之前没有查出来,所以会再次根据ID去访问数据库,而session已经关闭,所以
会有那样的错.你要在hibernate配置文件中配置延迟加载,具体可以看下hibernate
的加载策略.

Answer 2

failed to lazily initialize a collection of role: com.qianqiu.dao.po.InsPerson.insEvents, no session or session was closed
session 关闭了 。

Answer 3

hibernateSessionView 让session信息显示完成之后再关闭

Answer 4

无论是hibernateSessionView还是修改加载策略.
性能都不怎么好控制,建议还是要用的哪些属性,用左右连接查询的好.

Answer 5

1,2,detachedCriteria dc=detachedCriteria .forClass(xx.class);
dc.setFeachMode("accs",fetchmode.join);

Answer 6

lazy=false或者如果你现在用到了Spring可以配置Spring的一个过滤器OpenSessionInView

Answer 7

问题已解决，第一种方案是不去关闭Session，不过这个方法行不通，运行一会就内存溢出了，第二种方案是在一那面设置lazy=false，但是谁能告诉我hibernateSessionView是什么意思！

Answer 8

看错误信息就知道了，，，把Lazy设为false，就ok啦。。