只有在 Netbeans 7.1 和 GlassFish Server 3.1 上编译代码后，EntityManager 才会出现异常答案

【问题标题】：Exception on EntityManager only after compiling code on Netbeans 7.1 and GlassFish Server 3.1只有在 Netbeans 7.1 和 GlassFish Server 3.1 上编译代码后，EntityManager 才会出现异常
【发布时间】：2012-02-29 16:06:30
【问题描述】：

我正在使用 Netbeans 7.1 和 GlassFish server 3.1 来部署我的第一个 Java EE 项目。自项目开始以来，我遇到了一个困扰我的问题，代码只是抛出了下面的异常（主要的也是最奇怪的 - java.lang.ClassCastException: com.bestdeal.entity.Games 不能强制转换com.bestdeal.entity.Games），在我对 ejb 代码进行任何更改/编译之后。当我重新启动 glassfish 服务器时，问题似乎总是得到解决，但如果我对代码进行任何更改，同样的问题会再次出现。

我在需要时使用 JPA、EntityManager 和 EntityManagerFactory 来构造 EntityManager。在我通过 faces 页面发出请求后访问数据库，然后调用 Managed Bean 中的一个函数，该函数反过来触发 EBJ 代码中的数据访问类请求（我在下面显示）。

有什么想法会导致这个烦人的问题吗？

javax.ejb.EJBException

javax.faces.el.EvaluationException: javax.ejb.EJBException
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
    at javax.faces.component.UICommand.broadcast(UICommand.java:315)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1539)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:98)
    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:91)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:162)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:330)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:174)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:828)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:725)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1019)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:722)
Caused by: javax.ejb.EJBException
    at com.sun.ejb.containers.BaseContainer.processSystemException(BaseContainer.java:5193)
    at com.sun.ejb.containers.BaseContainer.completeNewTx(BaseContainer.java:5091)
    at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:4879)
    at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:2039)
    at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:1990)
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:222)
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:88)
    at $Proxy219.prepareSession(Unknown Source)
    at com.bestdeal.ejb.__EJB31_Generated__BestDeal__Intf____Bean__.prepareSession(Unknown Source)
    at com.bestdeal.web.BestDealMBean.prepareSession(BestDealMBean.java:29)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at javax.el.BeanELResolver.invokeMethod(BeanELResolver.java:737)
    at javax.el.BeanELResolver.invoke(BeanELResolver.java:467)
    at javax.el.CompositeELResolver.invoke(CompositeELResolver.java:254)
    at com.sun.el.parser.AstValue.invoke(AstValue.java:228)
    at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:297)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
    ... 33 more
Caused by: java.lang.ClassCastException: com.bestdeal.entity.Games cannot be cast to com.bestdeal.entity.Games
    at com.bestdeal.ejb.DataAccess.GetSessionInit(DataAccess.java:263)
    at com.bestdeal.ejb.EventProcessor.StartEventProcessor(EventProcessor.java:65)
    at com.bestdeal.ejb.BestDeal.prepareSession(BestDeal.java:75)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052)
    at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124)
    at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5366)
    at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:619)
    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
    at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571)
    at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162)
    at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:144)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861)
    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
    at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:370)
    at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:5338)
    at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5326)
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:214)
    ... 47 more

EJB 代码：

public class DataAccess {
    private final EntityManagerFactory emf;
    private EntityManager em;
    public DataAccess() {
        emf = Persistence.createEntityManagerFactory("Best-ejbPU");
        em = emf.createEntityManager();
    }

    public Games GetSessionInit(int SessionId){

        em.clear();
        Query query = em.createNativeQuery("update games set PeopleInStore=MarketShare*MarketTotal where gameindex=1;");
        query.executeUpdate();


        Query querysql = em.createQuery("select g from Games g where g.sessionNumber=" + SessionId);
        List<Games> l = querysql.getResultList();
        return l.get(0);//=>javax.ejb.EJBException occurs here !!!!!!!!!!!!!!!!!!
    }
}

【问题讨论】：

相关问题：Servlet Exception + Class Cast Exception + Glassfish + ...
还有：stackoverflow.com/questions/2614989/…

标签： jakarta-ee persistence glassfish-3 netbeans-7

【解决方案1】：

这在一定程度上取决于您如何设置持久性单元，但我对这不起作用并不感到惊讶。

您用来获取实体管理器的方法是Java SE 方法。这在 Java EE 中不一定支持。我确信同样的代码也不会在 JBoss AS 上运行。

除非您跳过注释，否则您显示的 bean 也不是 EJB（因此，您显示的不是 EJB 代码）。

在 Java EE 中，您应该注入实体管理器，或者从 JNDI 中查找它。然后你的 bean 看起来像这样：

@Stateless
public class DataAccess {

    @PersistenceContext    
    private EntityManager em;

    public Games getSessionInit(int SessionId) {            
        em.createNativeQuery("update games set PeopleInStore = MarketShare * MarketTotal where gameindex = 1;")
          .executeUpdate();

        return em.createQuery("select g from Games g where g.sessionNumber=" + SessionId)
                 .getResultList()
                 .get(0);
    }
}

（与问题无关，但您可能希望重构代码不要盲目地获取第一个元素；该列表可能为空。另外考虑使用命名查询机制将您的查询放入单独的文件中，参见例如Where to put named queries in JPA)

【讨论】：