EJB3中@PersistenceContext具体是如何注入EntityManager的？

zdxym 2008-05-26 12:17:59

目前正在做一个javaAPP，里面使用到EJB3，我在按EJB3那本书上的要求配置好后，运行程序时出现找不到EntityManager的异常，我觉得应该是我的persistence.xml的配置问题，
<persistence-unit name="chmPersistence">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<jta-data-source>java:/MySqlDS</jta-data-source>
<properties>
<property name="hibernate.dialect"
value="org.hibernate.dialect.MySQL5Dialect" />
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.cache.provider_class"
value="org.hibernate.cache.HashtableCacheProvider" />
</properties>
</persistence-unit>

源代码里：
@PersistenceContext
private EntityManager em ;

异常：
11:03:29,359 ERROR [STDERR] java.lang.NullPointerException
11:03:29,359 ERROR [STDERR] at net.chm.DAO.D_workerDAOImpl.get(D_workerDAOImpl.java:34)
11:03:29,359 ERROR [STDERR] at net.chm.DAO.D_workerDAOImpl.getByName(D_workerDAOImpl.java:52)
11:03:29,359 ERROR [STDERR] at net.chm.bean.LoginActionBean.login(LoginActionBean.java:23)
11:03:29,359 ERROR [STDERR] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
11:03:29,359 ERROR [STDERR] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
11:03:29,359 ERROR [STDERR] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
11:03:29,359 ERROR [STDERR] at java.lang.reflect.Method.invoke(Method.java:585)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:112)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.interceptor.InvocationContextImpl.proceed(InvocationContextImpl.java:166)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.interceptor.EJB3InterceptorsInterceptor.invoke(EJB3InterceptorsInterceptor.java:63)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.entity.TransactionScopedEntityManagerInterceptor.invoke(TransactionScopedEntityManagerInterceptor.java:54)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.AllowedOperationsInterceptor.invoke(AllowedOperationsInterceptor.java:47)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:79)
11:03:29,359 ERROR [STDERR] at org.jboss.aspects.tx.TxInterceptor$Required.invoke(TxInterceptor.java:191)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInterceptor.java:95)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.stateless.StatelessInstanceInterceptor.invoke(StatelessInstanceInterceptor.java:62)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.aspects.security.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:77)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.security.Ejb3AuthenticationInterceptor.invoke(Ejb3AuthenticationInterceptor.java:110)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:46)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(AsynchronousInterceptor.java:106)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
11:03:29,359 ERROR [STDERR] at org.jboss.ejb3.stateless.StatelessContainer.dynamicInvoke(StatelessContainer.java:304)
11:03:29,359 ERROR [STDERR] at org.jboss.aop.Dispatcher.invoke(Dispatcher.java:106)
11:03:29,359 ERROR [STDERR] at org.jboss.aspects.remoting.AOPRemotingInvocationHandler.invoke(AOPRemotingInvocationHandler.java:82)
11:03:29,359 ERROR [STDERR] at org.jboss.remoting.ServerInvoker.invoke(ServerInvoker.java:769)
11:03:29,359 ERROR [STDERR] at org.jboss.remoting.transport.socket.ServerThread.processInvocation(ServerThread.java:573)
11:03:29,359 ERROR [STDERR] at org.jboss.remoting.transport.socket.ServerThread.dorun(ServerThread.java:373)
11:03:29,359 ERROR [STDERR] at org.jboss.remoting.transport.socket.ServerThread.run(ServerThread.java:166)
请朋友帮我想想是什么地方出现的问题，谢谢！

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