无状态会话bean可以保护final方法吗？

Question

我定义了一个会话bean基类。这个类是抽象的，包含受保护的最终方法。一个会话实现类扩展了抽象类并定义了额外的方法。在部署期间，Glassfish 3.1.2服务器生成一个异常，说明该方法被覆盖。

abstract class AbstractSessionBean {
    @PersistenceContext(unitName="primary")
    private EntityManager em;

    protected final EntityManager getEntityManager() {
       return em;
    }
}

@Startup
@Stateless
class RegistrationSessionBean extends AbstractSessionBean {
     public void loadRegistration() {
        ...
     }
}

在部署期间，glassfish服务器会抛出一个异常。如果我将AbstractSessionBean的方法设置为非final，那么部署就成功了。

这是否意味着会话bean不能有最终的方法？或者这种行为只针对Glassfish 3.1.2。

异常消息是：

[#|2013-08-26T17:45:48.542+0530|SEVERE|glassfish3.1.2|javax.enterprise.system.tools.admin.org.glassfish.deployment.admin|_ThreadID=47;_ThreadName=Thread-2;|Exception while loading the app : EJB Container initialization error
java.lang.RuntimeException: Could not invoke defineClass!
    at com.sun.ejb.containers.EjbOptionalIntfGenerator.makeClass(EjbOptionalIntfGenerator.java:448)
    at com.sun.ejb.containers.EjbOptionalIntfGenerator.access$200(EjbOptionalIntfGenerator.java:64)
    at com.sun.ejb.containers.EjbOptionalIntfGenerator$1.run(EjbOptionalIntfGenerator.java:99)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.ejb.containers.EjbOptionalIntfGenerator.loadClass(EjbOptionalIntfGenerator.java:96)
    at com.sun.ejb.containers.BaseContainer.instantiateOptionalEJBLocalBusinessObjectImpl(BaseContainer.java:3886)
    at com.sun.ejb.containers.StatelessSessionContainer.initializeHome(StatelessSessionContainer.java:253)
    at com.sun.ejb.containers.ContainerFactoryImpl.createContainer(ContainerFactoryImpl.java:167)
    at org.glassfish.ejb.startup.EjbApplication.loadContainers(EjbApplication.java:230)
    at org.glassfish.ejb.startup.EjbDeployer.load(EjbDeployer.java:305)
    at org.glassfish.ejb.startup.EjbDeployer.load(EjbDeployer.java:108)
    at org.glassfish.internal.data.ModuleInfo.load(ModuleInfo.java:186)
    at org.glassfish.internal.data.ApplicationInfo.load(ApplicationInfo.java:264)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:460)
    at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:240)
    at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:389)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$1.execute(CommandRunnerImpl.java:348)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:363)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1085)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1200(CommandRunnerImpl.java:95)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1291)
    at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1259)
    at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:461)
    at com.sun.enterprise.v3.admin.AdminAdapter.service(AdminAdapter.java:212)
    at com.sun.grizzly.tcp.http11.GrizzlyAdapter.service(GrizzlyAdapter.java:179)
    at com.sun.enterprise.v3.server.HK2Dispatcher.dispath(HK2Dispatcher.java:117)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$Hk2DispatcherCallable.call(ContainerMapper.java:354)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
    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:724)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.GeneratedMethodAccessor50.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.sun.ejb.containers.EjbOptionalIntfGenerator.makeClass(EjbOptionalIntfGenerator.java:445)
    ... 41 more
Caused by: java.lang.VerifyError: class org.bean.test.persistence.util.__EJB31_Generated__RegistrationSessionBean__Intf____Bean__ overrides final method getContext.()Ljavax/ejb/SessionContext;
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:792)
    ... 45 more
|#]

Answer 1

简短的答案是“是”，但长答案是“一般情况下是，但使用无接口视图时否”。无接口视图的限制间接来自EJB 3.2规范的第3.4.4节：

只有bean类和除java之外的任何超类的公共方法。对象可以通过无接口视图调用。试图通过无接口视图引用使用任何其他访问修饰符调用方法必须导致javax。ejb。EJBException。

生成无接口视图代理时，EJB容器必须创建EJB类的子类，并重写所有公共方法以提供代理行为。然而，上面引用的规范中的第二句话意味着，为了抛出无条件EJBException，还必须重写所有剩余的非私有方法。也就是说，来自应用服务器的错误消息可能会更好。