無狀態會話bean可以保護最終方法嗎？

Question

我已經定義了一個會話bean的基類。這個類是抽象的，包含受保護的最終方法。會話實現類擴展了抽象類並定義了其他方法。在部署期間，Glassfish 3.1.2服務器會生成一個異常，指出該方法被覆蓋。

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

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

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

在部署過程中，glassfish服務器拋出異常。如果我使AbstractSessionBean的方法非最終，則部署成功。

這是否意味着會話bean不能有最終方法？或者這種行爲僅限於Glassfish 3.1.2。

異常消息是：

[#|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

簡短的回答是「是」，但長期答案是「是一般，但不使用無界面視圖時」。爲無界面視圖的限制從EJB 3.2規範的3.4.4節來間接：

只有公共bean類和除 java.lang.Object中任何超類的方法可以通過沒有被調用接口視圖。 通過 嘗試調用任何其他訪問修飾符的方法時，無界面視圖引用必須導致 javax.ejb.EJBException。

當生成無界面視圖代理時，EJB容器必須創建EJB類的子類並覆蓋所有提供代理行爲的公共方法。但是，上述規範引用中的第二句暗示，爲了拋出無條件的EJBException，還必須重寫所有其餘的非私有方法。也就是說，來自應用程序服務器的錯誤消息可能會更好。