是否可以将@EJB作为泛型类型？

-1

import javax.ejb.EJB; 

public abstract class AbstractController<TEJB extends EntityEJB<TENTITY>, TENTITY extends EntityInterface> { 
    @EJB 
    protected TEJB ejb; 
    ... 

import javax.enterprise.context.SessionScoped; 
import javax.faces.bean.ManagedBean; 

@ManagedBean 
@SessionScoped 
public class UserController extends AbstractController<UserEJB, User> { 
    ... 

import javax.ejb.Stateless; 

@Stateless 
public abstract class EntityEJB<T extends EntityInterface> { 
    ... 

import javax.ejb.Stateless; 

@Stateless 
public class UserEJB extends EntityEJB<User> { 
    ...

它编译，部署，但每当代码进入一些EJB方法，它抛出：是否可以将@EJB作为泛型类型？

[#|2011-02-14T12:36:20.531+0100|WARNING|glassfish3.0.1|javax.enterprise.system.container.ejb.com.sun.ejb.containers|_ThreadID=25;_ThreadName=Thread-1;|A system exception occurred during an invocation on EJB EntityEJB method public int ejb.EntityEJB.getItemCount() 
javax.ejb.EJBException: javax.ejb.EJBException: javax.ejb.CreateException: Could not create stateless EJB 
    at com.sun.ejb.containers.StatelessSessionContainer._getContext(StatelessSessionContainer.java:448) 
    at com.sun.ejb.containers.BaseContainer.getContext(BaseContainer.java:2467) 
    at com.sun.ejb.containers.BaseContainer.preInvoke(BaseContainer.java:1860) 
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:188) 
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:84) 
    at $Proxy150.getItemCount(Unknown Source) 
    at ejb.__EJB31_Generated__EntityEJB__Intf____Bean__.getItemCount(Unknown Source) 
    at controller.AbstractController.getItemCount(AbstractController.java:88) 
    at controller.AbstractController.getPagingInfo(AbstractController.java:29) 
    at controller.AbstractController.getItems(AbstractController.java:40) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
    at java.lang.reflect.Method.invoke(Method.java:597) 
    at javax.el.BeanELResolver.getValue(BeanELResolver.java:302) 
    at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:175) 
    at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72) 
    at com.sun.el.parser.AstValue.getValue(AstValue.java:116) 
    at com.sun.el.parser.AstValue.getValue(AstValue.java:163) 
    at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:219) 
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:102) 
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:190) 
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:178) 
    at javax.faces.component.UIData.getValue(UIData.java:554) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
    at java.lang.reflect.Method.invoke(Method.java:597) 
    at com.sun.faces.facelets.util.DevTools.writeAttributes(DevTools.java:368) 
    at com.sun.faces.facelets.util.DevTools.writeStart(DevTools.java:417) 
    at com.sun.faces.facelets.util.DevTools.writeComponent(DevTools.java:238) 
    at com.sun.faces.facelets.util.DevTools.writeComponent(DevTools.java:257) 
    at com.sun.faces.facelets.util.DevTools.writeComponent(DevTools.java:257) 
    at com.sun.faces.facelets.util.DevTools.writeComponent(DevTools.java:257) 
    at com.sun.faces.facelets.util.DevTools.writeComponent(DevTools.java:257) 
    at com.sun.faces.facelets.util.DevTools.writeComponent(DevTools.java:257) 
    at com.sun.faces.facelets.util.DevTools.debugHtml(DevTools.java:121) 
    at com.sun.faces.renderkit.RenderKitUtils.renderHtmlErrorPage(RenderKitUtils.java:1139) 
    at com.sun.faces.context.ExceptionHandlerImpl.throwIt(ExceptionHandlerImpl.java:249) 
    at com.sun.faces.context.ExceptionHandlerImpl.handle(ExceptionHandlerImpl.java:136) 
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:119) 
    at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) 
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:313) 
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188) 
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641) 
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97) 
    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185) 
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:325) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:226) 
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165) 
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791) 
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693) 
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954) 
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170) 
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135) 
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102) 
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88) 
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76) 
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53) 
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57) 
    at com.sun.grizzly.ContextTask.run(ContextTask.java:69) 
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330) 
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309) 
    at java.lang.Thread.run(Thread.java:619) 
Caused by: javax.ejb.EJBException: javax.ejb.CreateException: Could not create stateless EJB 
    at com.sun.ejb.containers.StatelessSessionContainer$SessionContextFactory.create(StatelessSessionContainer.java:720) 
    at com.sun.ejb.containers.util.pool.NonBlockingPool.getObject(NonBlockingPool.java:200) 
    at com.sun.ejb.containers.StatelessSessionContainer._getContext(StatelessSessionContainer.java:443) 
    ... 66 more 
Caused by: javax.ejb.CreateException: Could not create stateless EJB 
    at com.sun.ejb.containers.StatelessSessionContainer.createStatelessEJB(StatelessSessionContainer.java:528) 
    at com.sun.ejb.containers.StatelessSessionContainer.access$000(StatelessSessionContainer.java:90) 
    at com.sun.ejb.containers.StatelessSessionContainer$SessionContextFactory.create(StatelessSessionContainer.java:718) 
    ... 68 more 
Caused by: java.lang.InstantiationException 
    at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:30) 
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513) 
    at java.lang.Class.newInstance0(Class.java:355) 
    at java.lang.Class.newInstance(Class.java:308) 
    at com.sun.ejb.containers.BaseContainer._constructEJBInstance(BaseContainer.java:1640) 
    at com.sun.ejb.containers.BaseContainer.createEjbInstanceAndContext(BaseContainer.java:1623) 
    at com.sun.ejb.containers.StatelessSessionContainer.createStatelessEJB(StatelessSessionContainer.java:469) 
    ... 70 more

如果我改变从通用型到具体的类（UserEJB）EJB，它工作得很好。对不起，如果这是初学者的问题，我只是从Java开始......

Bozho指出，抽象类不应该用@Stateless注释。这是有道理的，但它似乎更早崩溃 - 因为它找不到名为“EntityEJB”的EJB。好吧，在前一种情况下，依赖注入器似乎试图注入EntityEJB的实例（这是泛型TEJB的超类），它是抽象类，不能被实例化（因此不能被注入），这会导致异常“无法创建无状态的EJB”。整个堆栈跟踪wihtout @Stateless：

com.sun.faces.mgbean.ManagedBeanCreationException: An error occurred performing resource injection on managed bean groupController 
    at com.sun.faces.mgbean.BeanBuilder.injectResources(BeanBuilder.java:211) 
    at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:103) 
    at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:405) 
    at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:267) 
    at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:86) 
    at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:175) 
    at com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:72) 
    at com.sun.el.parser.AstIdentifier.getValue(AstIdentifier.java:99) 
    at com.sun.el.parser.AstValue.getValue(AstValue.java:158) 
    at com.sun.el.parser.AstPlus.getValue(AstPlus.java:55) 
    at com.sun.el.parser.AstDeferredExpression.getValue(AstDeferredExpression.java:59) 
    at com.sun.el.parser.AstCompositeExpression.getValue(AstCompositeExpression.java:64) 
    at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:219) 
    at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:102) 
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:190) 
    at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:178) 
    at javax.faces.component.UIOutput.getValue(UIOutput.java:168) 
    at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getValue(HtmlBasicInputRenderer.java:205) 
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.getCurrentValue(HtmlBasicRenderer.java:338) 
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeEnd(HtmlBasicRenderer.java:164) 
    at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:878) 
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1620) 
    at javax.faces.render.Renderer.encodeChildren(Renderer.java:168) 
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:848) 
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:287) 
    at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:106) 
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:848) 
    at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:287) 
    at com.sun.faces.renderkit.html_basic.GridRenderer.renderRow(GridRenderer.java:185) 
    at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:129) 
    at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:848) 
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1613) 
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) 
    at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1616) 
    at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:380) 
    at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:126) 
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:127) 
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) 
    at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) 
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:313) 
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188) 
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641) 
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97) 
    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185) 
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:325) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:226) 
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165) 
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791) 
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693) 
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954) 
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170) 
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135) 
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102) 
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88) 
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76) 
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53) 
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57) 
    at com.sun.grizzly.ContextTask.run(ContextTask.java:69) 
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330) 
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309) 
    at java.lang.Thread.run(Thread.java:619) 
Caused by: com.sun.faces.spi.InjectionProviderException: com.sun.enterprise.container.common.spi.util.InjectionException: Exception attempting to inject Remote ejb-ref name=controller.AbstractController/ejb,Remote 3.x interface =ejb.EntityEJB,ejb-link=null,lookup=null,mappedName=,jndi-name=ejb.EntityEJB,refType=Session into class controller.AbstractController 
    at org.glassfish.faces.integration.GlassFishInjectionProvider.inject(GlassFishInjectionProvider.java:98) 
    at com.sun.faces.mgbean.BeanBuilder.injectResources(BeanBuilder.java:205) 
    ... 63 more 
Caused by: com.sun.enterprise.container.common.spi.util.InjectionException: Exception attempting to inject Remote ejb-ref name=controller.AbstractController/ejb,Remote 3.x interface =ejb.EntityEJB,ejb-link=null,lookup=null,mappedName=,jndi-name=ejb.EntityEJB,refType=Session into class controller.AbstractController 
    at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl._inject(InjectionManagerImpl.java:614) 
    at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl.inject(InjectionManagerImpl.java:384) 
    at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl.injectInstance(InjectionManagerImpl.java:168) 
    at org.glassfish.faces.integration.GlassFishInjectionProvider.inject(GlassFishInjectionProvider.java:94) 
    ... 64 more 
Caused by: javax.naming.NamingException: Lookup failed for 'java:comp/env/controller.AbstractController/ejb' in SerialContext [Root exception is javax.naming.NamingException: Exception resolving Ejb for 'Remote ejb-ref name=controller.AbstractController/ejb,Remote 3.x interface =ejb.EntityEJB,ejb-link=null,lookup=null,mappedName=,jndi-name=ejb.EntityEJB,refType=Session' . Actual (possibly internal) Remote JNDI name used for lookup is 'ejb.EntityEJB#ejb.EntityEJB' [Root exception is javax.naming.NamingException: Lookup failed for 'ejb.EntityEJB#ejb.EntityEJB' in SerialContext [Root exception is javax.naming.NameNotFoundException: ejb.EntityEJB#ejb.EntityEJB not found]]] 
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:442) 
    at javax.naming.InitialContext.lookup(InitialContext.java:392) 
    at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl._inject(InjectionManagerImpl.java:513) 
    ... 67 more 
Caused by: javax.naming.NamingException: Exception resolving Ejb for 'Remote ejb-ref name=controller.AbstractController/ejb,Remote 3.x interface =ejb.EntityEJB,ejb-link=null,lookup=null,mappedName=,jndi-name=ejb.EntityEJB,refType=Session' . Actual (possibly internal) Remote JNDI name used for lookup is 'ejb.EntityEJB#ejb.EntityEJB' [Root exception is javax.naming.NamingException: Lookup failed for 'ejb.EntityEJB#ejb.EntityEJB' in SerialContext [Root exception is javax.naming.NameNotFoundException: ejb.EntityEJB#ejb.EntityEJB not found]] 
    at com.sun.ejb.EjbNamingReferenceManagerImpl.resolveEjbReference(EjbNamingReferenceManagerImpl.java:174) 
    at com.sun.enterprise.container.common.impl.ComponentEnvManagerImpl$EjbReferenceProxy.create(ComponentEnvManagerImpl.java:1040) 
    at com.sun.enterprise.naming.impl.GlassfishNamingManagerImpl.lookup(GlassfishNamingManagerImpl.java:688) 
    at com.sun.enterprise.naming.impl.GlassfishNamingManagerImpl.lookup(GlassfishNamingManagerImpl.java:657) 
    at com.sun.enterprise.naming.impl.JavaURLContext.lookup(JavaURLContext.java:148) 
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:428) 
    ... 69 more 
Caused by: javax.naming.NamingException: Lookup failed for 'ejb.EntityEJB#ejb.EntityEJB' in SerialContext [Root exception is javax.naming.NameNotFoundException: ejb.EntityEJB#ejb.EntityEJB not found] 
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:442) 
    at javax.naming.InitialContext.lookup(InitialContext.java:392) 
    at com.sun.ejb.EjbNamingReferenceManagerImpl.resolveEjbReference(EjbNamingReferenceManagerImpl.java:169) 
    ... 74 more 
Caused by: javax.naming.NameNotFoundException: ejb.EntityEJB#ejb.EntityEJB not found 
    at com.sun.enterprise.naming.impl.TransientContext.doLookup(TransientContext.java:197) 
    at com.sun.enterprise.naming.impl.TransientContext.lookup(TransientContext.java:168) 
    at com.sun.enterprise.naming.impl.SerialContextProviderImpl.lookup(SerialContextProviderImpl.java:58) 
    at com.sun.enterprise.naming.impl.LocalSerialContextProviderImpl.lookup(LocalSerialContextProviderImpl.java:101) 
    at com.sun.enterprise.naming.impl.SerialContext.lookup(SerialContext.java:430) 
    ... 76 more

来源

2011-02-14 Tomik

@EJB是一个注释，用于将其注入您的课堂。您不能使用泛型类对其进行注释，否则Container将无法找到该字段中应使用的实例。

来源

2011-02-14 14:55:58

从异常堆栈跟踪我会假设你没有一个无参数的构造函数。确保你有一个，然后再试一次。泛型应该有一个问题。

此外，您不应该能够使抽象类成为无状态bean。所以从这里删除注释：

@Stateless 
public abstract class EntityEJB

顺便说一句，你正试图注入..注释？您应该使用@EJB注释一个真正的无状态bean接口。

来源

2011-02-14 11:59:35 Bozho

感谢您的回答，但这不是问题 - 两个类（AbstractController和UserController）都没有参数的公共构造函数。 – Tomik 2011-02-14 13:32:46

@Tomik你能在课堂上展示所有的注解吗？ – Bozho 2011-02-14 13:37:03

是的，这是可能的。它编译并工作（如果你正在使用一个坚实的EE应用程序容器，如wildfly或weblogic）。

在实现接口定义的bean上使用implements（用例如@Local注释）。在抽象类中，你可以实现所有的bean实现中共享的方法。不要将@Override注释放在任何这些方法上。

来源

2015-07-23 13:07:12 feder

是否可以将@EJB作为泛型类型？

回答

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