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，部署但是只要代码进入某个EJB方法，它就抛出：
[#|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
如果我将EJB从泛型类型更改为具体类（UserEJB），则效果很好。如果这是初学者的问题，我很抱歉，我刚开始使用Java ...
Bozho指出，抽象类不应该用@Stateless注释。这是有道理的，但它似乎甚至更早崩溃 - 因为它找不到名为“EntityEJB”的EJB。好吧，似乎在前一种情况下，依赖注入器尝试注入EntityEJB的实例（这是泛型TEJB的超类），它是抽象类，无法实例化（因此不会注入），这会导致异常“无法创建无状态EJB”。整个堆栈跟踪与@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
答案 0 :(得分：2)
从异常堆栈跟踪中我假设你没有no-arg构造函数。确保你有一个，然后再试一次。泛型应该存在问题。
此外，您不应该将抽象类设为无状态bean。所以从这里删除注释：
@Stateless
public abstract class EntityEJB
@EJB注释一个真正的无状态bean接口。
答案 1 :(得分：2)
@EJB是一个用于在课堂中注入它的注释。您不能使用通用类对其进行注释，否则您的Container将无法找到该字段中应使用的实例。
答案 2 :(得分：0)
是的，有可能。它编译并且它可以工作（如果你使用像wildfly或weblogic这样的实体EE应用程序容器）。
在实现接口定义的bean上使用implements（用例如@Local注释）。在抽象类中，您可以实现所有bean实现之间共享的所有方法。只是不要将@Override注释放在任何这些方法上。