我正在开发Java EE应用程序，并且遇到一些错误，我不确定这是否是我的代码问题。
我创建了一个名为Staff的实体类，并为该实体类（Facade）创建了一个无状态会话bean，以便从WAR应用程序中访问它。但是，最初我有一个Managed Bean，它使用@EJB批注对Facade进行引用，并且工作正常。但是，当我尝试在另一个Managed Bean中引用它时，以下错误开始显示：
Severe: Exception during lifecycle processing
java.lang.NullPointerException
at com.sun.enterprise.deployment.util.ComponentValidator.accept(ComponentValidator.java:554)
at com.sun.enterprise.deployment.util.DefaultDOLVisitor.accept(DefaultDOLVisitor.java:78)
at com.sun.enterprise.deployment.util.ComponentValidator.accept(ComponentValidator.java:123)
at com.sun.enterprise.deployment.util.ApplicationValidator.accept(ApplicationValidator.java:152)
at org.glassfish.web.deployment.util.WebBundleValidator.accept(WebBundleValidator.java:81)
at com.sun.enterprise.deployment.BundleDescriptor.visit(BundleDescriptor.java:625)
at org.glassfish.web.deployment.descriptor.WebBundleDescriptorImpl.visit(WebBundleDescriptorImpl.java:1999)
at org.glassfish.web.deployment.descriptor.WebBundleDescriptorImpl.visit(WebBundleDescriptorImpl.java:1989)
at com.sun.enterprise.deployment.util.ApplicationValidator.accept(ApplicationValidator.java:131)
at com.sun.enterprise.deployment.BundleDescriptor.visit(BundleDescriptor.java:625)
at com.sun.enterprise.deployment.archivist.ApplicationArchivist.validate(ApplicationArchivist.java:703)
at com.sun.enterprise.deployment.archivist.ApplicationArchivist.openWith(ApplicationArchivist.java:248)
at com.sun.enterprise.deployment.archivist.ApplicationFactory.openWith(ApplicationFactory.java:232)
at org.glassfish.javaee.core.deployment.DolProvider.processDOL(DolProvider.java:193)
at org.glassfish.javaee.core.deployment.DolProvider.load(DolProvider.java:227)
at org.glassfish.javaee.core.deployment.DolProvider.load(DolProvider.java:96)
at com.sun.enterprise.v3.server.ApplicationLifecycle.loadDeployer(ApplicationLifecycle.java:881)
at com.sun.enterprise.v3.server.ApplicationLifecycle.setupContainerInfos(ApplicationLifecycle.java:821)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:377)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:219)
at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:491)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:539)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:535)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:360)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2.execute(CommandRunnerImpl.java:534)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$3.run(CommandRunnerImpl.java:565)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$3.run(CommandRunnerImpl.java:557)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:360)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:556)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1464)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1300(CommandRunnerImpl.java:109)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1846)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1722)
at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:534)
at com.sun.enterprise.v3.admin.AdminAdapter.onMissingResource(AdminAdapter.java:224)
at org.glassfish.grizzly.http.server.StaticHttpHandlerBase.service(StaticHttpHandlerBase.java:189)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:283)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:200)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:132)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:111)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:536)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:571)
at java.lang.Thread.run(Thread.java:748)
曾经尝试在线搜索解决方案，但未找到任何结果。如果有人可以回答，将不胜感激。