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調用EJB時​​的Nullpointer異常

2011-12-13 100 views
0

下面的代碼似乎在QuestionRepository類中拋出了NullPointerException，但我無法解決它。我不知道我是否在上下文依賴注入方面做了任何錯誤？調用EJB時​​的Nullpointer異常

實體

@Entity 
@NamedQueries({ 
    @NamedQuery(name=Question.ALL, query="SELECT q FROM Question q") 
}) 
public class Question implements Serializable { 

    private static final long serialVersionUID = 2402027045394206281L; 

    public static final String ALL = "Question.all";

庫

@Named 
public class QuestionRepository { 

    @PersistenceContext(unitName="SertifikatPU") 
    private EntityManager entityManager; 

    public List<Question> all() { 
     TypedQuery<Question> query = entityManager.createNamedQuery(Question.ALL, Question.class); 
     return query.getResultList(); 
    } 
}

EJB

@Local(QuestionLocal.class) 
@Stateless 
public class QuestionServiceBean implements QuestionLocal { 

    @Inject 
    private QuestionRepository questionRepository; 

    @Override 
    public List<Question> findAllQuestions() { 
     return questionRepository.all(); 
    } 
}

支持bean

@ManagedBean 
@ViewScoped 
public class QuestionIndexBean implements Serializable { 

    private static final long serialVersionUID = 4228471944163051591L; 

    @Inject 
    private QuestionLocal questionBean; 

    private List<Question> questions; 

    public void init() { 
     setQuestions(questionBean.findAllQuestions()); 
    } 

    public List<Question> getQuestions() { 
     return questions; 
    } 

    public void setQuestions(List<Question> questions) { 
     this.questions = questions; 
    } 
}

例外：

WARNING: A system exception occurred during an invocation on EJB QuestionServiceBean method public java.util.List com.mycompany.application.QuestionServiceBean.findAllQuestions() 
javax.ejb.EJBException 
    at com.sun.ejb.containers.BaseContainer.processSystemException(BaseContainer.java:5193) 
    at com.sun.ejb.containers.BaseContainer.completeNewTx(BaseContainer.java:5091) 
    at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:4879) 
    at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:2039) 
    at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:1990) 
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:222) 
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:88) 
    at $Proxy208.findAllQuestions(Unknown Source) 
    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 org.jboss.weld.util.reflection.SecureReflections$13.work(SecureReflections.java:305) 
    at org.jboss.weld.util.reflection.SecureReflectionAccess.run(SecureReflectionAccess.java:54) 
    at org.jboss.weld.util.reflection.SecureReflectionAccess.runAsInvocation(SecureReflectionAccess.java:163) 
    at org.jboss.weld.util.reflection.SecureReflections.invoke(SecureReflections.java:299) 
    at org.jboss.weld.bean.proxy.EnterpriseBeanProxyMethodHandler.invoke(EnterpriseBeanProxyMethodHandler.java:125) 
    at org.jboss.weld.bean.proxy.EnterpriseTargetBeanInstance.invoke(EnterpriseTargetBeanInstance.java:62) 
    at org.jboss.weld.bean.proxy.ProxyMethodHandler.invoke(ProxyMethodHandler.java:125) 
    at com.mycompany.application.org$jboss$weld$bean-SertifikatEJB_jar-SessionBean-QuestionServiceBean_$$_WeldProxy.findAllQuestions(org$jboss$weld$bean-SertifikatEJB_jar-SessionBean-QuestionServiceBean_$$_WeldProxy.java) 
    at com.mycompany.web.QuestionIndexBean.init(QuestionIndexBean.java:25) 
    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.el.parser.AstValue.invoke(AstValue.java:234) 
    at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:297) 
    at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:43) 
    at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:56) 
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105) 
    at com.sun.faces.facelets.tag.jsf.core.DeclarativeSystemEventListener.processEvent(EventHandler.java:128) 
    at javax.faces.component.UIComponent$ComponentSystemEventListenerAdapter.processEvent(UIComponent.java:2508) 
    at javax.faces.event.SystemEvent.processListener(SystemEvent.java:106) 
    at com.sun.faces.application.ApplicationImpl.processListeners(ApplicationImpl.java:2129) 
    at com.sun.faces.application.ApplicationImpl.invokeComponentListenersFor(ApplicationImpl.java:2077) 
    at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:286) 
    at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:244) 
    at javax.faces.application.ApplicationWrapper.publishEvent(ApplicationWrapper.java:670) 
    at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:108) 
    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:594) 
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1539) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) 
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655) 
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595) 
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:98) 
    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:91) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:162) 
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:330) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231) 
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:174) 
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:828) 
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:725) 
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1019) 
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225) 
    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:662) 
Caused by: java.lang.NullPointerException 
    at com.mycompany.repository.QuestionRepository.all(QuestionRepository.java:17) 
    at com.mycompany.application.QuestionServiceBean.findAllQuestions(QuestionServiceBean.java:21) 
    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 org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052) 
    at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124) 
    at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5366) 
    at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:619) 
    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800) 
    at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571) 
    at org.jboss.weld.ejb.SessionBeanInterceptor.aroundInvoke(SessionBeanInterceptor.java:46) 
    at sun.reflect.GeneratedMethodAccessor109.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
    at java.lang.reflect.Method.invoke(Method.java:597) 
    at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861) 
    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800) 
    at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571) 
    at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162) 
    at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:144) 
    at sun.reflect.GeneratedMethodAccessor108.invoke(Unknown Source) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
    at java.lang.reflect.Method.invoke(Method.java:597) 
    at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861) 
    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800) 
    at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:370) 
    at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:5338) 
    at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5326) 
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:214) 
    ... 61 more

持久性XML

<?xml version="1.0" encoding="UTF-8"?> 
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"> 
    <persistence-unit name="SertifikatPU"> 
     <jta-data-source>jdbc/sertifikat</jta-data-source> 
     <exclude-unlisted-classes>false</exclude-unlisted-classes> 
    </persistence-unit> 
</persistence>

項目結構：

enter image description here

來源

2011-12-13 LuckyLuke

+0

請加QuestionRepository'的'代碼的那一刻被初始化。 – tobiasbayer

+1

@CodeBrickie - 它已經加入:) –

+2

請在這裏粘貼你的'persistence.xml'。顯然'entityManager'是'null' –

回答

1

嘗試合併項目之一。也許在使用多個項目時，框架中存在一個錯誤。

來源

2011-12-13 15:12:13

0

你的問題位於你的課上QuestionRepository。

如果我沒有看錯，這是一個簡單的類，而不是服務器託管類。這是什麼意思？這意味着，由於這個原因，這段代碼

@PersistenceContext(unitName="SertifikatPU") 
    private EntityManager entityManager;

什麼也不做，因爲類是由你實例化，也不是由服務器，所以持久化上下文是從視圖類的點不得而知。結果是，在這另一段代碼

public List<Question> all() { 
     TypedQuery<Question> query = entityManager.createNamedQuery(Question.ALL, Question.class); 
     return query.getResultList(); 
    }

entityManager將爲空，因此它會導致空指針異常。

解決方案？作爲例子，也要將QuestionRepository聲明爲一個EJB。通過這種方式，持久化上下文的注入將在服務器和實體管理器自動完成將在您嘗試執行查詢

來源

2015-12-14 18:25:02 Facepalmed

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