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java - 调用EJB时​​出现空指针异常

转载 作者:行者123 更新时间:2023-12-01 15:38:24 25 4
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以下代码似乎在 QuestionRepository 类中抛出 NullPointerException,但我无法修复它。不知道我上下文依赖注入(inject)有没有做错什么?

实体

@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";

存储库

@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;
}
}

异常(exception):

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>

项目结构:

enter image description here

最佳答案

尝试将项目合并为一个。当使用多个项目时,框架可能会出现错误。

关于java - 调用EJB时​​出现空指针异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8490757/

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