java - 服务层 EJB 空指针异常

Question

我有一个 postConstruct 方法:

@EJB
private VisitServiceLocal visitService;

@PostConstruct
void init() {
    eventModel = new DefaultScheduleModel();
    visits = getDoctorVisits();
}

方法:

public List<Visit> getDoctorVisits() {
    doctorId = (Integer) session.getAttribute("userId");
    return visitService.findMyVisits(doctorId);
}

访问服务:

@Override
public List<Visit> findMyVisits(Integer myId) {
    return visitDao.findMyVisits(myId);
}

访问道:

@Override
public List<Visit> findMyVisits(Integer myId) {
    currentDate = new Date();
    try {
        Query q = em.createQuery("SELECT v FROM Visit v WHERE v.doctorId.id = :myId and v.visitStart > :currentDate");
        q.setParameter("myId", myId);
        q.setParameter("currentDate", currentDate);
        List<Visit> visits = q.getResultList();
        return visits;
    } catch (Exception e) {
        System.out.println("Błąd: " + e.getMessage());
        return null;
    }
}

当我运行我的应用程序时出现错误:

com.sun.faces.mgbean.ManagedBeanCreationException: An error occurred performing resource injection on managed bean visitSecretaryMB at com.sun.faces.mgbean.BeanBuilder.invokePostConstruct(BeanBuilder.java:229) at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:105) at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:409) at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:269) at com.sun.faces.el.ManagedBeanELResolver.resolveBean(ManagedBeanELResolver.java:244) at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:116) at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176) at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203) at com.sun.el.parser.AstIdentifier.getValue(AstIdentifier.java:103) at com.sun.el.parser.AstValue.getValue(AstValue.java:179) at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:224) at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109) at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:194) at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:182) at javax.faces.component.UIOutput.getValue(UIOutput.java:169) at org.primefaces.component.outputlabel.OutputLabelRenderer.encodeEnd(OutputLabelRenderer.java:36) at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:312) 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:845) at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:59) at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:47) at org.primefaces.component.dialog.DialogRenderer.encodeContent(DialogRenderer.java:172) at org.primefaces.component.dialog.DialogRenderer.encodeMarkup(DialogRenderer.java:101) at org.primefaces.component.dialog.DialogRenderer.encodeEnd(DialogRenderer.java:43) at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1764) at javax.faces.render.Renderer.encodeChildren(Renderer.java:168) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1757) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1760) at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:402) at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131) at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121) 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:1550) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:343) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217) at pl.ePrzychodnia.filter.FilterLogin.doFilter(FilterLogin.java:49) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:217) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279) 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 org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161) at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231) at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317) at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195) at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860) at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757) at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056) at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229) at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90) at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79) at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54) at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59) at com.sun.grizzly.ContextTask.run(ContextTask.java:71) at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532) at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513) at java.lang.Thread.run(Thread.java:722) Caused by: com.sun.faces.spi.InjectionProviderException: com.sun.enterprise.container.common.spi.util.InjectionException: Exception attempting invoke lifecycle method void pl.ePrzychodnia.mb.VisitSecretaryMB.init() at org.glassfish.faces.integration.GlassFishInjectionProvider.invokePostConstruct(GlassFishInjectionProvider.java:231) at com.sun.faces.mgbean.BeanBuilder.invokePostConstruct(BeanBuilder.java:223) ... 67 more Caused by: com.sun.enterprise.container.common.spi.util.InjectionException: Exception attempting invoke lifecycle method void pl.ePrzychodnia.mb.VisitSecretaryMB.init() at org.glassfish.faces.integration.GlassFishInjectionProvider.invokeLifecycleMethod(GlassFishInjectionProvider.java:393) at org.glassfish.faces.integration.GlassFishInjectionProvider.invokePostConstruct(GlassFishInjectionProvider.java:306) at org.glassfish.faces.integration.GlassFishInjectionProvider.invokePostConstruct(GlassFishInjectionProvider.java:229) ... 68 more Caused by: java.security.PrivilegedActionException: java.lang.reflect.InvocationTargetException at java.security.AccessController.doPrivileged(Native Method) at org.glassfish.faces.integration.GlassFishInjectionProvider.invokeLifecycleMethod(GlassFishInjectionProvider.java:376) ... 70 more Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.glassfish.faces.integration.GlassFishInjectionProvider$2.run(GlassFishInjectionProvider.java:382) ... 72 more Caused by: javax.ejb.EJBException at com.sun.ejb.containers.BaseContainer.processSystemException(BaseContainer.java:5215) at com.sun.ejb.containers.BaseContainer.completeNewTx(BaseContainer.java:5113) at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:4901) at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:2045) at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:1994) at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:222) at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:89) at com.sun.proxy.$Proxy170.findMyVisits(Unknown Source) at pl.ePrzychodnia.mb.VisitSecretaryMB.getDoctorVisits(VisitSecretaryMB.java:322) at pl.ePrzychodnia.mb.VisitSecretaryMB.init(VisitSecretaryMB.java:61) ... 77 more Caused by: java.lang.NullPointerException at pl.ePrzychodnia.dao.serviceClass.VisitService.findMyVisits(VisitService.java:89) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) 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:5388) 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 com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162) at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:144) at sun.reflect.GeneratedMethodAccessor116.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) 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:5360) at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5348) at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:214) ... 81 more

为什么我有这个错误。

但是当我将 JSF 方法 Service 更改为 Dao 时一切正常。

方法:

public List<Visit> getDoctorVisits() {
    doctorId = (Integer) session.getAttribute("userId");
    return visitDao.findMyVisits(doctorId);
}

为什么添加服务层会产生这个错误？在服务层我只导致dao方法。

Answer 1

Caused by: java.lang.NullPointerException
    at pl.ePrzychodnia.dao.serviceClass.VisitService.findMyVisits(VisitService.java:89) at 

您误解了问题。问题不在 JSF 方面。问题出在 EJB 方面。 visitService 已正确注入(inject)，但是在 visitService 内部，visitDao 未正确注入(inject)。

你没有展示所有的代码，但很可能你有一个

@Stateless
public class VisitService implements VisitServiceLocal {

    private VisitDao visitDao;

    @Override
    public List<Visit> findMyVisits(Integer myId) {
        return visitDao.findMyVisits(myId);
    }

}

在这种情况下，您还需要将它注入(inject)到那里:

@Stateless
public class VisitService implements VisitServiceLocal {

    @EJB
    private VisitDao visitDao;

    @Override
    public List<Visit> findMyVisits(Integer myId) {
        return visitDao.findMyVisits(myId);
    }

}

对了，你好像是reinventing/duplicating the DAO pattern虽然已经在使用 JPA。这种双层通常没有任何意义。只需将 VisitService 和 VisitDao 合并到一个 EJB 中即可。