Hibernate EntityManager findById: javax.ejb.EJBException: java.lang.NullPointerException

Question

I am using Hibernate with the Dao´s and JBoss Wildfly

Dao.java

public interface Dao<T> {

   public List<T> findAll();

   public T findById(final Class<T> clazz, final Long id);
}

AbstractDao.java

public abstract class AbstractDao<T extends BaseEntity> implements Dao<T> {

    @PersistenceContext
    private EntityManager em;

    @Override
    public T findById(final Class<T> clazz, final Long id) {
        return this.em.find(clazz, id);
    }

    protected EntityManager getEm() {
        return em;
    }

    protected void setEm(EntityManager em) {
        this.em = em;
    }
}

VeranstaltungDao.java

@Named(value = "veranstaltungDao")
public class VeranstaltungDao extends AbstractDao<Veranstaltung> {

    @Override
    public List<Veranstaltung> findAll() {
        final TypedQuery<Veranstaltung> query = getEm().createQuery(
                "Select a FROM" + Veranstaltung.class.getSimpleName() +" a",
                Veranstaltung.class);

        return query.getResultList();
    }

}

now when I call in my manager the findById function I get the

javax.ejb.EJBException: java.lang.NullPointerException

here is my call:

public class VeranstaltungBO {

    private Dao<Veranstaltung> veranstaltungDao;

    public Veranstaltung getVeranstaltungById(long id){
       // Line below is number 20
       return veranstaltungDao.findById(Veranstaltung.class, id);
    }
}

By starting the JBoss he creates database schema and use the import.sql and when I look in the database all is fine. The stacktrace of this error is saying nothing for me.

    ERROR [io.undertow.request] (default task-4) UT005023: Exception handling request to /AfB/rest/v0/veranstaltungen/1: org.jboss.resteasy.spi.UnhandledException: javax.ejb.EJBException: java.lang.NullPointerException
    at org.jboss.resteasy.core.ExceptionHandler.handleApplicationException(ExceptionHandler.java:76) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.ExceptionHandler.handleException(ExceptionHandler.java:212) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.writeException(SynchronousDispatcher.java:149) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:372) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:179) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:220) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51) [resteasy-jaxrs-3.0.6.Final.jar:]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790) [jboss-servlet-api_3.1_spec-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:61) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:113) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.security.handlers.AuthenticationCallHandler.handleRequest(AuthenticationCallHandler.java:52) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:45) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:61) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:70) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.security.handlers.SecurityInitialHandler.handleRequest(SecurityInitialHandler.java:76) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:25) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:240) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:227) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:73) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:146) [undertow-servlet-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:168) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:687) [undertow-core-1.0.0.Final.jar:1.0.0.Final]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_67]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_67]
    at java.lang.Thread.run(Thread.java:745) [rt.jar:1.7.0_67]
Caused by: javax.ejb.EJBException: java.lang.NullPointerException
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.handleExceptionInOurTx(CMTTxInterceptor.java:190) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInOurTx(CMTTxInterceptor.java:275) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.required(CMTTxInterceptor.java:340) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.processInvocation(CMTTxInterceptor.java:239) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.component.interceptors.CurrentInvocationContextInterceptor.processInvocation(CurrentInvocationContextInterceptor.java:41) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.component.invocationmetrics.WaitTimeInterceptor.processInvocation(WaitTimeInterceptor.java:43) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.security.SecurityContextInterceptor.processInvocation(SecurityContextInterceptor.java:95) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.component.interceptors.ShutDownInterceptorFactory$1.processInvocation(ShutDownInterceptorFactory.java:64) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.component.interceptors.LoggingInterceptor.processInvocation(LoggingInterceptor.java:59) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ee.component.NamespaceContextInterceptor.processInvocation(NamespaceContextInterceptor.java:50)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.component.interceptors.AdditionalSetupInterceptor.processInvocation(AdditionalSetupInterceptor.java:55) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.ContextClassLoaderInterceptor.processInvocation(ContextClassLoaderInterceptor.java:64)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.InterceptorContext.run(InterceptorContext.java:326)
    at org.wildfly.security.manager.WildFlySecurityManager.doChecked(WildFlySecurityManager.java:448)
    at org.jboss.invocation.AccessCheckingInterceptor.processInvocation(AccessCheckingInterceptor.java:61)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.InterceptorContext.run(InterceptorContext.java:326)
    at org.jboss.invocation.PrivilegedWithCombinerInterceptor.processInvocation(PrivilegedWithCombinerInterceptor.java:80)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:61)
    at org.jboss.as.ee.component.ViewService$View.invoke(ViewService.java:185)
    at org.jboss.as.ee.component.ViewDescription$1.processInvocation(ViewDescription.java:182)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:61)
    at org.jboss.as.ee.component.ProxyInvocationHandler.invoke(ProxyInvocationHandler.java:73)
    at de.fhb.appfuerbrandenburg.model.Accessor$$$view1.findById(Unknown Source) [classes:]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_67]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) [rt.jar:1.7.0_67]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_67]
    at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_67]
    at org.jboss.weld.util.reflection.Reflections.invokeAndUnwrap(Reflections.java:401) [weld-core-impl-2.1.2.Final.jar:2014-01-09 09:23]
    at org.jboss.weld.bean.proxy.EnterpriseBeanProxyMethodHandler.invoke(EnterpriseBeanProxyMethodHandler.java:99) [weld-core-impl-2.1.2.Final.jar:2014-01-09 09:23]
    at org.jboss.weld.bean.proxy.EnterpriseTargetBeanInstance.invoke(EnterpriseTargetBeanInstance.java:56) [weld-core-impl-2.1.2.Final.jar:2014-01-09 09:23]
    at org.jboss.weld.bean.proxy.InjectionPointPropagatingEnterpriseTargetBeanInstance.invoke(InjectionPointPropagatingEnterpriseTargetBeanInstance.java:65) [weld-core-impl-2.1.2.Final.jar:2014-01-09 09:23]
    at org.jboss.weld.bean.proxy.ProxyMethodHandler.invoke(ProxyMethodHandler.java:100) [weld-core-impl-2.1.2.Final.jar:2014-01-09 09:23]
    at de.fhb.appfuerbrandenburg.model.Accessor$547179753$Proxy$_$$_Weld$EnterpriseProxy$.findById(Unknown Source) [classes:]
    at de.fhb.appfuerbrandenburg.controller.RestVeranstaltung.getVeranstalltungById(RestVeranstaltung.java:49) [classes:]
    at de.fhb.appfuerbrandenburg.controller.RestVeranstaltung$Proxy$_$$_WeldClientProxy.getVeranstalltungById(Unknown Source) [classes:]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_67]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) [rt.jar:1.7.0_67]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_67]
    at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_67]
    at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:137) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:280) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:234) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:221) [resteasy-jaxrs-3.0.6.Final.jar:]
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:356) [resteasy-jaxrs-3.0.6.Final.jar:]
    ... 29 more
Caused by: java.lang.NullPointerException
    at de.fhb.appfuerbrandenburg.model.VeranstaltungBO.findById(VeranstaltungBO.java:20) [classes:]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_67]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) [rt.jar:1.7.0_67]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_67]
    at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_67]
    at org.jboss.as.ee.component.ManagedReferenceMethodInterceptor.processInvocation(ManagedReferenceMethodInterceptor.java:52)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.WeavedInterceptor.processInvocation(WeavedInterceptor.java:53)
    at org.jboss.as.ee.component.interceptors.UserInterceptorFactory$1.processInvocation(UserInterceptorFactory.java:63)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:407)
    at org.jboss.as.weld.ejb.Jsr299BindingsInterceptor.doMethodInterception(Jsr299BindingsInterceptor.java:82) [wildfly-weld-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.as.weld.ejb.Jsr299BindingsInterceptor.processInvocation(Jsr299BindingsInterceptor.java:93) [wildfly-weld-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.as.ee.component.interceptors.UserInterceptorFactory$1.processInvocation(UserInterceptorFactory.java:63)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.WeavedInterceptor.processInvocation(WeavedInterceptor.java:53)
    at org.jboss.as.ee.component.interceptors.UserInterceptorFactory$1.processInvocation(UserInterceptorFactory.java:63)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.component.invocationmetrics.ExecutionTimeInterceptor.processInvocation(ExecutionTimeInterceptor.java:43) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.jpa.interceptor.SBInvocationInterceptor.processInvocation(SBInvocationInterceptor.java:47) [wildfly-jpa-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:407)
    at org.jboss.weld.ejb.AbstractEJBRequestScopeActivationInterceptor.aroundInvoke(AbstractEJBRequestScopeActivationInterceptor.java:46) [weld-core-impl-2.1.2.Final.jar:2014-01-09 09:23]
    at org.jboss.as.weld.ejb.EjbRequestScopeActivationInterceptor.processInvocation(EjbRequestScopeActivationInterceptor.java:83) [wildfly-weld-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ee.concurrent.ConcurrentContextInterceptor.processInvocation(ConcurrentContextInterceptor.java:45) [wildfly-ee-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.InitialInterceptor.processInvocation(InitialInterceptor.java:21)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:61)
    at org.jboss.as.ee.component.interceptors.ComponentDispatcherInterceptor.processInvocation(ComponentDispatcherInterceptor.java:53)
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.component.interceptors.NonPooledEJBComponentInstanceAssociatingInterceptor.processInvocation(NonPooledEJBComponentInstanceAssociatingInterceptor.java:59) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]
    at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:309)
    at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInOurTx(CMTTxInterceptor.java:273) [wildfly-ejb3-8.0.0.Final.jar:8.0.0.Final]

Please tell me what code you need too, to help

Answer 1

For some reason veranstaltungDao field is not injected. Use proper annotation ( @Autowired in Spring, @Inject in CDI, @EJB in EJB - I'm almost sure it's EJB) to inject it. For example:

import javax.ejb.EJB;

public class VeranstaltungBO {

    @EJB
    private Dao<Veranstaltung> veranstaltungDao;

    public Veranstaltung getVeranstaltungById(long id){
       // Line below is number 20
       return veranstaltungDao.findById(Veranstaltung.class, id);
    }
}

VeranstaltungDao.java

@Stateless
public class VeranstaltungDao extends AbstractDao<Veranstaltung> {

        @Override
        public List<Veranstaltung> findAll() {
            final TypedQuery<Veranstaltung> query = getEm().createQuery(
                    "Select a FROM" + Veranstaltung.class.getSimpleName() +" a",
                    Veranstaltung.class);

            return query.getResultList();
        }

    }

Note, that you need (in above example) EJB bean with type Dao<Veranstaltung> defined. I'm not sure, but maybe you need special interface VeranstaltungDao extending Dao<Veranstaltung> to make it work.

You use pairs: @Stateless - @EJB or @Named - @Inject . Second pair won't work if you don't have your CDI activated, which can happen if you don't have beans.xml file.

@Stateless means, that you want object of given class to be managed by server as EJB bean. @EJB allows to inject existing bean into given property.