Question

持久性API使用在persistence.xml中配置的JTA托管事务。

EntitymanagerProducer.java

@PersistenceContext( unitName = "PRO" )
EntityManager proEm;

@pro
@Produces
public EntityManager createProEntityManager () {
    return this.proEm;
}

以上生成的EntityManager可以注入任何@Stateless bean，其限定符为@Pro，如下所示

@Stateless
@Local( OutRepositoryBeanLocal.class )
@Remote( OutRepositoryRemote.class )
@LocalBean
@TransactionAttribute( TransactionAttributeType.MANDATORY )
public class OutRepositoryBean implements OutRepositoryBeanLocal, OutRepositoryRemote {

    @Inject
    @Pro
    private EntityManager entityManager;

    @Inject
    OutRepository      outRepository;

    /**
     * 
     */
    @PostConstruct
    private void init () {
        this.outRepository.setEntityManager( this.entityManager );
    }

上面的代码无效地运行，没有错误。但是，在将作业委托给@Dependent子类时，问题就出现了，

OutRepository.java

@Dependent
public class OutRepository extends BaseService< Out, Long > {


public OutRepository() {
    // TODO Auto-generated constructor stub
}


@Override
protected Class< Out > t () {
    return Out.class;
}
public List< Out > getOuts ( Long proId, String Out) { 
    CriteriaBuilder builder = this.entityManager.getCriteriaBuilder(); <= NPE
    CriteriaQuery< Out > criteriaQuery = builder.createQuery( t() );
    Root< Out > endPointConfig = criteriaQuery.from( t() );
    criteriaQuery.select( endPoint ); 
    TypedQuery< Out > query = this.entityManager.createQuery( criteriaQuery );
    return query.getResultList();
}

BaseService.java是包含通用crud方法的abstract类。

BaseService.java

@Dependent
public abstract class BaseService< T, I extends Serializable > implements BaseEntity< T, I > {


    protected abstract Class< T > t ();

    @PostConstruct
    protected abstract void init ();

    public PersistenceUnitUtil persistenceUnitUtil;
    public EntityManager       entityManager;


    @TransactionAttribute( TransactionAttributeType.MANDATORY )
    @Override
    public T save ( T t ) {
        this.entityManager.persist( t ); 
        return t;
    }

调用outRepsitory.save()时，事务中没有问题，一切都很好。然而，outRepository.getOuts(Long proId,String Out)，发生以下异常

[2/7/18 18:19:36:187 IST] 0000003d BusinessExcep E   CNTR0020E: EJB threw an unexpected (non-declared) exception during invocation of method "getOuts" on bean "BeanId(pro-ear#pro-web-0.0.1-SNAPSHOT.war#OutRepositoryBean, null)". Exception data: java.lang.NullPointerException
    at org.apache.openjpa.persistence.meta.MetamodelImpl.populate(MetamodelImpl.java:321)
    at org.apache.openjpa.persistence.meta.MetamodelImpl.instantiate(MetamodelImpl.java:255)
    at org.apache.openjpa.persistence.meta.MetamodelImpl.find(MetamodelImpl.java:224)
    at org.apache.openjpa.persistence.meta.MetamodelImpl.<init>(MetamodelImpl.java:89)
    at org.apache.openjpa.persistence.EntityManagerFactoryImpl.getMetamodel(EntityManagerFactoryImpl.java:346)
    at org.apache.openjpa.persistence.EntityManagerFactoryImpl.getCriteriaBuilder(EntityManagerFactoryImpl.java:333)
    at org.apache.openjpa.persistence.EntityManagerImpl.getCriteriaBuilder(EntityManagerImpl.java:1649)
    at org.apache.openjpa.persistence.EntityManagerImpl.getCriteriaBuilder(EntityManagerImpl.java:101)
    at com.ibm.ws.jpa.management.JPAExEmInvocation.getCriteriaBuilder(JPAExEmInvocation.java:394)
    at com.ibm.ws.jpa.management.JPAEntityManager.getCriteriaBuilder(JPAEntityManager.java:494)
    at com.org.uck.pro.db.out.control.OutRepository.getOuts(OutRepository.java:68)
    at com.org.uck.pro.db.out.control.OutRepositoryBean.getOuts(OutRepositoryBean.java:108)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
    at java.lang.reflect.Method.invoke(Method.java:611)
    at com.ibm.ejs.container.EJSContainer.invokeProceed(EJSContainer.java:6207)
    at com.ibm.ejs.container.interceptors.InvocationContextImpl.proceed(InvocationContextImpl.java:568)
    at org.apache.webbeans.ejb.common.interceptor.OpenWebBeansEjbInterceptor.callInterceptorsAndDecorators(OpenWebBeansEjbInterceptor.java:528)
    at org.apache.webbeans.ejb.common.interceptor.OpenWebBeansEjbInterceptor.callToOwbInterceptors(OpenWebBeansEjbInterceptor.java:200)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
    at java.lang.reflect.Method.invoke(Method.java:611)
    at com.ibm.ejs.container.interceptors.InterceptorProxy.invokeInterceptor(InterceptorProxy.java:227)
    at com.ibm.ejs.container.interceptors.InvocationContextImpl.proceed(InvocationContextImpl.java:548)
    at org.apache.webbeans.ejb.WSEJBInterceptor.callToOwbInterceptors(WSEJBInterceptor.java:152)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
    at java.lang.reflect.Method.invoke(Method.java:611)
    at com.ibm.ejs.container.interceptors.InterceptorProxy.invokeInterceptor(InterceptorProxy.java:227)
    at com.ibm.ejs.container.interceptors.InvocationContextImpl.proceed(InvocationContextImpl.java:548)
    at com.ibm.ejs.container.interceptors.InvocationContextImpl.doAroundInvoke(InvocationContextImpl.java:229)
    at com.ibm.ejs.container.EJSContainer.invoke(EJSContainer.java:6098)
    at com.org.uck.pro.db.out.boundary.EJSLocal1SLOutRepositoryBean_03076fb6.getOuts(EJSLocal1SLOutRepositoryBean_03076fb6.java)
    at com.org.uck.pro.ejb.outs.control.OutBean.getOuts(OutBean.java:109)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

NullPointerException上的

CriteriaBuilder builder = this.entityManager.getCriteriaBuilder();，尝试使用entitymanager调用super.entitymanger仍然存在相同的错误。

- 感谢。

Answer 1

BaseService中没有Inject注释

应该就像你在OutRepositoryBean中完成它一样

@Inject @Pro
public EntityManager entityManager;

如何在非EJB @Dependent子类中获取CDI生成的实体管理器，抛出NPE？

1 个答案: