在Hibernate的EmptyInterceptor中注入JPA的实体管理器

Question

我在数据访问层中将JPA-2.0与Hibernate一起使用。

为了进行审核日志记录，我通过在persistence.xml中配置以下属性来使用Hibernate的EmptyInterceptor：

<property name="hibernate.ejb.interceptor"  
                value="com.mycom.audit.AuditLogInterceptor" />

凡 AuditLogInterceptor 扩展Hibernate的’ org.hibernate.EmptyInterceptor ‘。

public class AuditLogInterceptor extends EmptyInterceptor {

    private Long userId;

    public AuditLogInterceptor() {}

    @Override  
    public boolean onSave(Object entity, Serializable id, Object[] state,  
            String[] propertyNames, Type[] types) throws CallbackException {  
        // Need to perform database operations using JPA entity manager
        return false;  
    }

   @Override
    public boolean onFlushDirty(Object entity, Serializable id,
            Object[] currentState, Object[] previousState,
            String[] propertyNames, Type[] types) {
        // other code here        
        return false;
    }

    @Override  
    public void postFlush(Iterator iterator) throws CallbackException {  
        System.out.println("I am on postFlush");
        // other code here 
    }  
}

我在数据访问层中使用JPA实体管理器来执行数据库操作。JPA配置如下所示：

<bean id="entityManagerFactory"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
        p:persistenceUnitName="PersistenceUnit"
        p:persistenceXmlLocation="classpath*:persistence.xml"
        p:dataSource-ref="dataSource" p:jpaVendorAdapter-ref="jpaAdapter">
        <property name="loadTimeWeaver">
            <bean
                class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver" />
        </property>
    </bean>

我的AbstractDAO是：

public class AbstractDao<T, ID extends Serializable> {

    private final transient Class<T> persistentClass;

    protected transient EntityManager entityManager;

    @SuppressWarnings("unchecked")
    public AbstractDao() {

        this.persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
    }

    @PersistenceContext
    public final void setEntityManager(final EntityManager entityMgrToSet) {

        this.entityManager = entityMgrToSet;
    }

    public final Class<T> getPersistentClass() {

        return persistentClass;
    }

    public final void persist(final T entity) {

         entityManager.persist(entity);       
    }

}

我想在“ AuditLogInterceptor”中注入JPA实体管理器，以便可以像我的抽象DAO在“
AuditLogInterceptor”中执行数据库操作。

任何的想法？什么是正确的解决方案？

Answer 1

我有一个简单的方法可以在“ AuditLogInterceptor”中使用JPA实体管理器执行数据库操作

我创建了下面的类，该类将提供应用程序上下文参考：

@Component("applicationContextProvider")
    public class ApplicationContextProvider implements ApplicationContextAware {
        private static ApplicationContext context;

        public static ApplicationContext getApplicationContext() {
            return context;
        }

        @Override
        public void setApplicationContext(ApplicationContext ctx) {
            context = ctx;
        }
    }

创建的数据访问类：

@Repository("myAuditDAO")
public class myAuditDAO<T, ID extends Serializable> {

    private final transient Class<T> persistentClass;

    protected transient EntityManager entityManager;

    @SuppressWarnings("unchecked")
    public MyDAO() {

        this.persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
    }

    @PersistenceContext
    public final void setEntityManager(final EntityManager entityMgrToSet) {

        this.entityManager = entityMgrToSet;
    }

    public final Class<T> getPersistentClass() {

        return persistentClass;
    }

    public final T findById(final ID theId) {

        return entityManager.find(persistentClass, theId);
    }

    public final void persist(final T entity) {

        entityManager.persist(entity);
    }

    public final void merge(final T entity) {

        entityManager.merge(entity);
    }
}

并在“ AuditLogInterceptor”中使用“ ApplicationContextProvider”来获取“
MyAuditDAO”的引用，该引用具有JPA实体管理器作为在DAO初始化期间注入的属性。现在，借助“ MyAuditDAO”，我可以执行数据库操作。

public class AuditLogInterceptor extends EmptyInterceptor {

    @Override  
    public void postFlush(Iterator iterator) throws CallbackException {

      // Here we can get the MyAuditDao reference and can perform persiste/merge options
       MyAuditDao myAuditDao = (MyAuditDao ) ApplicationContextProvider.getApplicationContext().getBean("myAuditDao");

      //  myAuditDao.persist(myEntity);

    }  
}