java - hibernate 中的 PreInsert 和 PreUpdate 事件监听器

Question

我已经使用 PreInsertEventListener 和 PreUpdateEventListener 事件监听器在表中插入创建日期和更新日期。
我面临的问题是，当我在数据库中保存实体时，创建日期无法插入表中，就像在更新记录时插入更新日期一样，它也不会插入更新日期。

我的代码示例如下所示:

监听类:

public class PreInsertListener implements PreInsertEventListener,  
                                          PreUpdateEventListener 
{
    @Override
    public boolean onPreInsert(PreInsertEvent arg0) {
        City.class.cast(arg0.getEntity()).setCreated_date(new Date());
        return false;
    }

    @Override
    public boolean onPreUpdate(PreUpdateEvent arg0) {
        System.out.println("Update event......");
        City.class.cast(arg0.getEntity()).setUpdated_date(new Date());
        return false;
    }
}

hibernate 连接类:

public class HibernateUtil 
{

    private static final SessionFactory sessionFactory;

    static {
        try {
            AnnotationConfiguration config = new AnnotationConfiguration();
            config.setListener("pre-insert", new PreInsertListener());
            config.setListener("pre-update", new PreInsertListener());
            sessionFactory = config.configure().buildSessionFactory();;

        } catch (Throwable ex) {
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

DAO 中的实体保存和更新方法:

public Long saveCity(String cityName)
{
    Session session = HibernateUtil.getSessionFactory().openSession();
    Transaction transaction = null;
    Long cityId = null;
    try {
        transaction = session.beginTransaction();
        City city = new City();
        city.setName(cityName);
        cityId = (Long) session.save(city);
        //session.flush();
        transaction.commit();
    } catch (HibernateException e) {
        transaction.rollback();
        e.printStackTrace();
    } finally {
        session.close();
    }
    return cityId;
}

public void updateCity(Long cityId, String cityName)
{
    Session session = HibernateUtil.getSessionFactory().openSession();
    Transaction transaction = null;
    try {
        transaction = session.beginTransaction();
        City city = (City) session.get(City.class, cityId);
        city.setName(cityName);
        session.update(city);
        //session.flush();
        transaction.commit();
    } catch (HibernateException e) {
        transaction.rollback();
        e.printStackTrace();
    } finally {
        session.close();
    }
}

我的测试类:

public class Main 
{
    public static void main(String[] args) {

        CityDAO cityDAO = new CityDAO();

        long cityId1 = cityDAO.saveCity("New York");

        cityDAO.updateCity(cityId1, "Paris");
    }
 }

如果我使用 session.flush() 它将同时插入创建日期和更新日期，但每次我调用 flush 方法时都会执行更新查询。目前我评论了代码以调用 session.flush() 方法，如代码所示。

这个问题的解决方案是什么？

Answer 1

我最近在集成 Spring4 和 Hibernate5 时遇到了同样的问题。 这是我的 BaseEntity 类。

@MappedSuperclass
public class BaseEntity implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(nullable = false, updatable = false)
    private Date createDate;

    @Column(nullable = false)
    private Date modifyDate;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public Date getCreateDate() {
        return createDate;
    }

    public void setCreateDate(Date createDate) {
        this.createDate = createDate;
    }

    public Date getModifyDate() {
        return modifyDate;
    }

    public void setModifyDate(Date modifyDate) {
        this.modifyDate = modifyDate;
    }
}

首先，您需要定义 EntityListener 类。

public class EntityListener implements PreInsertEventListener, PreUpdateEventListener {

    private static final String CREATE_DATE_PROPERTY = "createDate";

    private static final String MODIFY_DATE_PROPERTY = "modifyDate";

    @Override
    public boolean onPreInsert(PreInsertEvent event) {

        if (event.getEntity() instanceof BaseEntity){
            //property name of entity
            String[] propertyNames = event.getPersister().getEntityMetamodel().getPropertyNames();
            //property value of entity
            Object[] state = event.getState();
            for (int i = 0; i < propertyNames.length ; i ++) {
                if (CREATE_DATE_PROPERTY.equals(propertyNames[i]) || MODIFY_DATE_PROPERTY.equals(propertyNames[i])){
                    state[i] = new Date();
                }
            }
        }

        return false;
    }

    @Override
    public boolean onPreUpdate(PreUpdateEvent event) {

        if (event.getEntity() instanceof BaseEntity){
            //property name of entity
            String[] propertyNames = event.getPersister().getEntityMetamodel().getPropertyNames();
            //property value of entity
            Object[] state = event.getState();
            for (int i = 0; i < propertyNames.length ; i ++) {
                if (MODIFY_DATE_PROPERTY.equals(propertyNames[i])){
                    state[i] = new Date();
                }
            }
        }

        return false;
    }
}

然后，您应该注册实体事件监听器。

@SuppressWarnings("unchecked")
@Component
public class EntityEventListenerRegistry {

    @Autowired
    private SessionFactory sessionFactory;

    /**
     * EventListenerRegistry:http://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#annotations-jpa-entitylisteners
     */
    @PostConstruct
    public void registerListeners(){
        EventListenerRegistry eventListenerRegistry = ((SessionFactoryImplementor) sessionFactory).getServiceRegistry().getService(EventListenerRegistry.class);
        eventListenerRegistry.prependListeners(EventType.PRE_INSERT, EntityListener.class);
        eventListenerRegistry.prependListeners(EventType.PRE_UPDATE, EntityListener.class);
    }

}

效果很好，希望对你有帮助。