单 DAO &通用 CRUD 方法(JPA/Hibernate + Spring) [英] Single DAO & generic CRUD methods (JPA/Hibernate + Spring)

问题描述

按照我之前的问题，DAO 和服务层(JPA/Hibernate + Spring)，我决定在使用 JPA/Hibernate、Spring 和 Wicket 的应用程序中为我的数据层(至少在开始时)只使用一个 DAO.建议使用通用 CRUD 方法，但我不太确定如何使用 JPA 实现它.你能给我一个例子或分享一个关于这个的链接吗?

Following my previous question, DAO and Service layers (JPA/Hibernate + Spring), I decided to use just a single DAO for my data layer (at least at the beginning) in an application using JPA/Hibernate, Spring and Wicket. The use of generic CRUD methods was proposed, but I'm not very sure how to implement this using JPA. Could you please give me an example or share a link regarding this?

推荐答案

这是一个示例界面:

public interface GenericDao<T, PK extends Serializable> {
    T create(T t);
    T read(PK id);
    T update(T t);
    void delete(T t);
}

还有一个实现:

public class GenericDaoJpaImpl<T, PK extends Serializable> 
    implements GenericDao<T, PK> {

    protected Class<T> entityClass;

    @PersistenceContext
    protected EntityManager entityManager;

    public GenericDaoJpaImpl() {
        ParameterizedType genericSuperclass = (ParameterizedType) getClass()
             .getGenericSuperclass();
        this.entityClass = (Class<T>) genericSuperclass
             .getActualTypeArguments()[0];
    }

    @Override
    public T create(T t) {
        this.entityManager.persist(t);
        return t;
    }

    @Override
    public T read(PK id) {
        return this.entityManager.find(entityClass, id);
    }

    @Override
    public T update(T t) {
        return this.entityManager.merge(t);
    }

    @Override
    public void delete(T t) {
        t = this.entityManager.merge(t);
        this.entityManager.remove(t);
    }
}

这篇关于单 DAO &通用 CRUD 方法(JPA/Hibernate + Spring)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！