JPA service里面的两个文件

package com.hunqing.user.service;import com.hunqing.user.entity.User;/** * 用户操作接口 *  * @author *  * <p>Modification History:</p> * <p>Date       Author      Description</p> * <p>------------------------------</p> * <p>  </p> * <p>  </p> */public interface IUserService {/** * Save. *  * @param user the user */public void save(User user);/** * Delete. *  * @param String userName */public void delete(String userName);/** * Update. *  * @param user the user */public void update(User user);/** * Find. *  * @param user the user */public User find(String userName);}

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package com.hunqing.user.service;import javax.persistence.EntityManager;import javax.persistence.PersistenceContext;import org.springframework.stereotype.Service;import org.springframework.transaction.annotation.Transactional;import com.hunqing.user.entity.User;@Service @Transactionalpublic class UserService implements IUserService {@PersistenceContextEntityManager em;public void delete(String userName) {   //throws XXX  //抛出的例外叫用户例外，客户端捕获//运行期的异常叫运行期例外  spring会捕获运行期例外，自动回滚事物//客户例外不会回滚事物em.remove(em.getReference(User.class, userName));}public User find(String userName) {return em.find(User.class,userName);}public void save(User user) {em.persist(user);}public void update(User user) {em.merge(user);}}