CascadeType.REMOVE

/*******************************************************************************
 * Copyright (c) 2005, 2014 springside.github.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *******************************************************************************/
package com.entity;

import javax.persistence.*;

import org.apache.commons.lang3.builder.ToStringBuilder;
import org.hibernate.validator.constraints.NotBlank;

//JPA标识
@Entity
@Table(name = "t_task")
public class Task extends IdEntity {

	private String title;
	private String description;
	private User user;

	// JSR303 BeanValidator的校验规则
	@NotBlank
	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	// JPA 基于USER_ID列的多对一关系定义
	@ManyToOne(cascade = CascadeType.REMOVE)
	@JoinColumn(name = "user_id")
	public User getUser() {
		return user;
	}

	public void setUser(User user) {
		this.user = user;
	}

	@Override
	public String toString() {
		return ToStringBuilder.reflectionToString(this);
	}
}

@Test
    public void remove(){
        Task task = taskDao.findOne(1L);
        long userId = task.getUser().getId();
        //删除task时，user也被删除
        taskDao.delete(task);

       User user = userDao.findOne(userId);

        logger.debug("user is {}",user);

    }

16:45:51.071 [main] DEBUG com.repository.TaskDaoTest - user is null



如果反过来，删除User对象，User对象上并未绑定任何关联关系

     User user  = userDao.findOne(2L);

        //删除user
        userDao.delete(user);

        //加载关联的task
         Task task = taskDao.findOne(1L);

        //重新加载user
        user  = userDao.findOne(2L);


        logger.debug("task is {}",task);
         logger.debug("task.user is {}",task.getUser());
        logger.debug("user is {}",user);

结果是只删除了user对象 task对象未删除,task关联的user对象在事务未结束时还可以访问
16:54:00.962 [main] DEBUG com.repository.TaskDaoTest - task is com.entity.Task@2a79db08[title=Study PlayFramework 2.0,description=http://www.playframework.org/,user=com.entity.User@367970fa[loginName=user,name=Calvin,plainPassword=<null>,password=2488aa0c31c624687bd9928e0a5d29e7d1ed520b,salt=6d65d24122c30500,roles=user,registerDate=2012-06-04 02:00:00.0,id=2],id=1]

17:09:56.307 [main] DEBUG com.repository.TaskDaoTest - task.user is com.entity.User@c734212[loginName=user,name=Calvin,plainPassword=<null>

16:54:00.973 [main] DEBUG com.repository.TaskDaoTest - user is null



若改为 CascadeType.PERSIST 则未级联删除 输出
16:47:08.936 [main] DEBUG com.repository.TaskDaoTest - user is com.entity.User@3ef6551c[loginName=user,name=Calvin,plainPassword=<null>,password=2488aa0c31c624687bd9928e0a5d29e7d1ed520b,salt=6d65d24122c30500,roles=user,registerDate=2012-06-04 02:00:00.0,id=2]