Hibernate--一对多与多对一关系的级联操作

傷城~ 2021-08-14 02:15 378阅读 0赞

#### 级联操作 ####

级联操作是指当主控方执行保存、更新或者删除操作时，其关联对象（被控方）也执行相同操作。在映射文件中通过对cascade属性的设置来控制是否对关联对象采用级联操作，级联操作对各种关系都是有效的。

#### 创建实体类 ####

**Customer类：**

public class Customer { 
    	//主键
    	private Long cust_id;
    	
    	private String cust_name;
    	private String cust_source;
    	private String cust_industry;
    	private String cust_level;
    	private String cust_linkman;
    	private String cust_phone;
    	private String cust_mobile;
    	
    	//使用set集合,表达一对多关系
    	private Set<LinkMan> linkMens = new HashSet<LinkMan>();
    	
    	public Set<LinkMan> getLinkMens() { 
    		return linkMens;
    	}
    	public void setLinkMens(Set<LinkMan> linkMens) { 
    		this.linkMens = linkMens;
    	}
    	public Long getCust_id() { 
    		return cust_id;
    	}
    	public void setCust_id(Long cust_id) { 
    		this.cust_id = cust_id;
    	}
    	public String getCust_name() { 
    		return cust_name;
    	}
    	public void setCust_name(String cust_name) { 
    		this.cust_name = cust_name;
    	}
    	public String getCust_source() { 
    		return cust_source;
    	}
    	public void setCust_source(String cust_source) { 
    		this.cust_source = cust_source;
    	}
    	public String getCust_industry() { 
    		return cust_industry;
    	}
    	public void setCust_industry(String cust_industry) { 
    		this.cust_industry = cust_industry;
    	}
    	public String getCust_level() { 
    		return cust_level;
    	}
    	public void setCust_level(String cust_level) { 
    		this.cust_level = cust_level;
    	}
    	public String getCust_linkman() { 
    		return cust_linkman;
    	}
    	public void setCust_linkman(String cust_linkman) { 
    		this.cust_linkman = cust_linkman;
    	}
    	public String getCust_phone() { 
    		return cust_phone;
    	}
    	public void setCust_phone(String cust_phone) { 
    		this.cust_phone = cust_phone;
    	}
    	public String getCust_mobile() { 
    		return cust_mobile;
    	}
    	public void setCust_mobile(String cust_mobile) { 
    		this.cust_mobile = cust_mobile;
    	}
    }

**LinkMan类：**

//联系人实体
    public class LinkMan { 
    	//主键
    	private Long lkm_id;
    	
    	private Character lkm_gender;
    	private String lkm_name;
    	private String lkm_phone;
    	private String lkm_email;
    	private String lkm_qq;
    	private String lkm_mobile;
    	private String lkm_memo;
    	private String lkm_position;
    	
    	//表达多对一关系,外键
    	private Customer customer ;
    	
    	public Customer getCustomer() { 
    		return customer;
    	}
    	public void setCustomer(Customer customer) { 
    		this.customer = customer;
    	}
    	public Long getLkm_id() { 
    		return lkm_id;
    	}
    	public void setLkm_id(Long lkm_id) { 
    		this.lkm_id = lkm_id;
    	}
    	public Character getLkm_gender() { 
    		return lkm_gender;
    	}
    	public void setLkm_gender(Character lkm_gender) { 
    		this.lkm_gender = lkm_gender;
    	}
    	public String getLkm_name() { 
    		return lkm_name;
    	}
    	public void setLkm_name(String lkm_name) { 
    		this.lkm_name = lkm_name;
    	}
    	public String getLkm_phone() { 
    		return lkm_phone;
    	}
    	public void setLkm_phone(String lkm_phone) { 
    		this.lkm_phone = lkm_phone;
    	}
    	public String getLkm_email() { 
    		return lkm_email;
    	}
    	public void setLkm_email(String lkm_email) { 
    		this.lkm_email = lkm_email;
    	}
    	public String getLkm_qq() { 
    		return lkm_qq;
    	}
    	public void setLkm_qq(String lkm_qq) { 
    		this.lkm_qq = lkm_qq;
    	}
    	public String getLkm_mobile() { 
    		return lkm_mobile;
    	}
    	public void setLkm_mobile(String lkm_mobile) { 
    		this.lkm_mobile = lkm_mobile;
    	}
    	public String getLkm_memo() { 
    		return lkm_memo;
    	}
    	public void setLkm_memo(String lkm_memo) { 
    		this.lkm_memo = lkm_memo;
    	}
    	public String getLkm_position() { 
    		return lkm_position;
    	}
    	public void setLkm_position(String lkm_position) { 
    		this.lkm_position = lkm_position;
    	}
    }

#### 级联保存或更新 ####

级联是有方向性的，所谓的方向性指的是，在保存一的一方级联多的一方和在保存多的一方级联一的一方。

**保存客户级联联系人：**  
我们要保存客户，所以客户是主控方，那么需要在客户的映射文件中进行如下配置。

<set name="linkMens" cascade="save-update" >
    			<key column="lkm_cust_id" ></key>
    			<one-to-many class="LinkMan" />
    		</set>

**测试:**

@Test
    	//保存客户 以及客户 下的联系人
    	//cascade:save-update
    	public void fun1(){ 
    		Session session = HibernateUtils.openSession();
    		Transaction tx = session.beginTransaction();
    		//---------------------------------------------
    
    		Customer c = new Customer();
    		c.setCust_name("阿里巴巴");
    		
    		LinkMan lm1 = new LinkMan();
    		lm1.setLkm_name("马云");
    		
    		LinkMan lm2 = new LinkMan();
    		lm2.setLkm_name("张勇");
    		
    		//表达一对多,客户下有多个联系人
    		c.getLinkMens().add(lm1);
    		c.getLinkMens().add(lm2);
    		
    		//表达多对一,联系人属于哪个客户
    		lm1.setCustomer(c);
    		lm2.setCustomer(c);
    		
    		
    		session.save(c);
    // session.save(lm1);
    // session.save(lm2);
    		
    		//---------------------------------------------
    		tx.commit();
    		session.close();
    	}

![在这里插入图片描述][20191006203716528.png]![在这里插入图片描述][20191006203728666.png]**保存联系人级联客户：**  
现在主控方是联系人，所以需要在联系人的映射文件中进行配置：

<many-to-one name="customer" column="lkm_cust_id" class="Customer" cascade="save-update"></many-to-one>

**测试：**

@Test
    	//保存联系人以及联系人对应的客户
    	//cascade:save-update
    	public void fun3(){ 
    		Session session = HibernateUtils.openSession();
    		Transaction tx = session.beginTransaction();
    		//---------------------------------------------
    
    		Customer c = new Customer();
    		c.setCust_name("腾讯");
    		
    		LinkMan lm1 = new LinkMan();
    		lm1.setLkm_name("马化腾");
    		
    		//表达一对多,客户下有多个联系人
    		c.getLinkMens().add(lm1);
    		
    		//表达对对对,联系人属于哪个客户
    		lm1.setCustomer(c);
    		
    		
    		session.save(lm1);
    		
    		//---------------------------------------------
    		tx.commit();
    		session.close();
    	}

![在这里插入图片描述][20191006204646342.png]![在这里插入图片描述][20191006204709592.png]

#### 级联删除 ####

级联删除也是有方向性的，删除客户的同时级联删除联系人，也可以删除联系人的同时级联删除客户（这种需求很少）。

原来JDBC中删除客户和联系人的时候，如果有外键的关系是不可以删除的，使用Hibernate可以帮助我们完成这种功能。

默认情况下如果客户下面还有联系人，Hibernate会将联系人的外键置为null，然后删除客户。

**删除客户的同时级联删除客户的联系人：**  
确定删除的主控方是客户，所以需要在客户元数据中配置：

**测试：**

@Test
    	//测试删除客户时,级联删除客户下的联系人
    	//cascade:delete
    	public void fun2(){ 
    		Session session = HibernateUtils.openSession();
    		Transaction tx = session.beginTransaction();
    		//---------------------------------------------
    
    		//获得要操作的客户对象,阿里巴巴
    		Customer c = session.get(Customer.class,8l);
    		//调用delete删除客户
    		session.delete(c);
    		//---------------------------------------------
    		tx.commit();
    		session.close();
    	}

![在这里插入图片描述][20191006210335646.png]  
![在这里插入图片描述][20191006210345410.png]**删除联系人的时候同时删除客户(慎用)：**  
联系人是主控方，需要在联系人元数据中配置：

<many-to-one name="customer" column="lkm_cust_id" class="Customer" cascade="delete"></many-to-one>

**测试：**

@Test
    	//删除联系人的时候同时删除客户
    	//cascade:delete
    	public void fun2(){ 
    		Session session = HibernateUtils.openSession();
    		Transaction tx = session.beginTransaction();
    		//---------------------------------------------
    		//获得要删除的联系人对象，马化腾
    		LinkMan lm = session.get(LinkMan.class,14l);
    		//调用delete删除联系人
    		session.delete(lm);
    		//---------------------------------------------
    		tx.commit();
    		session.close();
    	}

![在这里插入图片描述][20191006210801551.png]  
![在这里插入图片描述][20191006210811701.png]

[20191006203716528.png]: https://img-blog.csdnimg.cn/20191006203716528.png
[20191006203728666.png]: /images/20210813/7b63e93fc01e4ba187d0d0a0b3874f79.png
[20191006204646342.png]: https://img-blog.csdnimg.cn/20191006204646342.png
[20191006204709592.png]: /images/20210813/857503a951594d5480d5008d2b7ba537.png
[20191006210335646.png]: /images/20210813/9021858fd9fe4e4fa3f872feaf941237.png
[20191006210345410.png]: /images/20210813/a94f12c853a74042871cf7c2ce7d15de.png
[20191006210801551.png]: /images/20210813/e0ac71cb49a848fb8e8cccf8ae798923.png
[20191006210811701.png]: /images/20210813/cefd73d51bef4f798a673de86bb0ab6a.png