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Hibernate manytomany

发表于: 2012-04-20   作者:cnge06   来源:转载   浏览:
摘要: @manytomany   关系维护端   @Entity public class Test1 { public String id; public String name; public Set<Test2> test2; @Id @GenericGenerator(name = "idGenerator", s

@manytomany

 

关系维护端

 

@Entity
public class Test1 {
	public String id;
	public String name;
	public Set<Test2> test2;
	@Id
	@GenericGenerator(name = "idGenerator", strategy = "org.hibernate.id.UUIDGenerator")
	@GeneratedValue(generator = "idGenerator")
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	@Column
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@ManyToMany(targetEntity=com.peyey.coo.model.Test2.class,
			cascade = {javax.persistence.CascadeType.PERSIST, javax.persistence.CascadeType.MERGE}
			)
	@JoinTable(name="test1test2",joinColumns=@JoinColumn(name="test1_id",referencedColumnName="id"),
	inverseJoinColumns={@JoinColumn(name="test2_id",referencedColumnName="id")})
	public Set<Test2> getTest2() {
		return test2;
	}
	public void setTest2(Set<Test2> test2) {
		this.test2 = test2;
	}

}
 

关系被维护端:

 

@Entity
public class Test2 {
	public String id;
	public String name;
	public Set<Test1> test1;
	@Id
	@GenericGenerator(name = "idGenerator", strategy = "org.hibernate.id.UUIDGenerator")
	@GeneratedValue(generator = "idGenerator")
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	@Column
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@ManyToMany(
			cascade = {javax.persistence.CascadeType.PERSIST, javax.persistence.CascadeType.MERGE},
			targetEntity=com.peyey.coo.model.Test1.class,
			mappedBy="test2"
			)
	public Set<Test1> getTest1() {
		return test1;
	}
	public void setTest1(Set<Test1> test1) {
		this.test1 = test1;
	}
}
 

 

 

增删改操作:

public void create(){
		/* 
		 * Test1维护关系
		 * 通过Test1级联增加Test2
		 * 
		 * 
		 */
		Test1 test1a=new Test1();
		Test2 test2a=new Test2();
		test2a.setName("test2a");
		Test2 test2b=new Test2();
		test2b.setName("test2b");
		/**
		 * Test2的记录需要各自添加
		 * 所谓的级联增加,只是Test1对中间表而言
		 */
		test2Dao.save(test2a);
		test2Dao.save(test2b);
		Set<Test2> test2=new HashSet<Test2>();
		test2.add(test2a);
		test2.add(test2b);
		test1a.setName("aaaa");
		test1a.setTest2(test2);
		test1Dao.save(test1a);
	}
	
	
	

	@Override
	public void update() {
		/**
		 * 删除中间表的记录
		 * 需要从Test1表出发,remove掉关联记录,然后更新
		 */
		Test1 test1=test1Dao.get("253ca3bc-6dc9-48a5-9948-067a40394497");
		test1.getTest2().remove(test2Dao.get("c99c5a0d-6574-499a-ba59-e677afc1b8bf"));
		test1Dao.update(test1);
		
	}
	@Override
	public void delete() {
		/**
		 * 删除维护关系的Test1,如果在关联表中有相关的记录,也会删除
		 */
		test1Dao.delete(test1Dao.get("253ca3bc-6dc9-48a5-9948-067a40394497"));
		
		/**
		 * 如果需要删除Test2中的a记录,需要先找出Test2中a记录关联的Test1的记录列表,
		 * 然后通过Test1的那些记录逐个remove掉关联表中关于a的记录,然后更新Test1
		 * 最后再在Test2中删除a记录
		 */
		//test2Dao.delete(test2Dao.get("c99c5a0d-6574-499a-ba59-e677afc1b8bf"));
	}
 

对于被维护端删除操作烦琐的问题需要解决。两端均维护关系?

 

比较习惯将manytomany拆分成两个manytoone。 

 

 

Hibernate manytomany

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