hibernate oneTOmany 单向

最新推荐文章于 2020-04-23 11:16:21 发布

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本文介绍了如何使用Hibernate ORM框架在Java应用中实现Group_t实体类与Member实体类的一对多单向关系设置，通过设置cascade类型为ALL并在Member实体类中加入group_id列，确保数据的一致性和完整性。示例代码展示了具体实现过程及数据库操作。

Hibernate one to many 单向设置：

实体类：

Group_t

package com.sshcp.model;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;

@Entity
public class Group_t {
	
	private int id ;
	private String name;
	private Set<Member> members = new HashSet<Member>();
	
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
	@OneToMany(cascade=CascadeType.ALL)
	@JoinColumn(name="group_id") // 此处要加joincolumn 否则会生成第三张表
	public Set<Member> getMembers() {
		return members;
	}
	public void setMembers(Set<Member> members) {
		this.members = members;
	}
	
	

}

Member.java

package com.sshcp.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class Member {
	
	private int id ;
	private String name ;
	
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	

}

设置类：

public void saveOnetoManySingle() {
		// TODO Auto-generated method stub
		
		Group_t gt = new Group_t();
		Member member1 = new Member();
		Member member2 = new Member();
		
		gt.setName("组一");
		member1.setName("成员一");
		member2.setName("成员二");
		
		gt.getMembers().add(member1);
		gt.getMembers().add(member2);
		
		this.getHibernateTemplate().save(gt);
		
	}

代码运行结果：

Hibernate: insert into Group_t (name) values (?)
Hibernate: insert into Member (name) values (?)
Hibernate: insert into Member (name) values (?)
Hibernate: update Member set group_id=? where id=?
Hibernate: update Member set group_id=? where id=?