hibernate一对一的单向和双向关系

单向和双向的区别
单向的意思：保存的关系维护者，做的任何操作，都会影响，另外一个实体。
操作包含 4种增加删除修改查询

双向的意思：可以随便通过一方去操作另外一方

@Data get 和set 方法重写hashcode 和equals方法重写toString方法

如：

mouth类是关系非维护者

Person2是关系维护者

单向关联：
如：在关系维护端添加
@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "mid",nullable = false,unique = true)
private Mouth mouth;
双向关系：
1.重写toString方法 toString只要有基本数据类型即可
2.在关系维护端(有外键的实体) One2One() 取消该nullabled
如：在关系维护端添加
@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "mid",unique = true)
private Mouth mouth;
在非关系维护端：
@OneToOne(mappedBy = "mouth",cascade = CascadeType.ALL)
private Person2 person;

A.所谓双向相关在非关系维护端添加@OneToOne的主键
定义一个属性mappedby（被映射）
mappedby里面写的是当前该属性的返回值类型的外键关联属性
@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "mid",unique = true)
private Mouth mouth;
在非关系维护端：
@OneToOne(mappedBy = "mouth",cascade = CascadeType.ALL)
private Person2 person;

B.mappedby的意思就是表示我不维护关系由你定义的这个属性来维护关系
(mappedby="Person.mouth") person.mouth 由Person类的mouth属性来维护
C.既然不维护关系所以在新增数据的数据如果你当前新增的数据是非关系维护端
不维护关系所以在做级联操作的时候，而只会保存数据，不会建立关系，

注：无论在单向还是双向必须保存关系维护端才会建立关联关系

例子：双向外键关联-保存关系维护端

mouth类是关系非维护者

Person2是关系维护者

package com.oracle.bean2;

import lombok.Data;
import org.hibernate.annotations.GenericGenerator;

import javax.persistence.*;

@Data
@Entity
public class Person2 {
    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid",strategy = "uuid")
    private String pid;
    private String pname;
    @OneToOne(cascade = CascadeType.ALL)
    //@JoinColumn(name = "mid",nullable = false,unique = true)
    @JoinColumn(name = "mid",unique = true)
    private Mouth mouth;
    @Override
    public String toString() {
        return "Person2{" +
                "pid='" + pid + '\'' +
                ", pname='" + pname + '\'' +
                '}';
    }
}

package com.oracle.bean2;

import lombok.Data;
import org.hibernate.annotations.GenericGenerator;

import javax.persistence.*;
//@Data  get 和set 方法 重写hashcode 和equals方法 重写toString方法
@Entity
@Data
public class Mouth {
    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid",strategy = "uuid")
    private String mid;
    private String color;
    private String type;
    @OneToOne(mappedBy = "mouth",cascade = CascadeType.ALL)
    private Person2 person;
    @Override
    public String toString() {
        return "Mouth{" +
                "mid='" + mid + '\'' +
                ", color='" + color + '\'' +
                ", type='" + type + '\'' +
                '}';
    }
}

保存维护关系的增删查改

hibernate一对一的单向和双向关系

package com.oracle.core;

import com.oracle.bean2.Mouth;
import com.oracle.bean2.Person2;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class One2oneTest {

    private SessionFactory sessionFactory;
    private Session session;

    @Before
    public void begin(){
        org.hibernate.cfg.Configuration cfg=new org.hibernate.cfg.Configuration();
        cfg.configure();
        sessionFactory = cfg.buildSessionFactory();
        session = sessionFactory.openSession();
        session.beginTransaction();
    }

    //增加
   @Test
    public void one2onesave(){
      Person2 person=new Person2();
      person.setPname("糖宝");
        Mouth mouth=new Mouth();
        mouth.setColor("红色");
        mouth.setType("小");
      person.setMouth(mouth);
      session.save(person);



    }
   
    @Test
    public void delete(){
        Mouth mouth = session.get(Mouth.class, "8a8aac9463859f500163859f54070001");
        session.delete(mouth);

    }
    //修改
    @Test
    public void update(){
        Mouth mouth = session.get(Mouth.class, "8a8aac9463859f500163859f54070001");
       mouth.getPerson().setPname("小妖王");
       session.update(mouth);

    }
    //查询
    @Test
    public void query(){
        Mouth mouth = session.get(Mouth.class, "8a8aac9463859f500163859f54070001");
        System.out.println(mouth.getPerson());

    }

    @After
    public void end(){
        session.getTransaction().commit();
        session.close();
        sessionFactory.close();
    }


}

保存非维护关系的

hibernate一对一的单向和双向关系

package com.oracle.core;

import com.oracle.bean2.Mouth;
import com.oracle.bean2.Person2;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class One2oneTest2 {

    private SessionFactory sessionFactory;
    private Session session;

    @Before
    public void begin(){
        org.hibernate.cfg.Configuration cfg=new org.hibernate.cfg.Configuration();
        cfg.configure();
        sessionFactory = cfg.buildSessionFactory();
        session = sessionFactory.openSession();
        session.beginTransaction();
    }
   @Test
    public void one2one2(){
        Person2 person=new Person2();
       person.setPname("妖王");
        Mouth mouth=new Mouth();
        mouth.setColor("红色");
        mouth.setType("大");
        mouth.setPerson(person);
       session.save(mouth);
    }
    
    @After
    public void end(){
        session.getTransaction().commit();
        session.close();
        sessionFactory.close();
    }


}

hibernate一对一的单向和双向关系

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