ORMapping

第一种：一对一单向外键关联

一、Annotaion配置

小实验1:

(1)编写hunsband.java，属性为id,name,wife。id是主键

(2)编写wife.java，属性为id,name。id是主键

(3)实现方式：在husband.java中，用wife作为外键关联wife.java中的主键id

Husband.java

package com.zgy.hibernate.model;



import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.OneToOne;



@Entity

public class Husband {

private int id;

private String name;

private Wife wife;

@Id

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;

}

@OneToOne

@JoinColumn(name="wifeId")

public Wife getWife() {

return wife;

}

public void setWife(Wife wife) {

this.wife = wife;

}



}





Wife.java

package com.zgy.hibernate.model;



import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;



@Entity

public class Wife {

private int id;

private String name;

@Id

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;

}





}

Junit测试

package com.zgy.hibernate.model;



import static org.junit.Assert.*;



import java.util.Date;



import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.AnnotationConfiguration;

import org.junit.AfterClass;

import org.junit.BeforeClass;

import org.junit.Test;



public class ORMapppingTest {



public static SessionFactory sf = null;

@BeforeClass

public static void beforeClass(){

sf = new AnnotationConfiguration().configure().buildSessionFactory();

}

@Test

public void test() {

Husband h = new Husband();

Wife w = new Wife();







Session session2 = sf.openSession();

session2.beginTransaction();

w.setId(1);

w.setName("李四");

session2.save(w);

session2.getTransaction().commit();



Session session1 = sf.openSession();

session1.beginTransaction();

h.setId(1);

h.setName("张三");

h.setWife(w);

session1.save(h);

session1.getTransaction().commit();

}



@AfterClass

public static void afterClass(){

sf.close();

}



}

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观察结果：

1、观察hibernate生成的sql语句：

Hibernate: create table Husband (id integer not null, name varchar(255), wifeId integer, primary key (id))

Hibernate: create table Wife (id integer not null, name varchar(255), primary key (id))

Hibernate: alter table Husband add constraint FK_kruq9jfxa0jrc2od8dbh09mia foreign key (wifeId) references Wife (id)

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2、如果不加@JoinColumn(name="wifeId"),在husband表将增加了关联wife表主键的外键wife_id。

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3、使用sql语句：show create table husband;可以看到如下sql语句