项目图片



hibernate.cfg.xml

<mapping resource="com/jege/hibernate/one/way/manytoone/User.hbm.xml" />

        <mapping resource="com/jege/hibernate/one/way/manytoone/Dept.hbm.xml" />

映射文件

User.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.jege.hibernate.one.way.manytoone">

    <class name="User" table="t_user">

        <id name="id">

            <generator class="native" />

        </id>

        <property name="username" column="name" />

        <!-- class属性:配置一方的全限定类名或者类名，也可以不用配置,Hibernate可以通过反射获取 -->

        <!-- column属性：配置外键，对应于一方Dept的主键id，也可以不配置默认用属性名称name=dept作为多方的外键列名 -->

        <many-to-one name="dept" class="Dept" column="dept_id" />

    </class>

</hibernate-mapping>

Dept.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.jege.hibernate.one.way.manytoone">

    <class name="Dept" table="t_dept">

        <id name="id">

            <generator class="native" />

        </id>

        <property name="name" />

    </class>

</hibernate-mapping>

CrudTest

package com.jege.hibernate.one.way.manytoone;

import org.hibernate.Session;

import org.junit.Before;

import org.junit.Test;

import com.jege.hibernate.util.HibernateUtils;

/**

 * @author JE哥

 * @email 1272434821@qq.com

 * @description:单向多对一的处理

 */

public class CrudTest {

  // 单个保存:一次性保存1个部门，保存3个员工

  // 在单向多对一保存的时候需要先保存一方，不是会出现多余的update语句，影响性能

  @Before

  public void before() throws Exception {

    Dept dept = new Dept();

    dept.setName("部门1");

    // 传入dept的本质是处理数据库user表的dept_id外键

    User user1 = new User("员工1", dept);

    User user2 = new User("员工2", dept);

    Session session = HibernateUtils.INSTANCE.getSession();

    session.beginTransaction();

    System.out.println("保存之前：" + dept);

    session.save(dept);// Hibernate会自动把保存后的主键放到当前对象的id里面

    System.out.println("保存之后：" + dept);

    session.save(user1);

    session.save(user2);

    session.getTransaction().commit();

    session.close();

  }

  @Test

  public void save() throws Exception {

  }

  @Test

  public void update() throws Exception {

    Session session = HibernateUtils.INSTANCE.getSession();

    User user = (User) session.get(User.class, 1L);

    user.setUsername("jege");

    session.beginTransaction();

    session.update(user);

    session.getTransaction().commit();

    session.close();

  }

  @Test

  public void delete() throws Exception {

    Session session = HibernateUtils.INSTANCE.getSession();

    User user = (User) session.get(User.class, 1L);

    session.beginTransaction();

    session.delete(user);

    session.getTransaction().commit();

    session.close();

  }

  @Test

  public void get() throws Exception {

    Session session = HibernateUtils.INSTANCE.getSession();

    User user = (User) session.get(User.class, 1L);

    System.out.println(user);

    System.out.println(user.getDept());

  }

}

源码地址

https://github.com/je-ge/hibernate

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