2021-5-13讲课内容hibernate主键id映射_XML方式

目录

• • 概述
  • • 项目结构
    • • Student类
      • hibernate.cfg.xml
      • log4j.properties
      • Student.hbm.xml
      • StudentTest类
  • 理论
  • • 常用的五种方式
    • • 1. increment：
      • 2. identity主键自增
      • 3.sequence 序列
      • 4. native
      • 5. uuid

概述

代码和博客 略有不同，但是大体上是一样的

项目结构

Student类

package cn.edu.ldu.entity;

public class Student {
    // private int id;
    private String id;
    private String name;
    //必须要有一个无参的构造方法
    //如果写了一个有参构造，必须要有一个午餐的构造方法写出来
    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD//EN"
    "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="url">
      jdbc:mysql://localhost:3306/hibernate?characterEncoding=utf-8&amp;useSSL=false&amp;serverTimezone=UTC
    </property>
<!--    ?characterEncoding=utf-8&useSSL=false&serverTimezone=UTC-->
    <property name="driverClassName"> com.mysql.cj.jdbc.Driver </property>
    <property name="username">root</property><!--connection.-->
    <property name="password">123456</property>
    <!-- DB schema will be updated if needed -->
    <property name="connection.provider_class">
      com.alibaba.druid.support.hibernate.DruidConnectionProvider </property>
    <property name="filters">stat</property>
    <property name="hibernate.current_session_context_class">thread</property>
    <property name="show_sql">true</property>
    <property name="format_sql">true</property>
    <property name="hbm2ddl.auto">create</property>
    <property name="hibernate.hibernate.hbm2ddl.auto">update</property>
    <!--    进行修改-->
    <property name="hibernate.dialect">org.hibernate.dialect.MySQL8Dialect</property>
<!--    加入映射-->
    <mapping resource="Student.hbm.xml"></mapping>
  </session-factory>
</hibernate-configuration>

log4j.properties

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD//EN"
    "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="url">
      jdbc:mysql://localhost:3306/hibernate?characterEncoding=utf-8&amp;useSSL=false&amp;serverTimezone=UTC
    </property>
<!--    ?characterEncoding=utf-8&useSSL=false&serverTimezone=UTC-->
    <property name="driverClassName"> com.mysql.cj.jdbc.Driver </property>
    <property name="username">root</property><!--connection.-->
    <property name="password">123456</property>
    <!-- DB schema will be updated if needed -->
    <property name="connection.provider_class">
      com.alibaba.druid.support.hibernate.DruidConnectionProvider </property>
    <property name="filters">stat</property>
    <property name="hibernate.current_session_context_class">thread</property>
    <property name="show_sql">true</property>
    <property name="format_sql">true</property>
    <property name="hbm2ddl.auto">create</property>
    <property name="hibernate.hibernate.hbm2ddl.auto">update</property>
    <!--    进行修改-->
    <property name="hibernate.dialect">org.hibernate.dialect.MySQL8Dialect</property>
<!--    加入映射-->
    <mapping resource="Student.hbm.xml"></mapping>
  </session-factory>
</hibernate-configuration>

Student.hbm.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD//EN"
    "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="url">
      jdbc:mysql://localhost:3306/hibernate?characterEncoding=utf-8&amp;useSSL=false&amp;serverTimezone=UTC
    </property>
<!--    ?characterEncoding=utf-8&useSSL=false&serverTimezone=UTC-->
    <property name="driverClassName"> com.mysql.cj.jdbc.Driver </property>
    <property name="username">root</property><!--connection.-->
    <property name="password">123456</property>
    <!-- DB schema will be updated if needed -->
    <property name="connection.provider_class">
      com.alibaba.druid.support.hibernate.DruidConnectionProvider </property>
    <property name="filters">stat</property>
    <property name="hibernate.current_session_context_class">thread</property>
    <property name="show_sql">true</property>
    <property name="format_sql">true</property>
    <property name="hbm2ddl.auto">create</property>
    <property name="hibernate.hibernate.hbm2ddl.auto">update</property>
    <!--    进行修改-->
    <property name="hibernate.dialect">org.hibernate.dialect.MySQL8Dialect</property>
<!--    加入映射-->
    <mapping resource="Student.hbm.xml"></mapping>
  </session-factory>
</hibernate-configuration>

StudentTest类

package cn.edu.ldu.entity;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.After;
import org.junit.Before;
import org.junit.jupiter.api.Test;

public class StudentTest {
    public static void main(String[] args) {
        Configuration config = new Configuration().configure("/hibernate.cfg.xml");
        SessionFactory sessionFactory = config.buildSessionFactory();
        Session session = sessionFactory.openSession();
        Student student = new Student();
        student.setName("PushyTao");
        session.beginTransaction(); //完整性一致性
        session.save(student);
        session.getTransaction().commit(); //提交
        session.close();
        sessionFactory.close();
    }
    /*@Before
    public void testJunit(){
        System.out.println("before");
    }
    @Test
    public void testInsert(){
        System.out.println("test the insert");
    }
    @After
    public void testUpdate(){
        System.out.println("after");
    }*/

}

理论

常用的五种方式

1. increment：

2. identity主键自增

3.sequence 序列

4. native

5. uuid