1. MyBatis 简介

Posted 2020-09-13

1. 传统 JDBC 编程

 

2. ORM 模型

Object Relational Model，对象映射模型：数据库的表和 POJO （Plain Ordinary Java Object） 的映射关系模型。

 

3. Hibernate

全表映射；不能组装 SQL；对多表关联和复杂 SQL 查询支持较差；性能较差。

 

4. MyBatis

半自动映射框架：手工匹配提供 POJO、SQL 和映射关系。

 

5. 什么时候用 MyBatis

 

mybais-helloworld

 

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/test"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com\\sunyard\\dao\\xml\\UserMapper.xml"/>
    </mappers>
</configuration>

 

User.java

package com.sunyard.model;

import java.util.Date;

/**
 * Created by gaoeb on 2017/4/24.
 */
public class User {
    private int id;
    private String username;
    private String password;
    private int credits;
    private String lastIp;
    private Date lastVisit;
    private Date createTime;
    private Date updateTime;
    private int status;

    // getter and setter
}

 

UserMapper.java

package com.sunyard.dao;

import com.sunyard.model.User;

/**
 * Created by gaoeb on 2017/4/24.
 */
public interface UserMapper {
    User getUserById(int id);
}

 

UserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.sunyard.dao.UserMapper">

    <select id="getUserById" parameterType="java.lang.Integer" resultType="com.sunyard.model.User">
        SELECT
            id          AS id,
            username    AS username,
            password    AS password,
            credits     AS credits,
            last_ip     AS lastIp,
            last_visit  AS lastVisit,
            create_time AS createTime,
            update_time AS updateTime,
            status      AS status
        FROM t_user
        WHERE id = #{id}
    </select>

</mapper>

 

MyBatisUtil.java

package com.sunyard.util;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;

/**
 * Created by gaoeb on 2017/4/24.
 */
public class MyBatisUtil {

    private static SqlSessionFactory sqlSessionFactory = null;

    public static SqlSessionFactory getSessionFactory() {
        if (sqlSessionFactory == null) {
            try {
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
                return sqlSessionFactory;
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return sqlSessionFactory;
    }

}

 

Main.java

import com.sunyard.dao.UserMapper;
import com.sunyard.model.User;
import com.sunyard.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;

public class Main {

    public static void main(String[] args) {
        System.out.println("Hello World!");
        SqlSession session = MyBatisUtil.getSessionFactory().openSession();
        UserMapper userMapper = session.getMapper(UserMapper.class);
        User user = userMapper.getUserById(1);
        System.out.println(user.toString());
        session.close();
    }
}

 

 

 

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