mybatis快速入门

朱雀 2022-07-13 01:37 307阅读 0赞

## Mybatis简介 ##

MyBatis是支持普通SQL查询，存储过程和高级映射的优秀持久层框架。MyBatis消除了几乎所有的JDBC代码和参数的手工设置以及对结果集的检索封装。MyBatis可以使用简单的XML或注解用于配置和原始映射，将接口和Java的POJO（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录。

## Mybatis快速入门 ##

下面写一个简单的测试例子，首先新建一个project，导入mybatis核心jar包和mysql驱动jar包：  
![image\_1b4adm56plbu1d1bgvv8p21fdu9.png-4.6kB][image_1b4adm56plbu1d1bgvv8p21fdu9.png-4.6kB]

新建数据库和表，并插入两条记录：

create database mybatis;
    use mybatis;
    CREATE TABLE users(id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20), age INT);
    INSERT INTO users(NAME, age) VALUES('Tom', 12);
    INSERT INTO users(NAME, age) VALUES('Jack', 11);

建表成功：  
![image\_1b4aeseal1l64lvmiht1b391ns913.png-14kB][image_1b4aeseal1l64lvmiht1b391ns913.png-14kB]

新建实体类User.java

package com.mybatis.entities;
    
    public class User { 
        private Integer id;
        private String name;
        private Integer age;
    
        //getters and setters
    
        @Override
        public String toString() {
            return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
        }
    
    }

新建实体类的映射文件userMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> 
    <mapper namespace="com.mybatis.entities.userMapper"> 
        
        
        
        <select id="getUser" parameterType="int" resultType="com.mybatis.entities.User">
            select * from users where id=#{id}
        </select>
    </mapper>

在src目录下新建mybatis配置文件conf.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/mybatis" />
                    <property name="username" value="你的数据库用户名" />
                    <property name="password" value="你的数据库密码" />
                </dataSource>
    
            </environment>
        </environments>
    
        
        <mappers>
        <mapper resource="com/mybatis/entities/userMapper.xml"/>
        </mappers>
    </configuration>

测试：

public class Test { 
    
        @org.junit.Test
        public void test() {
            //读取配置文件
            String resource = "conf.xml";
            InputStream is = this.getClass().getClassLoader().getResourceAsStream(resource);
    
            //创建SqlSessionFactory和SqlSession
            SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
            SqlSession session = sessionFactory.openSession();
    
            //映射sql的标识字符串
            //com.mybatis.entities.userMapper对应映射文件中的namespace
            //getUser对应映射文件中的select标签的id
            String statement = "com.mybatis.entities.userMapper"+".getUser";
            //执行查询返回id为1的记录
            User user = session.selectOne(statement, 1);
            System.out.println(user);
        }
    }

运行结果如下图所示：  
![image\_1b4agku565uour7v9ub851m4q1g.png-5.2kB][image_1b4agku565uour7v9ub851m4q1g.png-5.2kB]

[image_1b4adm56plbu1d1bgvv8p21fdu9.png-4.6kB]: /images/20220713/d9cae6e0c8914614992c4230233a3836.png
[image_1b4aeseal1l64lvmiht1b391ns913.png-14kB]: /images/20220713/f1a8b53640bb4d3eb67125a03b3006f0.png
[image_1b4agku565uour7v9ub851m4q1g.png-5.2kB]: /images/20220713/5fb50e59f8eb46b1b60dd184e1e737f4.png