MyBatis专栏1 - 入门

代码实例: 使用MyBatis实现user表的增删改查CRUD

准备

创建数据库表

#创建数据库
create database mybatis_demo;
#创建user表
create table user(
	uid int primary key auto_increment,
    username varchar(40),
    sex varchar(10),
    birthday date,
    address varchar(40)
);

创建Maven工程

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
    
    <!--引入lombok的依赖-->
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.18.10</version>
    </dependency>
    
    <!--mysql驱动-->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.47</version>
    </dependency>
    
    <!--mybatis的依赖-->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.3</version>
    </dependency>
</dependencies>

创建Mybatis快速入门

1.创建POJO类

package com.nengli51.pojo;

import lombok.Data;

import java.util.Date;

/**
 * @Date 2021/2/4
 */
@Data
public class User {
    
    

    private int uid;
    private String username;
    private String sex;
    private Date birthday;
    private String address;
}

2. 创建UserDao

package com.nengli51.dao;

import com.nengli51.pojo.User;

import java.util.List;

public interface UserDao {
    
    
    /**
     * 添加用户
     *
     * @param user
     */
    void addUser(User user);

    /**
     * 删除用户
     *
     * @param uid
     */
    void deleteUser(int uid);

    /**
     * 修改用户
     *
     * @param user
     */
    void updateUser(User user);

    /**
     * 查找用户
     *
     * @param uid
     * @return
     */
    User findUser(int uid);

    /**
     * 查找所有
     *
     * @return
     */
    List<User> findAll();
}

3. 创建UserDao.xml映射文件

注意: 放置在resources/“UserDao相同的路径下”/UserDao.xml

这里的"UserDao相同的路径下" = 上面的UserDao接口的位置: com/nengli51/dao/下面

<?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.nengli51.dao.UserDao">
    <select id="findUser" resultType="com.nengli51.pojo.User" parameterType="int">
        select *
        from user
        where uid = #{id};
    </select>
    <select id="findAll" resultType="com.nengli51.pojo.User">
        select *
        from user
    </select>

    <insert id="addUser" parameterType="com.nengli51.pojo.User">
        insert into user
        values (null, #{username}, #{sex}, #{birthday}, #{address})
    </insert>

    <delete id="deleteUser" parameterType="int">
        delete
        from user
        where uid = #{uid}
    </delete>

    <update id="updateUser" parameterType="com.nengli51.pojo.User">
        update user
        set username=#{username},
            sex=#{sex},
            birthday=#{birthday},
            address=#{address}
        where uid = #{uid}
    </update>
</mapper>

4. 创建SqlMapConfig.xml核心配置文件

放置在: resources/目录下

<?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="dev">
        <environment id="dev">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/nengli51/UserDao.xml"></mapper>
    </mappers>
</configuration>

5. 测试CRUD

import com.nengli51.dao.UserDao;
import com.nengli51.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.List;

/**
 * @Author MaLi
 * @Date 2021/2/4
 */
public class TestMybatis {
    
    

    private UserDao userDao;
    private SqlSession sqlSession;
    private InputStream is;

    @Before
    public void init() {
    
    
        try {
    
    
            //1. 创建SqlSessionFactoryBuilder对象
            SqlSessionFactoryBuilder sessionFactoryBuilder = new SqlSessionFactoryBuilder();

            //2. 读取核心配置文件，转换成字节输入流
            is = Resources.getResourceAsStream("SqlMapConfig.xml");

            //3. 创建SqlSessionFactory对象
            SqlSessionFactory sessionFactory = sessionFactoryBuilder.build(is);

            //4. 创建SqlSession对象
            sqlSession = sessionFactory.openSession();

            //5. 创建UserDao的代理对象
            userDao = sqlSession.getMapper(UserDao.class);

        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
    }

    @Test
    public void testAddUser() {
    
    
        User user = new User();
        user.setUsername("小马哥");
        user.setAddress("Beijing");
        user.setBirthday(new Date());
        user.setSex("Male");
        userDao.addUser(user);
        user = userDao.findUser(4);
        System.out.println(user);
    }

    @Test
    public void testDeleteUser() {
    
    
        userDao.deleteUser(1);
    }

    @Test
    public void testUpdateUser() {
    
    
        User user = userDao.findUser(1);
        user.setUsername("马斯克");
        userDao.updateUser(user);
        user = userDao.findUser(1);
        System.out.println(user);
    }

    @Test
    public void testFindUser() {
    
    
        User user = userDao.findUser(1);
        System.out.println(user);
    }

    @Test
    public void testFindAll() {
    
    
        List<User> userList = userDao.findAll();
        //6, 使用UserDao进行操作
        for (User user : userList) {
    
    
            System.out.println(user);
        }

    }

    @After
    public void destroy() throws IOException {
    
    
        //7.提交事务, 关闭资源
        sqlSession.commit();
        sqlSession.close();
        is.close();
    }
}