Mybatis官方文档：

https://mybatis.org/mybatis-3/zh/index.html

1. 为什么需要MyBatis

  • 帮助程序员将数据存入到数据库中

  • 方便

  • 传统的JDBC代码太复杂了，简化，框架，自动化

  • 不用MyBatis也可以，技术没有高低之分

  • 优点：

    • 简单易学
    • 灵活
    • sql和代码的分离，提高了可维护性。
    • 提供映射标签，支持对象与数据库的orm字段关系映射
    • 提供对象关系映射标签，支持对象关系组建维护
    • 提供xml标签，支持编写动态sql

2、第一个Mybatis程序

思路：搭建环境 –> 导入MyBatis –> 编写代码 –> 测试

.2.1导入maven依赖配置

<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.5</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.21</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.13</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.12</version>
    </dependency>
</dependencies>
<build>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

2.2目录结构

image.png

2.3mybatis-config配置

<?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核心配置文件-->
<configuration>
    <properties resource="db-config.properties"/>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/UserDao.xml" />
    </mappers>
</configuration>

注意点:这里url的value需要使用${jdbc.url}否则在编译的时候回出现错误，value值回自动替换成www.example.com

2.4 db-config.properties配置

====

2.5 编写mybatisUtil工具类

package com.zhangpan.utils;
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.apache.ibatis.session.SqlSessionManager;
import java.io.IOException;
import java.io.InputStream;
public class MybatisUtil {
    static SqlSessionFactory sqlSessionFactory = null;
    static {
        try {
            String MybatisConfig = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(MybatisConfig);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

2.6编写dao接口

package com.zhangpan.mapper;
import com.zhangpan.pojo.User;
import java.util.List;
public interface UserDao {
    public List<User> getUserList();
    public void addUser(User user);
}

2.7编写接口实现UserDao.xml(由原来的接口实现类变成xml配置文件)

<?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">
<!--namespace=绑定一个指定的Dao/Mapper接口-->
<mapper namespace="com.zhangpan.mapper.UserDao">
    <select id="getUserList" resultType="com.zhangpan.pojo.User">
    select * from USER
  </select>
    <select id="addUser" parameterType="com.zhangpan.pojo.User">
        insert into USER (username,sex,birthday,address) value (#{username},#{sex},#{birthday},#{address})
    </select>
</mapper>

2.8 Junit测试

package com.zhangpan;
import com.zhangpan.mapper.UserDao;
import com.zhangpan.pojo.User;
import com.zhangpan.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.Date;
import java.util.List;
public class test {
    @Test
    public void test1(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        List<User> userList = userDao.getUserList();
        for (User user:userList){
            System.out.println(user);
        }
        sqlSession.close();
    }
    @Test
    public void addUser_test(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        UserDao userDao = sqlSession.getMapper(UserDao.class);
        User user = new User();
        user.setUsername("关二爷");
        user.setSex("1");
        user.setBirthday(new Date());
        user.setAddress("光棍屯18号");
        userDao.addUser(user);
        sqlSession.commit();
        sqlSession.close();
    }
}

未完待续。。。