1. 第一个Mybatis程序

1.1 搭建数据库

DROP DATABASE IF  EXISTS `mybatis`;
CREATE DATABASE IF NOT EXISTS `mybatis`;
USE `mybatis`;
DROP DATABASE IF EXISTS `user`;
CREATE TABLE `user`(
    `id` INT(20) NOT NULL,
    `name` VARCHAR(20) DEFAULT NULL,
    `pwd` VARCHAR(32) DEFAULT NULL,
    PRIMARY KEY(`id`)
)ENGINE=INNODB DEFAULT CHARSET=utf8;
INSERT INTO `user` (`id`,`name`,`pwd`) 
VALUES (1,'张三',MD5('123456')),
        (2,'李四' ,MD5('111')),
        (3,'王五',MD5('222'));

1.2 添加maven依赖

<dependencies>
  <dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.7</version>
  </dependency>
  <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.11</version>
    <scope>test</scope>
  </dependency>
  <dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.22</version>
  </dependency>
  <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.27</version>
  </dependency>
</dependencies>

1.3 配置mybatis文件

<?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.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
</configuration>

1.4 定义实体类

import lombok.Data;
@Data
public class User {
    private int id;
    private String name;
    private String pwd;
}

1.5 编写工具类

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 java.io.IOException;
import java.io.InputStream;
// sqlSessionFactory --> sqlSession
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String resources = "mybatis-config.xml";
        try {
            InputStream inputStream = Resources.getResourceAsStream(resources);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

1.6 定义dao接口

import java.util.List;
public interface UserDao {
    List<User> getUserList();
}

1.7 编写mapper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">
<!--绑定对应的dao接口-->
<mapper namespace="com.lu.dao.UserDao">
    <!--select查询语句-->
    <!--id对应方法名-->
    <!--resultType 返回值类型-->
    <select id="getUserList" resultType="com.lu.entity.User">
        select *
        from user;
    </select>
</mapper>

• namespace一定要正确绑定到dao上
• id 就是 dao中的方法
• resultType sql语句执行返回值类型
• parameterType 传递参数类型

1.8 注册mapper到配置文件中

<?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.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="lzf990507"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/lu/dao/UserMapper.xml"/>
    </mappers>
</configuration>

1.9 配置maven过滤

<resources>
    <resource>
        <directory>src/main/resources</directory>
        <includes>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
        </includes>
        <filtering>true</filtering>
    </resource>
    <resource>
        <directory>src/main/java</directory>
        <includes>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
        </includes>
        <filtering>true</filtering>
    </resource>
</resources>

1.10 测试

import com.lu.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
public class UserDaoTest {
    @Test
    public void test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.getUserList().forEach(System.out::println);
    }
}

User(id=1, name=张三, pwd=e10adc3949ba59abbe56e057f20f883e)
User(id=2, name=李四, pwd=698d51a19d8a121ce581499d7b701668)
User(id=3, name=王五, pwd=bcbe3365e6ac95ea2c0343a2395834dd)