1. 开发流程

• a. 创建实体类

package com.fuyi.entity;

import java.util.Date;

public class User {
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    // 此处省略getter和setter
}

• b. 引入Mybatis、Mysql和Juint依赖

<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.2</version>
    </dependency>

    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.47</version>
    </dependency>
</dependencies>

• c. 配置映射配置文件

<?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">
<mapper namespace="UserMapper">
    <!--查询所有-->
    <select id="findAll" resultType="com.fuyi.entity.User">
        select * from user
    </select>
</mapper>

命名空间（namespace），它的作用主要是利用namespace+id的方式进而确定唯一的语句映射关系

• d. 配置SqlMapConfig.xml核心配置文件

<?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>
    <!--环境配置-->
    <environments default="development">
        <!--使用MySQL环境-->
        <environment id="development">
            <!--使用JDBC类型事务管理器-->
            <transactionManager type="JDBC"></transactionManager>
            <!--使用连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"></property>
                <property name="url" value="jdbc:mysql:///mybatis_db"></property>
                <property name="username" value="root"></property>
                <property name="password" value="123456"></property>
            </dataSource>
        </environment>
    </environments>
    <!--加载映射配置-->
    <mappers>
        <mapper resource="mapper/UserMapper.xml"></mapper>
    </mappers>
</configuration>

• e. 编写测试类

@Test
public void test() throws IOException {

    // 1. 加载核心配置文件
    InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");

    // 2. 获取SQLFactory工厂对象
    SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(resourceAsStream);

    // 3. 获取SQLSession对象
    SqlSession sqlSession = factory.openSession();

    // 4. 执行SQL参数
    List<User> result = sqlSession.selectList("UserMapper.findAll");

    // 5. 打印结果
    result.forEach(System.out::println);

    // 6. 释放资源
    sqlSession.close();

}

2. 增删查改（CURD）

2.1 增加操作

<!-- 新增 -->
<insert id="save" parameterType="com.fuyi.entity.User">
    insert into user (username, birthday, sex, address)
    value (#{username}, #{birthday}, #{sex}, #{address})
</insert>

• parameterType表示传入的参数类型
• Sql语句中使用#{实体属性名}方式引用实体中的属性值

@Test
public void saveTest() throws IOException {
    // 1. 加载核心配置文件
    InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");

    // 2. 获取SQLFactory工厂对象
    SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(resourceAsStream);

    // 3. 获取SQLSession对象
    SqlSession sqlSession = factory.openSession();

    // 4. 创建user实体对象
    User user = new User();
    user.setUsername("Lucy");
    user.setBirthday(new Date());
    user.setSex("女");
    user.setAddress("广东广州");

    // 5. 执行SQL参数
    int insert = sqlSession.insert("UserMapper.save", user);
    System.out.println(insert);

    // 6. 提交事务
    sqlSession.commit();

    // 7. 释放资源
    sqlSession.close();
}

2.2 更新操作

<!-- 修改 -->
<update id="updateById" parameterType="com.fuyi.entity.User">
    update user
    set
    username = #{username},
    birthday = #{birthday},
    sex = #{sex},
    address = #{address}
    where id = #{id}
</update>

@Test
public void updateTest() throws IOException {
    // 1. 加载核心配置文件
    InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");

    // 2. 获取SQLFactory工厂对象
    SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(resourceAsStream);

    // 3. 获取SQLSession对象
    SqlSession sqlSession = factory.openSession();

    // 4. 创建user实体对象
    User user = new User();
    user.setId(5);
    user.setUsername("Lucy");
    user.setBirthday(new Date());
    user.setSex("女");
    user.setAddress("广东肇庆");

    // 5. 执行SQL参数
    int update = sqlSession.update("UserMapper.updateById", user);
    System.out.println(update);

    // 6. 提交事务
    sqlSession.commit();

    // 7. 释放资源
    sqlSession.close();
}

2.3 删除操作

<!-- 删除 -->
<delete id="deleteById" parameterType="java.lang.Integer">
    delete from user where id = #{id}
</delete>

在这里，SQL语句可以使用#{任意字符串}方式引用传递的单个参数

@Test
public void deleteTest() throws IOException {
    // 1. 加载核心配置文件
    InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");

    // 2. 获取SQLFactory工厂对象
    SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(resourceAsStream);

    // 3. 获取SQLSession对象
    SqlSession sqlSession = factory.openSession();

    // 4. 执行SQL参数
    int delete = sqlSession.delete("UserMapper.deleteById", 5);
    System.out.println(delete);

    // 5. 提交事务
    sqlSession.commit();

    // 6. 释放资源
    sqlSession.close();
}