上一篇完成了MyBatis环境的搭建及第一个MyBatis程序的编写第一个MyBatis程序，现在在此基础上，实现数据库的增删改查
以下的操作，均只需要修改接口UserMapper及xml配置文件UserMapper.xml即可
值得一提的是，如果idea连接了数据库，下面的mapper文件写SQL语句的时候有代码提示

一、SELECT，查操作

接口加入一个查询方法，通过User的id查询

User getUserById(Integer id);

UserMapper.xml在命名空间为UserMapper的mapper下，添加一个select模块

<select id="getUserById" resultType="com.du.mybatis.pojo.User" parameterType="int">
    select id, `name`, address
    from user
    where id = #{id};
</select>

id 为对应方法名，resultType为返回的参数类型，parameterType为方法输入参数类型
输入参数通过#{id}获得
测试方法

  @Test
  public void getUserByIdTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      User userById = mapper.getUserById(2);
      System.out.println(userById);
    }
  }

二、INSERT，插入操作

加入插入方法

int insertUser(User user);

加入insert模块

<insert id="insertUser" parameterType="com.du.mybatis.pojo.User">
    insert into user(id, name, address)
    values (#{id}, #{name}, #{address});
</insert>

测试方法

  @Test
  public void insertUserTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      int res = mapper.insertUser(new User(10, "李白", "印度"));
      if (res > 0)
        System.out.println("插入成功");
      else
        System.out.println("插入失败");
      sqlSession.commit(); // 提交事务，必须！
    }
  }

涉及到修改数据库的操作，必须提交事务！！

三、UPDATE，修改操作

修改方法

int updateUser(User user);

加入update模块

<update id="updateUser" parameterType="com.du.mybatis.pojo.User">
    update user
    set name=#{name},
        address = #{address}
    where id = #{id};
</update>

测试代码

  @Test
  public void updateUserTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      int res = mapper.updateUser(new User(3, "杜甫", "西藏"));
      if (res > 0)
        System.out.println("更新成功");
      else
        System.out.println("更新失败");
      sqlSession.commit();
    }
  }

四、DELETE，删除操作

删除方法

int deleteUserByID(int id);

加入delete模块

<delete id="deleteUserByID" parameterType="int">
    delete
    from user
    where id = #{id};
</delete>

测试代码

  @Test
  public void deleteUserByIdTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      int res = mapper.deleteUserByID(2);
      if (res > 0)
        System.out.println("删除成功");
      else
        System.out.println("删除失败");
      sqlSession.commit();
    }
  }

五、多参数输入，通过`Map`实现

删除方法，输入参数为map

int deleteUserByNameAndAddress(Map<String, String> map);

加入delete模块

<delete id="deleteUserByNameAndAddress" parameterType="map">
    delete
    from user
    where name = #{name}
      and address = #{address};
</delete>

parameterType 为 map类型（小写表示，这是一个别名）
直接在#{}中取指就好
测试代码

  @Test
  public void deleteUserByNameAndAddressTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      Map<String, String> map = new HashMap<String, String>();
      map.put("name", "李白");
      map.put("address", "印度");
      int res = mapper.deleteUserByNameAndAddress(map);
      if (res > 0)
        System.out.println("删除成功");
      else
        System.out.println("删除失败");
      sqlSession.commit();
    }
  }

六、完整代码

public interface UserMapper {
  /**
   * 查询所有User
   *
   * @return
   */
  List<User> getUserList();

  /**
   * 通过ID查询User
   *
   * @return
   */
  User getUserById(Integer id);

  /**
   * 插入一个User
   *
   * @param user
   * @return 等于0 表示失败； >0 表示成功
   */
  int insertUser(User user);

  /**
   * 通过ID删除User
   *
   * @param id
   * @return
   */
  int deleteUserByID(int id);

  /**
   * 根据ID更新用户
   *
   * @param user
   * @return
   */
  int updateUser(User user);

  /**
   * 根据name和address删除元素
   * @param map
   * @return
   */
  int deleteUserByNameAndAddress(Map<String, String> map);
}

<?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">
<!--修改成对应的接口-->
<mapper namespace="com.du.mybatis.dao.UserMapper">
    <!--    id为接口中的方法名-->
    <!--  resultType 为查询的bean，记得是全路径！  -->
    <select id="getUserList" resultType="com.du.mybatis.pojo.User">
        select id, `name`, address
        from user;
    </select>
    <select id="getUserById" resultType="com.du.mybatis.pojo.User" parameterType="int">
        select id, `name`, address
        from user
        where id = #{id};
    </select>
    <insert id="insertUser" parameterType="com.du.mybatis.pojo.User">
        insert into user(id, name, address)
        values (#{id}, #{name}, #{address});
    </insert>
    <delete id="deleteUserByID" parameterType="int">
        delete
        from user
        where id = #{id};
    </delete>
    <update id="updateUser" parameterType="com.du.mybatis.pojo.User">
        update user
        set name=#{name},
            address = #{address}
        where id = #{id};
    </update>
    <delete id="deleteUserByNameAndAddress" parameterType="map">
        delete
        from user
        where name = #{name}
          and address = #{address};
    </delete>
</mapper>

public class UserMapperTest {
  @Test
  public void getUserListTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      List<User> userList = mapper.getUserList();
      for (User user : userList) {
        System.out.println(user);
      }
    }
  }

  @Test
  public void getUserByIdTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      User userById = mapper.getUserById(2);
      System.out.println(userById);
    }
  }

  @Test
  public void insertUserTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      int res = mapper.insertUser(new User(10, "李白", "印度"));
      if (res > 0)
        System.out.println("插入成功");
      else
        System.out.println("插入失败");
      sqlSession.commit(); // 提交事务，必须！
    }
  }

  @Test
  public void deleteUserByIdTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      int res = mapper.deleteUserByID(2);
      if (res > 0)
        System.out.println("删除成功");
      else
        System.out.println("删除失败");
      sqlSession.commit();
    }
  }

  @Test
  public void updateUserTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      int res = mapper.updateUser(new User(3, "杜甫", "西藏"));
      if (res > 0)
        System.out.println("更新成功");
      else
        System.out.println("更新失败");
      sqlSession.commit();
    }
  }

  @Test
  public void deleteUserByNameAndAddressTest() {
    try (SqlSession sqlSession = Utils.getSqlSession()) {
      UserMapper mapper = sqlSession.getMapper(UserMapper.class);
      Map<String, String> map = new HashMap<String, String>();
      map.put("name", "李白");
      map.put("address", "印度");
      int res = mapper.deleteUserByNameAndAddress(map);
      if (res > 0)
        System.out.println("删除成功");
      else
        System.out.println("删除失败");
      sqlSession.commit();
    }
  }
}

MyBatis之增删改查

一、SELECT，查操作

二、INSERT，插入操作

三、UPDATE，修改操作

四、DELETE，删除操作

五、多参数输入，通过Map实现

六、完整代码

五、多参数输入，通过`Map`实现