namespace

namespace中的包名要和Dao/mapper接口的包名一致

crud

选择,查询语句

• id:对应namespace中的方法名;
• resultType:Sql语句执行的返回值
• parameterType:参数类型

编写接口

package com.qin.dao;

import com.qin.pojo.User;

import java.util.List;

public interface UserMapper {
    //查询全部用户
    List<User> getUserList();
    //根据id查询用户
    User getUserById(int id);
    //插入一个用户
    int addUser(User user);
    //更新一个用户
    int updateUser(User user);
    //删除一个用户
    int deleteUserByid(int id);
}

编写对应的mapper中的sql语句

<?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">
<!--类似继承UserDao接口-->
<mapper namespace="com.qin.dao.UserMapper">
<!--    实现UserDao里面的方法-->
    <select id="getUserList" resultType="com.qin.pojo.User">
    select * from mybatis.user;
   </select>
<!--    对象中的属性可以直接拿到-->
    <select id="getUserById" parameterType="int" resultType="com.qin.pojo.User">
        select * from `user` where id=#{id}
    </select>
    <insert id="addUser" parameterType="com.qin.pojo.User">
        insert into `user` values (#{id},#{name},#{pwd})
    </insert>
    <update id="updateUser" parameterType="com.qin.pojo.User">
        update `user` set `name` = #{name} , pwd = #{pwd} where id = #{id}
    </update>

    <delete id="deleteUserByid" parameterType="int">
        delete from `user` where id=#{id}
    </delete>
</mapper>

测试

package com.qin.dao;

import com.qin.pojo.User;
import com.qin.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {
    @Test
    public void getUser(){
        //使用工具类获得SqlSesison
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = userMapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }
    @Test
    public void testGetUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //使用SqlSeeion对象的getMapper方法 得到一个UserMapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //使用得到的UserMapper对象 调用里面的方法
        User user = mapper.getUserById(1);
        System.out.println(user);

        sqlSession.close();
    }
    //增删改需要提交事务
    @Test
    public void testAddUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //使用SqlSeeion对象的getMapper方法 得到一个UserMapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //使用得到的UserMapper对象 调用里面的方法
        int row = mapper.addUser(new User(4,"灰太狼","123456"));
        System.out.println(row);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //使用SqlSeeion对象的getMapper方法 得到一个UserMapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //使用得到的UserMapper对象 调用里面的方法
        int row = mapper.updateUser(new User(4,"红太狼","123456"));
        System.out.println(row);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //使用SqlSeeion对象的getMapper方法 得到一个UserMapper对象
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //使用得到的UserMapper对象 调用里面的方法
        int row = mapper.deleteUserByid(4);
        System.out.println(row);
        sqlSession.commit();
        sqlSession.close();
    }
}

Map

使用map传递参数

编写接口

//使用map传递参数
//插入一个用户
int addUser2(Map map);

配置接口

<insert id="addUser2" parameterType="Map">
    <!-- 传递的参数名是map中的键 -->
    insert into `user` values (#{id},#{name},#{pwd})
</insert>

测试

@Test
public void addUser2(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    //使用SqlSeeion对象的getMapper方法 得到一个UserMapper对象
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    //使用得到的UserMapper对象 调用里面的方法
    Map<String,Object> map = new HashMap<>();
    map.put("table","`user`");
    map.put("id","4");
    map.put("name","孙悟空");
    map.put("pwd","666666");
    int row = mapper.addUser2(map);
    System.out.println(row);
    sqlSession.commit();
    sqlSession.close();
}

模糊查询

编写接口

//模糊查询
List<User> getUserList2(String name);

配置接口

使用通配符

<select id="getUserList2" resultType="com.qin.pojo.User">
    select * from `user` where `name` like "%"#{name}"%"
</select>

测试

@Test
public void getUser2(){
    //使用工具类获得SqlSesison
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    List<User> userList = userMapper.getUserList2("孙");
    for (User user : userList) {
        System.out.println(user);
    }
    sqlSession.close();
}