2、CRUD

1、namespace

namespace中的包名要和接口的包名一致！

2、select

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

3、insert

4、update

5、Delete

【示例】测试CRUD

（1）编写接口；

package com.baidou.dao;

import com.baidou.pojo.User;

import java.util.List;

public interface UserMapper {

    /**
     * 获取全部的用户
     */
    List<User> getUserList();

    /**
     * 通过ID获取用户
     * @param id
     * @return
     */
    List<User> getUserById(int id);

    /**
     * 添加用户
     * @param user
     * @return
     */
    int addUser(User user);

    /**
     * 修改用户信息
     * @param user
     * @return
     */
    int updateUser(User user);

    /**
     * 删除用户
     * @param id
     * @return
     */
    int deleteUser(int id);

}

（2）编写对应mapper的sql；

<?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:绑定一个对应的Dao/Mapper接口 -->
<mapper namespace="com.baidou.dao.UserMapper">
    <!-- select查询语句，id:绑定对应方法名，resultType:返回值类型 -->
    <select id="getUserList" resultType="com.baidou.pojo.User">
        select  * from mybatis.user ;
    </select>

    <select id="getUserById" resultType="com.baidou.pojo.User" parameterType="int">
        select * from mybatis.user where id = #{id} ;
    </select>

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

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

    <delete id="deleteUser" parameterType="int">
        delete from mybatis.user where id =#{id} ;
    </delete>
</mapper>

（3）测试

package com.baidou.dao;

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

import java.util.List;

public class UserDaoTest {

    @Test
    public void test() {
        // 获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 方式一:getmapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();


        // 方式二:
        // List<User> userList = sqlSession.selectList("com.baidou.dao.UserDao.getUserList");

        for (User user : userList) {
            System.out.println(user);
        }

        //关闭SqlSession
        sqlSession.close();
    }

    @Test
    public void getUserById() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> user = mapper.getUserById(1);
        System.out.println(user);
        // 关闭SqlSession
        sqlSession.close();
    }

    @Test
    public void addUser() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        System.out.println(mapper.addUser(new User("风清扬", "fenqingyang")) > 0 ? "添加成功" : "添加失败");
        // 增删改需要提交事务
        sqlSession.commit();
        // 关闭SqlSession
        sqlSession.close();
    }

    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        System.out.println(mapper.updateUser(new User(3, "王富贵", "wangfugui")) > 0 ? "修改成功" : "修改失败");
        // 提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void deleteUser() {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        System.out.println(mapper.deleteUser(3) > 0 ? "删除成功" : "删除失败");
        // 提交事务
        sqlSession.commit();
        // 关闭SqlSession
        sqlSession.close();
    }
}

注意：增删改需要提交事务！！！