MyBatis（二）

3、CURD（增删改查）

1. namespace

namespace中的包名要和Dao/Mapper接口的包名一致

2. select

选择，查询语句；

• 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；

  1. 编写接口

     public interface UserMapper {
         //查询所有用户
         public List<User> getUserList();
         //插入用户
         public void addUser(User user);
     }

  2. 编写对应的mapper中的sql语句

     <insert id="addUser" parameterType="com.kuang.pojo.User">
         insert into user (id,name,password) values (#{id}, #{name}, #{password})
     </insert>

  3. 测试

     @Test
     public void test2() {
         SqlSession sqlSession = MybatisUtils.getSqlSession();
         UserMapper mapper = sqlSession.getMapper(UserMapper.class);
         User user  = new User(3,"黑子","666");
         mapper.addUser(user);
         //增删改一定要提交事务
         sqlSession.commit();
     ​
         //关闭sqlSession
         sqlSession.close();
     }

     注意：增删改查一定要提交事务：

     sqlSession.commit();

3. Insert

4. update

5. Delete

示例代码(依次)

package com.alice.dao;
import com.alice.pojo.User;
import java.util.List;
public interface UserMapper {
    List<User> getUserList();
    User getUserById(String id);
    int addUser(User user);
    int updateUser(User user);
    int deleteUser(String id);
    List<User> getUserListByLike(String name);
}
​

<?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="com.alice.dao.UserMapper">
    <select id="getUserList" resultType="User">
        select * from `mybatis-alice-01`.user;
    </select>
    <select id="getUserListByLike" resultType="User">
        select * from `mybatis-alice-01`.user where name like "%"#{name}"%";
    </select>
    <select id="getUserById" resultType="User" parameterType="String">
        select * from `mybatis-alice-01`.user where id = #{id};
    </select>
    <insert id="addUser" parameterType="User">
        insert into `mybatis-alice-01`.user (id ,name ,pad ) values (#{id},#{name },#{pad });
    </insert>
    <update id="updateUser" parameterType="User">
        update `mybatis-alice-01`.user
        set name = #{name } ,pad=#{pad }
        where id= #{id};
    </update>
    <delete id="deleteUser" parameterType="String">
        delete from `mybatis-alice-01`.user where id=#{id};
    </delete>
</mapper>

package com.alice.dao;
import com.alice.pojo.User;
import com.alice.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
​
import java.util.List;
​
public class UserDaoTest {
    @Test
    public void test(){
        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 getUserById(){
        SqlSession sqlSession=MyBatisUtils.getSqlSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        User user=userMapper.getUserById("1234567");
        System.out.println(user);
        sqlSession.close();
    }
    @Test
    public void addUser(){
        SqlSession sqlSession=MyBatisUtils.getSqlSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        userMapper.addUser(new User("123456789","9","123456"));
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteANUpdate(){
        SqlSession sqlSession=MyBatisUtils.getSqlSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        userMapper.updateUser(new User("1234567","ali","123456"));
        userMapper.deleteUser("123456789");
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void selectLike(){
        SqlSession sqlSession=MyBatisUtils.getSqlSession();
        UserMapper userMapper=sqlSession.getMapper(UserMapper.class);
        List<User>userList=userMapper.getUserListByLike("%a%");
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }
}
​