3.增删改查的实现（1）

3.1
只需要更改接口，配置文件和测试类，工具类和实体类不用再变。

写接口---在UserMapper中

写sql语句---UserMapper.xml中

写测试类---UserDaoTest中

namespace中的包名要和接口中的包名一致

注意事项

增删改要提交事务 sqlSession.commit();

标签不要匹配错

核心配置文件必须严格正确

3.2
xml中的语句：

id:对应namespace中的方法名

resultType：SQL语句的返回值

parameterType:要传的参数的类型

 

编写接口

    //查询所有用户
    List<User> getUserList();
    //根据id查询用户
    User getUserById(int id);
    //插入用户
    int addUser(User user);
    //修改用户
    int updateUser(User user);
    //删除用户
    int deleteUser(int id);
编写配置文件（写SQL语句）

<mapper namespace="com.mu.dao.UserMapper">
    <select id="getUserList" resultType="com.mu.pojo.User">
        select * from user
    </select>
​
    <select id="getUserById" resultType="com.mu.pojo.User" parameterType="int">
        select * from user where id = #{id}
    </select>
​
    <insert id="addUser" parameterType="com.mu.pojo.User">
        insert into mybatis.user(id,name,pwd) values(#{id},#{name},#{pwd});
    </insert>
​
    <update id="updateUser" parameterType="com.mu.pojo.User">
         update mybatis.user set name=#{name},pwd=#{pwd} where id=#{id};
    </update>
​
    <delete id="deleteUser" parameterType="int">
        delete from user where id = #{id};
    </delete>
</mapper>
编写类

package com.mu.dao;
import com.mu.pojo.User;
import com.mu.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
​
import java.util.List;
​
public class UserDaoTest {
    @Test
    public void test(){
        //第一步：获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //方式一：getMapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
​
        for (User user : userList) {
            System.out.println(user);
        }
        sqlSession.close();//关闭
    }
    @Test
    public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
​
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.getUserById(1);
​
        System.out.println(user);
        sqlSession.close();
    }
@Test
    public void addUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.addUser (new User(4,"aaa","aaa"));
        sqlSession.commit();
        sqlSession.close();
    }
@Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.updateUser(new User(4,"bbb","bbb"));
        sqlSession.commit();
        sqlSession.close();
    }
​
    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int res = mapper.deleteUser(4);
        sqlSession.commit();
        sqlSession.close();
    }
}