CRUD

CRUD

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: 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

   User getUserById(int id);//根据ID查询用户
   

2. 编写对应mapper中的sql语句

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

3. 测试

   @Test
   public void getUserById(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
       User user = mapper.getUserById(2);
       System.out.println(user);
       sqlSession.close();
   }
   

3.insert

int addUser(User user);//插入一个用户

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

3. @Test
   public void addUser(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
       int res = mapper.addUser(new User(4, "李四", "123456"));
       sqlSession.commit();//提交事务
       sqlSession.close();
   }
   

4.update

int updateUser(User user);//修改用户

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

@Test
public void updateUser(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    int res = mapper.updateUser(new User(4,"李大四","1234"));
    sqlSession.commit();//提交事务
    sqlSession.close();
}

5.delete

int deleteUser(int id);//删除一个用户

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

@Test
public void deleteUser(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    int res = mapper.deleteUser(4);
    sqlSession.commit();//提交事务
    sqlSession.close();
}

6.模糊查询

1. List<User> getUserLike(String value);//模糊查询
   

2. <select id="getUserLike" resultType="cn.pinked.pojo.User">
       select * from mybatis.user where name like #{value}
   </select>
   

3. @Test
   public void getUserLike(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
       List<User> userList = mapper.getUserLike("%张%");
       for (User user : userList) {
           System.out.println(user);
       }
       sqlSession.close();
   }
   

7.map的使用

如果在实体类中,或数据库中的表,字段或者参数过多,可以使用map传递数据

1. int addUser2(Map<String, Object> map);//使用map
   

2. <insert id="addUser2" parameterType="map">
       insert into mybatis.user(id, name, pwd) values(#{userid},#{username},#{password});
   </insert>
   

3. @Test
   public void addUser2(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
       HashMap<String, Object> map = new HashMap<String, Object>();
       map.put("userid",4);
       map.put("username","李四");
       map.put("password","123456");
       int res = mapper.addUser2(map);
       sqlSession.commit();//提交事务
       sqlSession.close();
   }
   

​

map传递参数,直接在sql中取出key即可 ---------------------- parameterType="map"

对象传递参数,直接在sql中取出对象的属性即可-------------parameterType="Object"

只有一个基本类型参数的情况下,可以直接在sql中取到

多个参数用map或者注解