Mybatis——增删改查

• • CRUD(增删改查)
  • • 1.namespace 命名空间
    • 2.select
    • 3.insert
    • 4.update
    • 5.delete
    • 注意：增删改需要提交事务
    • 万能Map
    • 模糊查询

只需改动UserMapper.java UserMapper.xml UserDao.test

namespace中的包名要和Dao / mapper 接口的包一致。

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

//根据id查询用户
User getUserById(int sid);

2.编写对应的mapper中的sql语句

    select * from mybatis.user where sid=#{id}

 
3.测试
 
    @Test
    public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        //获取Mapper --> 拿到对象 --> 直接调方法
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User user = mapper.getUserById(1);
        System.out.println(user);

        sqlSession.close();
    }
 
 
3.insert 

    insert into mybatis.user(sid, sname, pwd) values (#{sid},#{sname},#{pwd})

 
//增删改需要提交事务
@Test//增加
public void addUser(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();

    //获取Mapper --> 拿到对象 --> 直接调方法
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    mapper.addUser(new User(4,"slugger","654321"));

    //提交事物
    sqlSession.commit();

    sqlSession.close();
}
 
 
4.update 

    update mybatis.user set sname = #{sname},pwd = #{pwd} where sid = #{sid};

 
@Test//修改
public void updateUser(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();

    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    mapper.updateUser(new User(2,"MaxPark","123123"));

    sqlSession.commit();
    sqlSession.close();
}
 
 
5.delete 

    delete from mybatis.user where sid = #{sid};

 
@Test//删除
public void deleteUser(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    mapper.deleteUser(3);
    sqlSession.commit();

    sqlSession.close();
}
 
注意：增删改需要提交事务 
resource用路径/
namespace用 .
 
 
 
万能Map 
若我们实体类，或数据库中的表，字段或者参数过多，我们应该考虑使用Map
 
int addUser2(Map map);
 
    
        insert into mybatis.user(sid, sname, pwd) values (#{userid},#{userName},#{password})
    
 
    @Test
    public void addUser2(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        Map map = new HashMap();
        map.put("userid",3);
        map.put("userName","afei");
        map.put("password","111111");

        mapper.addUser2(map);
        sqlSession.commit();
        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,例：【parameterType=“int”】可以省略不写
多个参数用Map,或者注解
 
 
模糊查询 
Java代码执行的时候，传递通配符% %
 
List userList = mapper.getUserLike("s");
 
在sql拼接中使用通配符
 

    select * from mybatis.user where sname like "%"#{value}"%"

//模糊查询
List getUserLike(String value);

    select * from mybatis.user where sname like "%"#{value}"%"

//模糊查询
@Test
public void getUserLike(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);

    List userList = mapper.getUserLike("s");
    for (User user : userList) {
        System.out.println(user);
    }
    sqlSession.close();
}

查询结果

User{sid=1, sname='feliks', pwd='123456'}
User{sid=4, sname='slugger', pwd='654321'}
User{sid=5, sname='spiderman', pwd='222222'}