Add, delete, modify, check

Advanced

CRUD

1.namespace

The package name in the namespace must be the same as the registration of the mapper interface

2.select

• Select, query

• id: the name of the namespace method

• resultType: The return value of the SQL statement execution

• parmeterType: parameter type

1. Write an interface

public  interface UserMapper {   
  // Query all users 
   List <User> getUserList ();  
   // Query a user according to ID    
 User getUserById ( int id); 
    // insert a user   
 int addUser (User user); 
   // Modify user   
 int upsateUser (User user);  
  // Delete a user   
  int deleteUser ( int id);}

2. Write the corresponding SQL statement in the mapper

<mapper namespace="com.kuang.dao.UserMapper">  
  <!--select 查询语句-->  
  <select id="getUserList" resultType="com.kuang.pojo.User">     
   select * from mybatis.user;   
 </select>  
    <select id="getUserById" parameterType="int" resultType="com.kuang.pojo.User">    
  select * FROM mybatis.user where id=#{id}/*#id是可变的参数*/ 
   </select>     

3. Test

public class UserDaoTest {
    @Test/*查看所有*/ 
   public void test() { 
       SqlSession sqlSession = MybatisUtils.getSqlSession(); 
       UserMapper userDao = sqlSession.getMapper(UserMapper.class);       
  List<User> userList = userDao.getUserList();       
           for (User user : userList) {           
        System.out.println(user);       
 }       
 sqlSession.close();    
}   
  @Test/*查看指定的*/
public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();/*获取执行SQL的对象*/
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);/*获取UserMaper的对象*/
        User userById = mapper.getUserById(1);    
               System.out.println(userById);    
    sqlSession.close();  
  } 
  @Test  
  public void addUser(){ 
       SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class); 
       inthaha = mapper.addUser ( new User (4, "haha", "d" )); 
      if (haha! = 0 ) { 
         System.out.println ( "Successfully changed" + haha ​​+ "个 点" );    
   } 
       sqlSession .commit (); / * Addition, deletion and modification need to submit transactions * / 
       sqlSession.close ();    
 }    
 @Test / * Modify a content * / 
    public  void upsateUser () { 
        SqlSession sqlSession = MybatisUtils.getSqlSession (); 
       UserMapper mapper = sqlSession. getMapper (UserMapper. class );
         int i = mapper.upsateUser ( new User(4, "狗蛋", "123456"));
        sqlSession.commit();        sqlSession.close();  
  }   
 @Test  
    public void deletdUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int i = mapper.deleteUser(4);       
    if (i>0){ 
          System.out.println("成功删除id为"+i+"的用户"); 
              }        
        sqlSession.commit();
        sqlSession.close();    }

3.insert

 <!- The attributes in the object can be directly removed- > < insert id = "addUser" parameterType = "com.kuang.pojo.User" >     insert into mybatis.user (id, name, pwd) value (# {id }, # {name}, # {pwd}) </ insert >  

4.update

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

5.delete

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

important point:

Add, delete, modify, commit transactions

If you read wrong, read from back to front