MyBatis的动态SQL！！！

一.if和where的使用。

1.首先在UserMapper接口中声明一个方法：

package com.by.mapper;

import com.by.pojo.User;

import java.util.List;

/**
 * 
Project: mybatis - UserMapper
 * 
Powered by scl On 2023-12-22 15:52:05
 * 
描述：

 *
 * @author 孙臣龙 [[email protected]]
 * @version 1.0
 * @since 17
 */
public interface UserMapper {
    /**
     * 动态SQL的练习 if/where
     * @return
     */
    List findAllById(User user);

}

2.在UserMapper.xml文件中实现这个接口：

    
    
        select * from user
        
            
                and id=#{id}
            
            
                and username=#{username}
            
            
                and sex=#{sex}
            
        
    

3.测试类：

/*
 * Copyright (c) 2020, 2023,  All rights reserved.
 *
 */
package com.by;

import com.by.mapper.AccountMapper;
import com.by.mapper.RoleMapper;
import com.by.mapper.UserMapper;
import com.by.pojo.Account;
import com.by.pojo.Role;
import com.by.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;


/**
 * 
Project: mybatis - MyBatisTest
 * 
Powered by scl On 2023-12-18 11:44:53
 * 
描述：

 *
 * @author 孙臣龙 [[email protected]]
 * @version 1.0
 * @since 17
 */
public class MyBatisTestRole {

    private InputStream inputStream;
    private SqlSession sqlSession;

    @Before
    public void init() throws IOException {
        // 加载配置文件
        String resource = "mybatis-config.xml";
        inputStream = Resources.getResourceAsStream(resource);

        // 创建sqlSessionFActory
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 获得数据的绘画实例
        sqlSession = sessionFactory.openSession();
    }



    /**
     * 动态SQL if/where
     *
     * @throws IOException
     */
    @Test
    public void findUserById() {
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setUsername("李星云");
        user.setSex("男");
        user.setId(42);
        List userList = userMapper.findAllById(user);
        for (User user1 : userList) {
            System.out.println(user1);
        }
    }
   
    @After
    public void close() throws IOException {
        inputStream.close();
        sqlSession.close();
    }

}

4.结果展示：

二. set的使用

1.首先在UserMapper接口中声明一个方法：

package com.by.mapper;

import com.by.pojo.User;

import java.util.List;

/**
 * 
Project: mybatis - UserMapper
 * 
Powered by scl On 2023-12-22 15:52:05
 * 
描述：

 *
 * @author 孙臣龙 [[email protected]]
 * @version 1.0
 * @since 17
 */
public interface UserMapper {

    /**
     * 动态SQL的练习  set
     */
    void updateUser(User user);

   
}

2.在UserMapper.xml文件中实现这个方法：

   
    
    
        update user
        
            
                username=#{username},
            
            
                sex=#{sex},
            
        
        where id=#{id}
    

3.实现类：

/*
 * Copyright (c) 2020, 2023,  All rights reserved.
 *
 */
package com.by;

import com.by.mapper.AccountMapper;
import com.by.mapper.RoleMapper;
import com.by.mapper.UserMapper;
import com.by.pojo.Account;
import com.by.pojo.Role;
import com.by.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;


/**
 * 
Project: mybatis - MyBatisTest
 * 
Powered by scl On 2023-12-18 11:44:53
 * 
描述：

 *
 * @author 孙臣龙 [[email protected]]
 * @version 1.0
 * @since 17
 */
public class MyBatisTestRole {

    private InputStream inputStream;
    private SqlSession sqlSession;

    @Before
    public void init() throws IOException {
        // 加载配置文件
        String resource = "mybatis-config.xml";
        inputStream = Resources.getResourceAsStream(resource);

        // 创建sqlSessionFActory
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 获得数据的绘画实例
        sqlSession = sessionFactory.openSession();
    }

    /**
     * 动态SQL set
     *
     * @throws IOException
     */
    @Test
    public void updateUser() {
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setUsername("侯卿");
        user.setSex("男");
        user.setId(42);
        userMapper.updateUser(user);
    }
  

    @After
    public void close() throws IOException {
        inputStream.close();
        sqlSession.close();
    }

}

4.结果展示：

三.trim的使用

1.首先在User Mapper接口中声明方法：

package com.by.mapper;

import com.by.pojo.User;

import java.util.List;

/**
 * 
Project: mybatis - UserMapper
 * 
Powered by scl On 2023-12-22 15:52:05
 * 
描述：

 *
 * @author 孙臣龙 [[email protected]]
 * @version 1.0
 * @since 17
 */
public interface UserMapper {

    /**
     * 动态SQL练习 trim
     */
    void insertUser(User user);
}

2.在UserMapper.xml文件中实现这个方法：、

    
    
        insert into user
        
            
                username,
            
            
                sex,
            
            
                address,
            
            
                birthday,
            
        
        
            
                #{username},
            
            
                #{sex},
            
            
               #{address},
            
            
                #{birthday},
            
        
    

3.实现类：

/*
 * Copyright (c) 2020, 2023,  All rights reserved.
 *
 */
package com.by;

import com.by.mapper.AccountMapper;
import com.by.mapper.RoleMapper;
import com.by.mapper.UserMapper;
import com.by.pojo.Account;
import com.by.pojo.Role;
import com.by.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;


/**
 * 
Project: mybatis - MyBatisTest
 * 
Powered by scl On 2023-12-18 11:44:53
 * 
描述：

 *
 * @author 孙臣龙 [[email protected]]
 * @version 1.0
 * @since 17
 */
public class MyBatisTestRole {

    private InputStream inputStream;
    private SqlSession sqlSession;

    @Before
    public void init() throws IOException {
        // 加载配置文件
        String resource = "mybatis-config.xml";
        inputStream = Resources.getResourceAsStream(resource);

        // 创建sqlSessionFActory
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        // 获得数据的绘画实例
        sqlSession = sessionFactory.openSession();
    }

    /**
     * 动态SQL trim
     *
     * @throws IOException
     */
    @Test
    public void insertUser() {
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setUsername("侯卿");
        user.setSex("男");
        userMapper.insertUser(user);
    }




    @After
    public void close() throws IOException {
        inputStream.close();
        sqlSession.close();
    }

}

4.结果展示：

四.foreach的使用

1.UserMapper接口中定义方法：

    /**
     * 动态SQL练习 foreach
     */
    void deleteUserByIds(@Param("arrIds") Integer[] arrIds);

2.UserMapper.xml文件中实现方法：

 
    
        delete from user where id in
        
            #{id}
        
    

3.测试类：

/**
     * 动态SQL foreach
     *
     * @throws IOException
     */
    @Test
    public void deleteUserByIds() {
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        //List list=new ArrayList<>();
        //list.add(41);
        //list.add(42);
        //list.add(43);
        Integer[] integers = new Integer[]{41,42,43};
        userMapper.deleteUserByIds(integers);
    }