mybatisplus 条件构造器的使用

参考:  https://www.jianshu.com/p/ceb1df475021     文中的  三、mp的通用crud:

https://www.jianshu.com/p/c5537559ae3a

https://songzixian.com/mybatisplus/1354.html

实战:

delete_User

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    @Autowired
    TestServer testServer;
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@PostMapping("/aaa")
    public String delete_User3 (@RequestBody User user, HttpServletRequest HttpServletRequest) {
        testServer.aaa();
        testServer.bbb();
        return "完成更新操作";
    }

tbl_b2c_user

package com.dao.entity;


import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

@Data
@TableName(value = "tbl_b2c_user")//-------------------指定表名-------------这个不错
public class tbl_b2c_user {
    private int id;
    private String name;
}

tbl_b2c_userDao

package com.dao.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.dao.entity.tbl_b2c_user;

public interface tbl_b2c_userDao extends BaseMapper<tbl_b2c_user> {
}

TestServer

package com.server.Delete_user;

import com.baomidou.dynamic.datasource.annotation.DS;
import com.dao.entity.tbl_b2c_user;
import com.dao.mapper.tbl_b2c_userDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.ArrayList;
import java.util.List;

@DS("staging_B2c")
@Service
public class TestServer {
    //    测试使用构造器写sql
    @Autowired
    com.dao.mapper.tbl_b2c_userDao tbl_b2c_userDao;

//    更新操作
    public void aaa(){
    com.dao.entity.tbl_b2c_user tbl_b2c_user=new tbl_b2c_user();
    tbl_b2c_user.setId(2);
    tbl_b2c_user.setName("更新test测试2");
    tbl_b2c_userDao.updateById(tbl_b2c_user);//根据id进行更新，没有传值的属性就不会更新
}
    //in查询操作
    public void bbb(){
        List<Integer> idList = new ArrayList<>();
        idList.add(1);
        idList.add(2);
        idList.add(3);
        List<tbl_b2c_user> employees = tbl_b2c_userDao.selectBatchIds(idList);
        System.out.println(employees);
        employees.forEach(System.out::println);
    }

//模糊查询
public void ccc(){
    QueryWrapper<tbl_b2c_user> queryWrapper = new QueryWrapper<>();
    //模糊查询
    queryWrapper.like("name", "我是强爷");
    List<tbl_b2c_user> users = tbl_b2c_userDao.selectList(queryWrapper);

}

如果后面忘了mybatis操作数据库那么就按下面顺序看

mybatis 有xml 怎么用

https://www.cnblogs.com/kaibindirver/p/15025758.html

https://www.cnblogs.com/kaibindirver/p/15240918.html  

mybatis 注解使用

https://www.cnblogs.com/kaibindirver/p/15047034.html

mp多数据源使用

https://www.cnblogs.com/kaibindirver/p/15121436.html

记录一些常用的

线上项目，凡哥写的

可以用映射的方法 获取要比对的字段 如下面的 OrderEntity::getUserId  意思是 拿OrderEntity 里面的userId字段 

.eq(OrderEntity::getUserId, req.getUserId())