[MyBatisPlus]条件构造器wapper

Posted 2022-03-16 唐火

wapper简介

QueryWrapper

组装查询条件

查询用户名包含a，年龄在20到30之间，邮箱信息不为null的用户信息

package com.xxxx.mybatisplus;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.xxxx.mybatisplus.mapper.UserMapper;
import com.xxxx.mybatisplus.pojo.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
public class MyBatisPlusWrapperTest 

    @Autowired
    private UserMapper userMapper;

    @Test
    public void test01()
    
        // 查询用户名包含a，年龄在20到30之间，邮箱信息不为null的用户信息
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.like("user_name","a")
                .between("age",20,30)
                .isNotNull("email");
        List<User> list = userMapper.selectList(queryWrapper);
        list.forEach(System.out::println);

    

组装排序条件

查询用户信息，按照年龄的降序排序，若年龄相同，则按照id升序排序

    @Test
    public void test02()
    
        // 查询用户信息，按照年龄的降序排序，若年龄相同，则按照id升序排序
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByDesc("age")
                .orderByAsc("uid");
        List<User> list = userMapper.selectList(queryWrapper);
        list.forEach(System.out::println);
    

组装删除条件

删除邮箱地址为null的用户信息

 @Test
    public void test03()
    
        // 删除邮箱地址为null的用户信息
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.isNull("email");
        int result = userMapper.delete(queryWrapper);
        System.out.println("result = "+result);
    

使用QueryWrapper实现修改功能

将(年龄大于20并且用户名中包含有a) 或邮箱为null的用户信息修改

 @Test
    public void test04()
    
        // 将(年龄大于20并且用户名中包含有a) 或邮箱为null的用户信息修改
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.gt("age",20)
                .like("user_name","a")
                .or()
                .isNull("email");
        User user  = new User();
        user.setName("小明");
        user.setEmail("[e-mail]");
        int result = userMapper.update(user, queryWrapper);
        System.out.println("result = "+result);

    

条件的优先级

将用户名中包含有a并且(年龄大于20或邮箱为null)的用户信息修改

@Test
    public void test05()
    
        // 优先级不同，我们实现2
        // 1.将(年龄大于20并且用户名中包含有a)或邮箱为null的用户信息修改
        // 2.将用户名中包含有a并且(年龄大于20或邮箱为null)的用户信息修改


        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.like("user_name","a")
                // lambda表达式中的条件优先执行
               .and(i -> i.gt("age",20).or().isNull("email"));

        User user = new User();
        user.setName("小红");
        user.setEmail("[e-mail]");
        int result = userMapper.update(user, queryWrapper);
        System.out.println("result = "+result);

    

组装select字句

查询用户的用户名，年龄，邮箱信息

 @Test
    public void test06()
    
        // 查询用户的用户名，年龄，邮箱信息
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.select("user_name","age","email");

        List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);
        maps.forEach(System.out::println);
    

组装子查询

查询id小于等于100的用户信息

 @Test
    public void test07()
    
        // 查询id小于等于100的用户信息
        // SELECT uid AS id,user_name AS name,age,email,is_deleted FROM user WHERE is_deleted=0 AND (uid IN (select uid from user where uid <= 100))
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.inSql("uid","select uid from user where uid <= 100");
        List<User> list = userMapper.selectList(queryWrapper);
        list.forEach(System.out::println);
    

UpdateWrapper

UpdateWrapper实现修改功能

将用户名中含有a并且(年龄大于20或邮箱为null)的用户信息修改

@Test
    public void test08()
    
        // 将用户名中含有a并且(年龄大于20或邮箱为null)的用户信息修改
        UpdateWrapper<User> updateWrapper = new UpdateWrapper<>();
        updateWrapper.like("user_name","a")
                .and(i -> i.gt("age",20).or().isNull("email"));

        updateWrapper.set("user_name","小黑").set("email","[e-mail]");
        int result = userMapper.update(null, updateWrapper);
        System.out.println("result = "+result);

    

模拟开发中组件条件的情况

 @Test
    public void test09()
    
        String username = "";
        Integer ageBegin = 20;
        Integer ageEnd = 30;

        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        // isNotBlank 判断某个字符串是否不为空字符串,不为null,不为空白符
        if (StringUtils.isNotBlank(username))
        
            queryWrapper.like("username",username);
        

        if (ageBegin != null)
        
            queryWrapper.ge("age",ageBegin);
        

        if (ageEnd != null)
        
            queryWrapper.le("age",ageEnd);

        
        List<User> list = userMapper.selectList(queryWrapper);
        list.forEach(System.out::println);
    

但是上面的方法比较麻烦，所以我们用下面这种方法！

使用condition组装条件

 @Test
    public void test10()
    
        String username = "a";
        Integer ageBegin = null;
        Integer ageEnd = 30;
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.like(StringUtils.isNotBlank(username),"user_name",username)
                .ge(ageBegin!=null,"age",ageBegin)
                .le(ageEnd != null,"age",ageEnd);

        List<User> list = userMapper.selectList(queryWrapper);
        list.forEach(System.out::println);
    

LambdaQueryWrapper

• 防止我们写字段名的时候写错

 @Test
    public void test11()
    
        String username = "a";
        Integer ageBegin = null;
        Integer ageEnd = 30;
        LambdaQueryWrapper<User> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.like(StringUtils.isNotBlank(username),User::getName,username)
                .ge(ageBegin != null,User::getAge,ageBegin)
                .le(ageEnd != null,User::getAge,ageEnd);
        List<User> list = userMapper.selectList(queryWrapper);
        list.forEach(System.out::println);

    

LambdaUpdateWrapper

@Test
    public void test12()
    
        // 将用户名中含有a并且(年龄大于20或邮箱为null)的用户信息修改
        LambdaUpdateWrapper<User> updateWrapper = new LambdaUpdateWrapper<>();
        updateWrapper.like(User::getName,"a")
                .and(i -> i.gt(User::getAge,20).or().isNull(User::getEmail));

        updateWrapper.set(User::getName,"小黑").set(User::getEmail,"[e-mail]");
        int result = userMapper.update(null, updateWrapper);
        System.out.println("result = "+result);