mybatis-plus教程-mybatis-plus条件构造器

今天药忘吃喽~ 2023-06-13 08:54 82阅读 0赞

## 条件构造器 ##

在MP中，Wrapper接口的实现类关系如下：  
![在这里插入图片描述][format_png]

可以看到，AbstractWrapper和AbstractChainWrapper是重点实现，接下来我们重点学习AbstractWrapper以及其子类。

说明:

QueryWrapper(LambdaQueryWrapper) 和 UpdateWrapper(LambdaUpdateWrapper) 的父类

用于生成 sql 的 where 条件, entity 属性也用于生成 sql 的 where 条件

注意: entity 生成的 where 条件与 使用各个 api 生成的 where 条件没有任何关联行为

官网文档地址：https://mybatis.plus/guide/wrapper.html

### allEq ###

#### 说明 ####

allEq(Map<R, V> params)
    allEq(Map<R, V> params, boolean null2IsNull)
    allEq(boolean condition, Map<R, V> params, boolean null2IsNull)

*  全部eq(或个别isNull)

个别参数说明:

params : key为数据库字段名,value为字段值

null2IsNull : 为true则在map的value为null时调用 isNull 方法,为false时则忽略value为null的

*  例1: allEq(\{id:1,name:“老王”,age:null\})—>id = 1 and name = ‘老王’ and age is null
 *  例2: allEq(\{id:1,name:“老王”,age:null\}, false)—>id = 1 and name = ‘老王’
    
    allEq(BiPredicate<R, V> filter, Map<R, V> params)  
    allEq(BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull)  
    allEq(boolean condition, BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull)

个别参数说明:

filter : 过滤函数,是否允许字段传入比对条件中

params 与 null2IsNull : 同上

*  例1: allEq((k,v) -> k.indexOf(“a”) > 0, \{id:1,name:“老王”,age:null\})—>name = ‘老王’ and age is null
 *  例2: allEq((k,v) -> k.indexOf(“a”) > 0, \{id:1,name:“老王”,age:null\}, false)—>name = ‘老王’

#### 测试用例 ####

package com.pbteach.mp;
    
    import com.pbteach.mp.mapper.UserMapper;
    import com.pbteach.mp.pojo.User;
    import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.test.context.junit4.SpringRunner;
    
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class UserMapperTest {
    
        @Autowired
        private UserMapper userMapper;
    
        @Test
        public void testWrapper() {
            QueryWrapper<User> wrapper = new QueryWrapper<>();
    
            //设置条件
            Map<String,Object> params = new HashMap<>();
            params.put("name", "曹操");
            params.put("age", "20");
            params.put("password", null);
    
    //        wrapper.allEq(params);//SELECT * FROM tb_user WHERE password IS NULL AND name = ? AND age = ?
    //        wrapper.allEq(params,false); //SELECT * FROM tb_user WHERE name = ? AND age = ?
    
    //        wrapper.allEq((k, v) -> (k.equals("name") || k.equals("age")) ,params);//SELECT * FROM tb_user WHERE name = ? AND age = ?
    
            List<User> users = this.userMapper.selectList(wrapper);
            for (User user : users) {
                System.out.println(user);
            }
    
        }
    
    }

### 基本比较操作 ###

*  eq
    
     *  等于 =
 *  ne
    
     *  不等于 <>
 *  gt
    
     *  大于 >
 *  ge
    
     *  大于等于 >=
 *  lt
    
     *  小于 <
 *  le
    
     *  小于等于 <=
 *  between
    
     *  BETWEEN 值1 AND 值2
 *  notBetween
    
     *  NOT BETWEEN 值1 AND 值2
 *  in
    
     *  字段 IN (value.get(0), value.get(1), …)
 *  notIn
    
     *  字段 NOT IN (v0, v1, …)

测试用例：

package com.pbteach.mp;
    
    import com.pbteach.mp.mapper.UserMapper;
    import com.pbteach.mp.pojo.User;
    import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.test.context.junit4.SpringRunner;
    
    import java.util.List;
    
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class UserMapperTest {
    
        @Autowired
        private UserMapper userMapper;
    
        @Test
        public void testEq() {
            QueryWrapper<User> wrapper = new QueryWrapper<>();
    
            //SELECT id,user_name,password,name,age,email FROM tb_user WHERE password = ? AND age >= ? AND name IN (?,?,?)
            wrapper.eq("password", "123456")
                   .ge("age", 20)
                   .in("name", "李四", "王五", "赵六");
    
            List<User> users = this.userMapper.selectList(wrapper);
            for (User user : users) {
                System.out.println(user);
            }
    
        }
    
    }

### 模糊查询 ###

*  like
    
     *  LIKE ‘%值%’
     *  例: like(“name”, “王”)—>name like ‘%王%’
 *  notLike
    
     *  NOT LIKE ‘%值%’
     *  例: notLike(“name”, “王”)—>name not like ‘%王%’
 *  likeLeft
    
     *  LIKE ‘%值’
     *  例: likeLeft(“name”, “王”)—>name like ‘%王’
 *  likeRight
    
     *  LIKE ‘值%’
     *  例: likeRight(“name”, “王”)—>name like ‘王%’

测试用例：

package com.pbteach.mp;
    
    import com.pbteach.mp.mapper.UserMapper;
    import com.pbteach.mp.pojo.User;
    import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.test.context.junit4.SpringRunner;
    
    import java.util.List;
    
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class UserMapperTest {
    
        @Autowired
        private UserMapper userMapper;
    
        @Test
        public void testWrapper() {
            QueryWrapper<User> wrapper = new QueryWrapper<>();
    
            //SELECT id,user_name,password,name,age,email FROM tb_user WHERE name LIKE ?
            //Parameters: %曹%(String)
            wrapper.like("name", "曹");
    
            List<User> users = this.userMapper.selectList(wrapper);
            for (User user : users) {
                System.out.println(user);
            }
    
        }
    
    }

### 排序 ###

*  orderBy
    
     *  排序：ORDER BY 字段, …
     *  例: orderBy(true, true, “id”, “name”)—>order by id ASC,name ASC
 *  orderByAsc
    
     *  排序：ORDER BY 字段, … ASC
     *  例: orderByAsc(“id”, “name”)—>order by id ASC,name ASC
 *  orderByDesc
    
     *  排序：ORDER BY 字段, … DESC
     *  例: orderByDesc(“id”, “name”)—>order by id DESC,name DESC

测试用例：

### 逻辑查询 ###

*  or
    
     *  拼接 OR
     *  主动调用or表示紧接着下一个方法不是用and连接!(不调用or则默认为使用and连接)
 *  and
    
     *  AND 嵌套
     *  例: and(i -> i.eq(“name”, “李白”).ne(“status”, “活着”))—>and (name = ‘李白’ and status <> ‘活着’)

测试用例：

package com.pbteach.mp;
    
    import com.pbteach.mp.mapper.UserMapper;
    import com.pbteach.mp.pojo.User;
    import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.test.context.junit4.SpringRunner;
    
    import java.util.List;
    
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class UserMapperTest {
    
        @Autowired
        private UserMapper userMapper;
    
        @Test
        public void testWrapper() {
            QueryWrapper<User> wrapper = new QueryWrapper<>();
    
            //SELECT id,user_name,password,name,age,email FROM tb_user WHERE name = ? OR age = ?
            wrapper.eq("name","李四").or().eq("age", 24);
    
            List<User> users = this.userMapper.selectList(wrapper);
            for (User user : users) {
                System.out.println(user);
            }
    
        }
    
    }

### select ###

在MP查询中，默认查询所有的字段，如果有需要也可以通过select方法进行指定字段。

package com.pbteach.mp;
    
    import com.pbteach.mp.mapper.UserMapper;
    import com.pbteach.mp.pojo.User;
    import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.test.context.junit4.SpringRunner;
    
    import java.util.List;
    
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class UserMapperTest {
    
        @Autowired
        private UserMapper userMapper;
    
        @Test
        public void testWrapper() {
            QueryWrapper<User> wrapper = new QueryWrapper<>();
    
            //SELECT id,name,age FROM tb_user WHERE name = ? OR age = ?
            wrapper.eq("name", "李四")
                    .or()
                    .eq("age", 24)
                    .select("id", "name", "age");
    
            List<User> users = this.userMapper.selectList(wrapper);
            for (User user : users) {
                System.out.println(user);
            }
    
        }
    
    }

[format_png]: https://imgconvert.csdnimg.cn/aHR0cDovL3d3dy5wYnRlYWNoLmNvbS9wb3N0L2phdmFfZGlzdHJpYnV0L215YmF0aXMtcGx1cy0wMS8xNTU2NDUxMzAyMDE1LnBuZw?x-oss-process=image/format,png