MyBatis-Plus之Wrapper条件构造器

Love The Way You Lie 2022-10-31 15:59 339阅读 0赞

# Wrapper条件构造器 #

### 文章目录 ###

*  Wrapper条件构造器
 *   *  一、wapper介绍
     *  二、AbstractWrapper
     *   *  1、ge(>=)、gt(>)、le、lt、isNull、isNotNull
         *  2、eq、ne
         *  3、between、notBetween
         *  4、allEq
         *  5、like、notLike、likeLeft、likeRight
         *  6、in、notIn、inSql、notinSql、exists、notExists
         *  7、or、and
         *  8、嵌套or、嵌套and
         *  9、orderBy、orderByDesc、orderByAsc
         *  10、last
         *  11、指定要查询的列
         *  12、set、setSql

## 一、wapper介绍 ##

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Wrapper ： 条件构造抽象类，最顶端父类
        AbstractWrapper ： 用于查询条件封装，生成 sql 的 where 条件
            QueryWrapper ： Entity 对象封装操作类，不是用lambda语法
            UpdateWrapper ： Update 条件封装，用于Entity对象更新操作
        AbstractLambdaWrapper ： Lambda 语法使用 Wrapper统一处理解析 lambda 获取 column。
            LambdaQueryWrapper ：看名称也能明白就是用于Lambda语法使用的查询Wrapper
            LambdaUpdateWrapper ： Lambda 更新封装Wrapper

**注入UserMapper组件**

@RunWith(SpringRunner.class)
    @SpringBootTest
    public class QueryWrapperTests { 
        
        @Autowired
        private UserMapper userMapper;
    }

## 二、AbstractWrapper ##

注意：以下条件构造器的方法入参中的 column 均表示数据库字段

### 1、ge(>=)、gt(>)、le、lt、isNull、isNotNull ###

@Test
    public void testDelete() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper
            .isNull("name")
            .ge("age", 12)
            .isNotNull("email");
        int result = userMapper.delete(queryWrapper);
        System.out.println("delete return count = " + result);
    }

SQL：UPDATE user SET deleted=1 WHERE deleted=0 AND name IS NULL AND age >= ? AND email IS NOT NULL

### 2、eq、ne ###

注意：seletOne返回的是一条实体记录，当出现多条时会报错

@Test
    public void testSelectOne() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.eq("name", "Tom");
        User user = userMapper.selectOne(queryWrapper);
        System.out.println(user);
    }

SELECT id,name,age,email,create\_time,update\_time,deleted,version FROM user WHERE deleted=0 AND name = ?

### 3、between、notBetween ###

包含大小边界

@Test
    public void testSelectCount() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.between("age", 20, 30);
        Integer count = userMapper.selectCount(queryWrapper);
        System.out.println(count);
    }

SELECT COUNT(1) FROM user WHERE deleted=0 AND age BETWEEN ? AND ?

### 4、allEq ###

@Test
    public void testSelectList() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        Map<String, Object> map = new HashMap<>();
        map.put("id", 2);
        map.put("name", "Jack");
        map.put("age", 20);
        queryWrapper.allEq(map);
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }

SELECT id,name,age,email,create\_time,update\_time,deleted,version  
FROM user WHERE deleted=0 AND name = ? AND id = ? AND age = ?

### 5、like、notLike、likeLeft、likeRight ###

selectMaps返回Map集合列表

@Test
    public void testSelectMaps() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper
            .notLike("name", "e")
            .likeRight("email", "t");
        List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);//返回值是Map列表
        maps.forEach(System.out::println);
    }

SELECT id,name,age,email,create\_time,update\_time,deleted,version  
FROM user WHERE deleted=0 AND name NOT LIKE ? AND email LIKE ?

### 6、in、notIn、inSql、notinSql、exists、notExists ###

in、notIn：  
 notIn(“age”,\{1,2,3\})—>age not in (1,2,3)  
 notIn(“age”, 1, 2, 3)—>age not in (1,2,3)

inSql、notinSql：可以实现子查询  
 例: inSql(“age”, “1,2,3,4,5,6”)—>age in (1,2,3,4,5,6)  
 例: inSql(“id”, “select id from table where id < 3”)—>id in (select id from table where id < 3)

@Test
    public void testSelectObjs() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        //queryWrapper.in("id", 1, 2, 3);
        queryWrapper.inSql("id", "select id from user where id < 3");
        List<Object> objects = userMapper.selectObjs(queryWrapper);//返回值是Object列表
        objects.forEach(System.out::println);
    }

SELECT id,name,age,email,create\_time,update\_time,deleted,version  
FROM user WHERE deleted=0 AND id IN (select id from user where id < 3)

### 7、or、and ###

注意：这里使用的是 UpdateWrapper  
不调用or则默认为使用 and 连

@Test
    public void testUpdate1() { 
        //修改值
        User user = new User();
        user.setAge(99);
        user.setName("Andy");
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper
            .like("name", "h")
            .or()
            .between("age", 20, 30);
        int result = userMapper.update(user, userUpdateWrapper);
        System.out.println(result);
    }

UPDATE user SET name=?, age=?, update\_time=? WHERE deleted=0 AND name LIKE ? OR age BETWEEN ? AND ?

### 8、嵌套or、嵌套and ###

这里使用了lambda表达式，or中的表达式最后翻译成sql时会被加上圆括号

@Test
    public void testUpdate2() { 
        //修改值
        User user = new User();
        user.setAge(99);
        user.setName("Andy");
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper
            .like("name", "h")
            .or(i -> i.eq("name", "李白").ne("age", 20));
        int result = userMapper.update(user, userUpdateWrapper);
        System.out.println(result);
    }

UPDATE user SET name=?, age=?, update\_time=?  
WHERE deleted=0 AND name LIKE ?  
OR ( name = ? AND age <> ? )

### 9、orderBy、orderByDesc、orderByAsc ###

@Test
    public void testSelectListOrderBy() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByDesc("id");
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }

SELECT id,name,age,email,create\_time,update\_time,deleted,version  
FROM user WHERE deleted=0 ORDER BY id DESC

### 10、last ###

直接拼接到 sql 的最后  
注意：只能调用一次,多次调用以最后一次为准 有sql注入的风险,请谨慎使用

@Test
    public void testSelectListLast() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.last("limit 1");
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }

SELECT id,name,age,email,create\_time,update\_time,deleted,version  
FROM user WHERE deleted=0 limit 1

### 11、指定要查询的列 ###

@Test
    public void testSelectListColumn() { 
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper.select("id", "name", "age");
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out::println);
    }

SELECT id,name,age FROM user WHERE deleted=0

### 12、set、setSql ###

最终的sql会合并 user.setAge()，以及 userUpdateWrapper.set() 和 setSql() 中 的字段

@Test
    public void testUpdateSet() { 
        //修改值
        User user = new User();
        user.setAge(99);
        //修改条件
        UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
        userUpdateWrapper
            .like("name", "h")
            .set("name", "老李头")//除了可以查询还可以使用set设置修改的字段
            .setSql(" email = '123@qq.com'");//可以有子查询
        int result = userMapper.update(user, userUpdateWrapper);
    }

UPDATE user SET age=?, update\_time=?, name=?, email = ‘123@qq.com’ WHERE deleted=0 AND name LIKE ?

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