MyBatis Plus之wrapper用法

一、条件构造器关系

条件构造器关系介绍：

绿色框：抽象类 abstract
蓝色框：正常 class 类，可 new 对象
黄色箭头：父子类关系，箭头指向为父类

wrapper介绍：

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

二、项目实例

函数名	说明	举例
eq	等于 =	例：eq ( " name ", " 老叶 " ) —> name = ’ 老叶 ’
ne	不等于 <>	例：ne ( " name ", " 老叶 " ) —> name <> ’ 老叶 ’
gt	大于 >	例：gt ( " age ", 18 ) —> name > 18
ge	大于等于 >=	例：ge ( " age ", 18 ) —> name >= 18
lt	小于 <	例：lt ( " age ", 18 ) —> name < 18
le	小于等于 <=	例：le ( " age ", 18 ) —> name <= 18
between	Between 值1 and 值2	例：between ( " age ", 18, 30 ) —> age between 18 and 30
notBetween	NOT Between 值1 and 值2	例：notBetween ( " age ", 18, 30 ) —> age not between 18 and 30
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% ’
isNull	字段 IS NULL	例：isNull ( " name " ) —> name is null
isNotNull	字段 IS NOT NULL	例：isNotNull ( " name " ) —> name is not null
in	字段 IN (v0, v1, …)	例：in ( " age ", {1, 2, …} ) —> age in (1, 2, …)
notIn	字段 NOT IN (v0, v1, …)	例：notIn ( " age ", {1, 2, …} ) —> age not in (1, 2, …)
inSql	字段 IN ( sql语句 )	inSql ( " id ", " select id from table where id < 3 " ) —> id in ( select id from table where id < 3 )
notInSql	字段 NOT IN ( sql语句 )	notInSql ( " id ", " select id from table where id < 3 " ) —> id not in ( select id from table where id < 3 )
groupBy	分组：GROUP BY 字段, …	例：groupBy ( " id ", " name " ) —> group by id, name
orderBy	排序：ORDER BY 字段, …	例：orderBy ( " id ", " name " ) —> order by id ASC, name DESC
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
having	HAVING ( sql语句 )	例：having ( " sum ( age ) > { 0 } ", 11 ) —>having sum ( age ) > 11
or	拼接 OR	注意事项： 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) 例：eq ( " id ", 1 ).or ().eq ( " name ", " 老王 " ) —> id = 1 or name = ’ 老王 ’
and	嵌套 AND	例：and ( i -> i.eq ( " name ", " 李白 " ).ne ( " status ", " 活着 " ) ) —> and ( name = ’ 李白 ’ and status <> ’ 活着 ’ )
nested	正常嵌套，不带 AND 或者 OR	例：nested ( i -> i.eq ( " name ", " 李白 " ).ne ( " status ", " 活着 " ) ) —> ( name = ’ 李白 ’ and status <> ’ 活着 ’ )
apply	拼接 sql	注意事项： 该方法可用于数据库函数 动态入参的 params 对应前面 sqlHaving 内部的 { index } 部分，这样是不会有 sql 注入风险的，反之会有！ 例：apply ( " date_format ( dateColum, ’ %Y-%m-%d ’ ) = { 0 } ", " 2023-10-30 " ) —> date_format ( dateColumn, ’ %Y-%m-%d ’ ) = ’ 2023-10-30 ’
last	无视优化规则直接拼接到 sql 的最后	注意事项： 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 例：last ( " limit 1 " )
exists	拼接 EXISTS ( sql语句 )	例：exists ( " select id from table where age = 1 " ) —> exists ( select id from table where age = 1 )
notExists	拼接 NOT EXISTS ( sql语句 )	例：notExists ( " select id from table where age = 1 " ) —> not exists ( select id from table where age = 1 )

1、根据简单条件查询

    /**
     * 通过单个ID主键进行查询
     */
    @Test
    public void selectById() {
        User user = userMapper.selectById(1094592041087729666L);
        System.out.println(user);
    }
 
    /**
     * 通过多个ID主键查询
     */
    @Test
    public void selectByList() {
        List<Long> longs = Arrays.asList(1094592041087729666L, 1094590409767661570L);
        List<User> users = userMapper.selectBatchIds(longs);
        users.forEach(System.out::println);
    }
 
    /**
     * 通过Map参数进行查询
     */
    @Test
    public void selectByMap() {
        Map<String, Object> params = new HashMap<>();
        params.put("name", "郑梓妍");
        params.put("age", 18);
        List<User> users = userMapper.selectByMap(params);
        users.forEach(System.out::println);
    }

2、Wrapper 条件构造器

MyBatis Plus 还提供了 Wrapper 条件构造器，具体使用请看如下代码：

	/**
     * 名字包含雨
     * 且年龄小于40
     * 

     * WHERE name LIKE '%雨%' AND age < 40
     */
    @Test
    public void selectByWrapperOne() {
        QueryWrapper<User> wrapper = new QueryWrapper();
        wrapper.like("name", "雨").lt("age", 40);
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
 
    /**
     * 名字包含雨
     * 且年龄大于20小于40
     * 且邮箱不能为空
     * 

     * WHERE name LIKE '%雨%' AND age BETWEEN 20 AND 40 AND email IS NOT NULL
     */
    @Test
    public void selectByWrapperTwo() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.like("name", "雨").between("age", 20, 40).isNotNull("email");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
 
    /**
     * 名字为王姓
     * 或者年龄大于等于25
     * 按照年龄降序排序，年龄相同按照id升序排序
     * 

     * WHERE name LIKE '王%' OR age >= 25 ORDER BY age DESC , id ASC
     */
    @Test
    public void selectByWrapperThree() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.likeRight("name", "王").or()
                .ge("age", 25).orderByDesc("age").orderByAsc("id");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
 
    /**
     * 查询创建时间为2019年2月14
     * 且上级领导姓王
     * 

     * WHERE date_format(create_time,'%Y-%m-%d') = '2019-02-14' AND manager_id IN (select id from user where name like '王%')
     */
    @Test
    public void selectByWrapperFour() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.apply("date_format(create_time,'%Y-%m-%d') = {0}", "2019-02-14")
                .inSql("manager_id", "select id from user where name like '王%'");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
 
    /**
     * 查询王姓
     * 且年龄小于40或者邮箱不为空
     * 

     * WHERE name LIKE '王%' AND ( age < 40 OR email IS NOT NULL )
     */
    @Test
    public void selectByWrapperFive() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.likeRight("name", "王").and(qw -> qw.lt("age", 40).or().isNotNull("email"));
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
 
    /**
     * 查询王姓
     * 且年龄大于20 、年龄小于40、邮箱不能为空
     * 

     * WHERE name LIKE ? OR ( age BETWEEN ? AND ? AND email IS NOT NULL )
     */
    @Test
    public void selectByWrapperSix() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.likeRight("name", "王").or(
                qw -> qw.between("age", 20, 40).isNotNull("email")
        );
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
 
    /**
     * (年龄小于40或者邮箱不为空) 并且名字姓王
     * WHERE ( age < 40 OR email IS NOT NULL ) AND name LIKE '王%'
     */
    @Test
    public void selectByWrapperSeven() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.nested(qw -> qw.lt("age", 40).or().isNotNull("email"))
                .likeRight("name", "王");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
 
    /**
     * 查询年龄为30、31、32
     * WHERE age IN (?,?,?)
     */
    @Test
    public void selectByWrapperEight() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.in("age", Arrays.asList(30, 31, 32));
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }
 
    /**
     * 年龄为30、31、32
     * 查询一条数据
     * limit 1
     */
    @Test
    public void selectByWrapperNine() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.in("age", Arrays.asList(30, 31, 32)).last("limit 1");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
    }

三、具体使用操作

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);
}

	update user set deleted = 1 where deleted = 0 and name is null and age >= ? and email is not null

2、eq、ne

selectOne 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);
}

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 20 and 30

4、allEq

包含大小边界

@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 = 'Jack' and id = 2 and age = 20

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 '%e%' and email like 't%'

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

	inSql("age", "1,2,3") ---> age in (1,2,3)
	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

这里使用的是 UpdateWrapper 不调用 or 则默认为使用 and 连接

@Test
public void testUpdate() {
 
    //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 = 'Andy', age = 99, update_time = ? 
	where deleted = 0 and ((name like '%h%') or (age between 20 and 30))
	-- 名称包含’h‘，或名年龄在20到30岁之间

8、嵌套or、嵌套and

这里使用 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 = 'Andy', age = 99, update_time = ? 
	where deleted = 0 and name like '%h%' or (name = '%李白%' and age <> 20)
	-- 名称包含’h‘，或名称包含‘李白’且年龄不等于20岁

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 = '[email protected]'"); //可以有子查询
    int result = userMapper.update(user, userUpdateWrapper);
}

	update user set age = 99, update_time = ?, name = '老李头', email = '[email protected]' 
	where deleted = 0 and name like '%h%'

四、项目中的实际应用

实例1-- 包含 eq 相等的比较方法

实例2-- 包含 ge le 等比较方法；及分页查询

好事定律：每件事最后都会是好事，如果不是好事，说明还没到最后。