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三、MyBatisPlus条件构造器-Wrapper

2021-10-25 13:04:53 作者：互联网

文章目录

一、wapper介绍
二、AbstractWrapper

一、wapper介绍

在这里插入图片描述

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

@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 deleteTest(){
        //创建条件构造器对象
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        //以下条件构造器的方法入参中的 column 均表示数据库字段

        //ge、gt、le、lt、isNull、isNotNull
        /**
         * ge(greater than or equal):大于等于
         * gt(greater than)；大于
         * le(less than or equal):小于等于
         * lt(less than):小于
         */
        //条件为email为空，name不为空，age大于等于12小于等于22
        //    WHERE
        //        deleted=0
        //        AND name IS NOT NULL
        //        AND age >= 12
        //        AND age <= 22
        queryWrapper
                .isNull("email")
                .isNotNull("name")
                .ge("age",12)
                .le("age",22);

        int row = userMapper.delete(queryWrapper);
        System.out.println(row);
    }

Execute SQL：UPDATE user SET deleted=1 WHERE deleted=0 AND email IS NULL AND name IS NOT NULL AND age >= 12 AND age <= 22

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 selectOneTest(){
        //eq、ne即equal 、not equal
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        queryWrapper
                .eq("id",1);
        //selectOne正常返回一条记录，返回多条记录时会报错
        User user = userMapper.selectOne(queryWrapper);
        System.out.println(user);
    }

Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND id = 1

3、between、notBetween

包含大小边界

    @Test
    public void selectCountTest(){
        //between、notBetween
        //包含大小边界
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();
        queryWrapper
                .between("age",18,22);
        //    WHERE
        //        deleted=0
        //        AND age BETWEEN 18 AND 22
        List<User> users = userMapper.selectList(queryWrapper);
        users.forEach(System.out :: println);

    }

Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND age BETWEEN 18 AND 22

4、allEq

   @Test
    public void testSelectList(){
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        HashMap<String, Object> Map = new HashMap<>();
        //条件封装进Map
        Map.put("id",4);
        Map.put("name","Sandy");
        Map.put("age",21);
        //allEq:全匹配
        queryWrapper.allEq(Map);

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

Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND name = ‘Sandy’ AND id = 4 AND age = 21

5、like、notLike、likeLeft、likeRight

selectMaps返回Map集合列表

    @Test
    public void testSelectMaps(){
        //like、notLike、likeLeft、likeRight
        //selectMaps返回Map集合列表
        QueryWrapper<User> queryWrapper = new QueryWrapper<>();

        queryWrapper
                .notLike("name","e")    //LIKE '%e%'
                .likeRight("email","t");//LIKE 't%',同理likeLeft为LIKE '%t'
        //Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted FROM user WHERE deleted=0 AND name NOT LIKE '%e%' AND email LIKE 't%'
        List<Map<String, Object>> maps = userMapper.selectMaps(queryWrapper);
        maps.forEach(System.out ::println);
    }

Execute SQL：SELECT id,name,age,email,create_time,update_time,version,deleted 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
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()//不调用or则默认为使用 and 连
        .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 ?

标签：queryWrapper,MyBatisPlus,name,deleted,age,构造,Wrapper,id,user
来源： https://blog.csdn.net/m0_48481908/article/details/120949910