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mybatis-plus中wrapper的用法实例详解

2022-02-22 16:04:33 作者：乞力马扎罗の黎明

本文给大家介绍了mybatis-plus中wrapper的用法,包括条件构造器关系、项目实例及具体使用操作，本文通过实例代码给大家介绍的非常详细，需要的朋友可以参考下

用到了wrapper，整理资料记录一下，以备后续复习。

一、条件构造器关系介绍

条件构造器关系介绍：

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

wapper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

1、根据主键或者简单的查询条件进行查询

 /**
     * 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
    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
    public void selectByMap() {
        Map<String, Object> params = new HashMap<>();
        params.put("name", "张雨琪");
        List<User> users = userMapper.selectByMap(params);

2、MyBatis-Plus还提供了Wrapper条件构造器，具体使用看如下代码：

/**
     * 名字包含雨并且年龄小于40
     * <p>
     * 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
     * 年龄大于20小于40
     * 邮箱不能为空
     * WHERE name LIKE '%雨%' AND age BETWEEN 20 AND 40 AND email IS NOT NULL
    public void selectByWrapperTwo() {
        QueryWrapper<User> wrapper = Wrappers.query();
        wrapper.like("name", "雨").between("age", 20, 40).isNotNull("email");
     * 名字为王性
     * 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
    public void selectByWrapperThree() {
        wrapper.likeRight("name", "王").or()
                .ge("age", 25).orderByDesc("age").orderByAsc("id");
     * 查询创建时间为2019年2月14
     * 并且上级领导姓王
     * WHERE date_format(create_time,'%Y-%m-%d') = '2019-02-14' AND manager_id IN (select id from user where name like '王%')
    public void selectByWrapperFour() {
        wrapper.apply("date_format(create_time,'%Y-%m-%d') = {0}", "2019-02-14")
                .inSql("manager_id", "select id from user where name like '王%'");
     * 查询王姓
     * 并且年龄小于40或者邮箱不为空
     * WHERE name LIKE '王%' AND ( age < 40 OR email IS NOT NULL )
    public void selectByWrapperFive() {
        wrapper.likeRight("name", "王").and(qw -> qw.lt("age", 40).or().isNotNull("email"));
     * 并且年龄大于20 、年龄小于40、邮箱不能为空
     * WHERE name LIKE ? OR ( age BETWEEN ? AND ? AND email IS NOT NULL )
    public void selectByWrapperSix() {
        wrapper.likeRight("name", "王").or(
                qw -> qw.between("age", 20, 40).isNotNull("email")
        );
     * (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%'
    public void selectByWrapperSeven() {
        wrapper.nested(qw -> qw.lt("age", 40).or().isNotNull("email"))
                .likeRight("name", "王");
     * 查询年龄为30、31、32
     * WHERE age IN (?,?,?)
    public void selectByWrapperEight() {
        wrapper.in("age", Arrays.asList(30, 31, 32));
     * 查询一条数据
     * limit 1
    public void selectByWrapperNine() {
        wrapper.in("age", Arrays.asList(30, 31, 32)).last("limit 1");

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);
}

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);
}

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);9
    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)

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 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);
}

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 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 ( name = ? AND age <> ? )

9、orderBy、orderByDesc、orderByAsc

@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);
}

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 ?

参考文档

1、https://blog.csdn.net/m0_37034294/article/details/82917234

2、https://blog.csdn.net/kepengs/article/details/112345870

3、https://blog.csdn.net/weixin_39615889/article/details/107086931

4、https://blog.csdn.net/weixin_38111957/article/details/91447509

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