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

@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); } 

();
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 ?