一、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 ：看名称也明白就是能用于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); }
UPDATE user SET age=?, update_time=?, name=?, email = ‘123@qq.com’ WHERE deleted=0 AND name LIKE ?
