上篇文章介绍了 “使用jpa的 Repository 自定义声明式查询方法” （declare query method）
使用jpa的 Repository 自定义声明式查询方法
凡是继承了Repository的或继承其子接口的，都可以使用自定义的声明式查询方法，如下示例：
public interface PersonQueryRepo extends Repository {
// declare query method
// 声明式查询方法
// 1. count 计数
long countByName(String name);
// 2. get/find/stream/query/read 查询
Person readFirstByAge(int age);
// 3. delete/remove 删除
int deleteById(long id);
}
声明式查询方法可以分3大类：
1 计数类 ：以count开头，返回数值类型
2 查询类：以get/find/stream/query/read开头，返回Person类或其集合
3 删除类： 以delete/remove开始，返回int类型
在以上方法之后还有可以加入下面的关键词：
jpa声明式查询方法名称关键词
其中声明式查询方法的方法名称支持的关键字 如下：
| Keyword | Sample | JPQL snippet |
|---|---|---|
And | findByLastnameAndFirstname | … where x.lastname = ?1 and x.firstname = ?2 |
Or | findByLastnameOrFirstname | … where x.lastname = ?1 or x.firstname = ?2 |
Is,Equals | findByFirstname,findByFirstnameIs,findByFirstnameEquals | … where x.firstname = ?1 |
Between | findByStartDateBetween | … where x.startDate between ?1 and ?2 |
LessThan | findByAgeLessThan | … where x.age < ?1 |
LessThanEqual | findByAgeLessThanEqual | … where x.age <= ?1 |
GreaterThan | findByAgeGreaterThan | … where x.age > ?1 |
GreaterThanEqual | findByAgeGreaterThanEqual | … where x.age >= ?1 |
After | findByStartDateAfter | … where x.startDate > ?1 |
Before | findByStartDateBefore | … where x.startDate < ?1 |
IsNull | findByAgeIsNull | … where x.age is null |
IsNotNull,NotNull | findByAge(Is)NotNull | … where x.age not null |
Like | findByFirstnameLike | … where x.firstname like ?1 |
NotLike | findByFirstnameNotLike | … where x.firstname not like ?1 |
StartingWith | findByFirstnameStartingWith | … where x.firstname like ?1 (parameter bound with appended %) |
EndingWith | findByFirstnameEndingWith | … where x.firstname like ?1 (parameter bound with prepended %) |
Containing | findByFirstnameContaining | … where x.firstname like ?1 (parameter bound wrapped in %) |
OrderBy | findByAgeOrderByLastnameDesc | … where x.age = ?1 order by x.lastname desc |
Not | findByLastnameNot | … where x.lastname <> ?1 |
In | findByAgeIn(Collection<Age> ages) | … where x.age in ?1 |
NotIn | findByAgeNotIn(Collection<Age> ages) | … where x.age not in ?1 |
True | findByActiveTrue() | … where x.active = true |
False | findByActiveFalse() | … where x.active = false |
IgnoreCase | findByFirstnameIgnoreCase | … where UPPER(x.firstame) = UPPER(?1) |
因此，jpa中使用以上三类操作，加上上表中的关键词作为约束条件，就可以极限大部分的查询和日常操作。
此外，对于jpa中更新的update操作，推荐使用@Query注解，详见http://jvm123.com/2019/09/springboot-jpa.html 。