====== Description ======

====== User Guide ======

===== Query Method =====
JPA 모듈은 문자열로 쿼리를 정의하거나 메서드에서 파생되어진 쿼리를 사용하는 방법을 지원한다.
==== 쿼리생성 ====
스트링으로 쿼리를 정의하는 예시 :
<code java>
public interface UserRepository extends Repository<User, Long> {
List<User> findByEmailAddressAndLastname(String emailAddress, String lastname);
</code>
JPA표준 API는 위의 스트링으로 정의된 쿼리를 다음 쿼리로 변경한다.
<code java>
select u from User u where u.emailAddress = ?1 and u.lastname = ?2
</code>
==== 지원하는 메서드 명 ====
^  Keyword  ^  Sample  ^ JPQL snippet ^
| ''And''  | findByLastnameAndFirstname  |… where x.lastname = ?1 and x.firstname = ?2  |
| ''Or''  | findByLastnameOrFirstname  |… where x.lastname = ?1 or x.firstname = ?2  |
| ''Between''  | findByStartDateBetween  |… where x.startDate between 1? and ?2  |
| ''LessThan''  | findByAgeLessThan  |… where x.age < ?1  |
| ''GreaterThan''  | findByAgeGreaterThan  |… 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> age)  |… where x.age not in ?1  |
| ''True''  | findByActiveTrue()  |… where x.active = true  |
| ''False''  | findByActiveFalse()  |… where x.active = false  |

===== Using @Query =====
Using named queries to declare queries for entities is a valid approach and works fine for a small number of queries. As the queries themselves are tied to the Java method that executes them you actually can bind them directly using the Spring Data JPA @Query annotation rather than annotating them to the domain class. This will free the domain class from persistence specific information and co-locate the query to the repository interface.

쿼리메서드에 정의된 쿼리들은 xml에 선언된 @NamedQuery나 named queries보다 우선하여 처리됩니다.

@Query를 이용한 쿼리 선언 예제 :

<code java>
public interface UserRepository extends JpaRepository<User, Long> {
  @Query("select u from User u where u.emailAddress = ?1")
  User findByEmailAddress(String emailAddress);
}
</code>

==== 파라미터를 활용한 @Query ====
By default Spring Data JPA will use position based parameter binding as described in all the samples above. This makes query methods a little error prone to refactoring regarding the parameter position. To solve this issue you can use @Param annotation to give a method parameter a concrete name and bind the name in the query:
기본적으로 스프링 데이터 JPA는 위의 모든 샘플에 설명 된대로 파라미터가 바인딩 된 바인딩 위치 기반 매개 변수를 사용합니다.
파라미터를 이용한 쿼리 선언 예제 :

<code java>
public interface UserRepository extends JpaRepository<User, Long> {

  @Query("select u from User u where u.firstname = :firstname or u.lastname = :lastname")
  User findByLastnameOrFirstname(@Param("lastname") String lastname,
                                 @Param("firstname") String firstname);
}
</code>



====== References ======

http://static.springsource.org/spring-data/data-jpa/docs/current/reference/html/jpa.repositories.html