[JPA] Spring Boot JPA Query Creation

JPA Query Creation

JPA를 이용해서 코딩할 경우, interface에서 적절히 메서드 이름을 지정하는 것 만으로 query method를 만들 수 있다.

예시는 다음과 같다.

// Question Entity

import lombok.Getter;
import lombok.Setter;

import javax.persistence.*;
import java.time.LocalDateTime;
import java.util.List;

@Getter @Setter
@Entity
public class Question {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(length = 200)
    private String subject;

    @Column(columnDefinition = "TEXT")
    private String content;

    private LocalDateTime createDate;

    @OneToMany(mappedBy = "question", cascade = CascadeType.REMOVE)
    private List<Answer> answerList;

}

 

 

// JPA Repository Interface

import org.springframework.data.jpa.repository.JpaRepository;

public interface QuestionRepository extends JpaRepository<Question, Integer> {
    Question findBySubject(String subject);
    Question findBySubjectAndContent(String subject, String content);
}

이 때, findBySubject와 findBySubjectAndContent는 구현하지 않았는데도 잘 동작한다.

어떻게 이러한 것이 가능한 것일까?

JPA Query Creation

JPA는 내부적으로 method의 이름을 분석해서 그에 적절한 query를 만들어낸다.

Spring Data 공식 문서에 따르면, method에서 인식되는 keyword는 다음과 같다.

KeywordSampleJPQL snippet

Distinct	findDistinctByLastnameAndFirstname	select distinct …​ where x.lastname = ?1 and x.firstname = ?2
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, Null	findByAge(Is)Null	… 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.firstname) = UPPER(?1)

https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa.query-methods.query-creation

Spring Data JPA - Reference Documentation

내부 동작원리

method 이름을 가지고 query를 생성하는 내부 동작원리는 다음을 보면 알 수 있다.

기본적으로 method 이름을 정규식으로 분석함으로써 동작하는 것이다.

public class PartTree implements Streamable<OrPart> {

	/*
	 * We look for a pattern of: keyword followed by
	 *
	 *  an upper-case letter that has a lower-case variant \p{Lu}
	 * OR
	 *  any other letter NOT in the BASIC_LATIN Uni-code Block \\P{InBASIC_LATIN} (like Chinese, Korean, Japanese, etc.).
	 *
	 * @see <a href="https://www.regular-expressions.info/unicode.html">https://www.regular-expressions.info/unicode.html</a>
	 * @see <a href="https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html#ubc">Pattern</a>
	 */
	private static final String KEYWORD_TEMPLATE = "(%s)(?=(\\p{Lu}|\\P{InBASIC_LATIN}))";
	private static final String QUERY_PATTERN = "find|read|get|query|search|stream";
	private static final String COUNT_PATTERN = "count";
	private static final String EXISTS_PATTERN = "exists";
	private static final String DELETE_PATTERN = "delete|remove";
	private static final Pattern PREFIX_TEMPLATE = Pattern.compile( //
			"^(" + QUERY_PATTERN + "|" + COUNT_PATTERN + "|" + EXISTS_PATTERN + "|" + DELETE_PATTERN + ")((\\p{Lu}.*?))??By");

https://github.com/spring-projects/spring-data-commons/blob/main/src/main/java/org/springframework/data/repository/query/parser/PartTree.java

GitHub - spring-projects/spring-data-commons: Spring Data Commons. Interfaces and code shared between the various datastore spec