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Kotlin UInt 타입은 JPA와 쓸 수 있을까?

배경

Java에서는 unsigned 자료형은 지원하지 않는다. (사실 JVM 스펙 상에서도 unsigned는 char를 제외하고는 지원되지 않는다.) 반면, Kotlin 에서는 UInt 타입을 지원한다. Kotlin에서는 어떻게 UInt 타입을 지원하냐면, Int 타입을 래핑한 클래스로 제공한다.

그렇다면, JPA는 Kotlin UInt 타입을 지원해줄까? UInt 와는 어떻게 동작할까? (UInt 만이 아닌 다른 unsigned 모두)

가설

  1. UInt 타입은 unsigned 자료형과 원활하게 동작할 것이다.
  2. UInt 타입은 결국 Int 타입을 wrapping 한 것으로 잘 동작하지 않을 것이다.
  3. UInt 타입은 signed int 타입과 함께 사용해 unsigned value 를 다룰 수 있을 것이다.

목표

제일 최고의 상황은 JPA 가 unsigned 자료형을 잘 지원해서 코틀린에서 JPA 를 쓸 때, 매핑문제를 해소해주는 것이다.

사용 기술

  • Kotlin 1.6.21
  • Spring Boot 2.6.7
  • Spring Web MVC
  • Spring Data JPA
  • Gradle 7.4.1

개발 환경

  • Mac OS Monterey 12.3.1
  • IntelliJ IDEA 2021.3.3
  • Amazon Corretto JDK 11.1
  • Docker Desktop 4.6.1
    • MySql 5.7

검증

1. UInt 타입은 unsigned 자료형과 원활하게 동작할 것이다.

거짓. JPA는 UInt타입을 지원하지 않는다.

'Basic' attribute type should not be 'UInt' 
 Inspection info: Reports property type mismatch for JPA attributes.

2. UInt 에 대한 Converter 를 만들면 원활하게 동작할 것이다.(UintTest 참조)

일단 Spring이 UInt 타입에 대한 Convert 를 지원하지 않아 Long 타입으로 받은 후 변환을 거쳤다.

POST http://localhost:8080/uint?mau=2147483648

발생한 로그 및 예외 로그

2022-04-24 00:48:41.917 DEBUG 66735 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : POST "/uint?mau=2147483648", parameters={masked}
2022-04-24 00:48:41.923 DEBUG 66735 --- [nio-8080-exec-1] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to dev.idion.kotlinuint.uint.UintTestController#create(Long)
2022-04-24 00:48:41.993  INFO 66735 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티 값: 2147483648
2022-04-24 00:48:41.993  INFO 66735 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장될 값: -2147483648
2022-04-24 00:48:41.993  INFO 66735 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장된 값: -2147483648
2022-04-24 00:48:41.993  INFO 66735 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티로 반환될 값: 2147483648
2022-04-24 00:48:41.999 DEBUG 66735 --- [nio-8080-exec-1] org.hibernate.SQL                        : 
    insert 
    into
        uint_test
        (mau) 
    values
        (?)
2022-04-24 00:48:42.013  INFO 66735 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티 값: 2147483648
2022-04-24 00:48:42.013  INFO 66735 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장될 값: -2147483648
2022-04-24 00:48:42.028  WARN 66735 --- [nio-8080-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 1264, SQLState: 22001
2022-04-24 00:48:42.028 ERROR 66735 --- [nio-8080-exec-1] o.h.engine.jdbc.spi.SqlExceptionHelper   : Data truncation: Out of range value for column 'mau' at row 1
2022-04-24 00:48:42.047 DEBUG 66735 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Failed to complete request: org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; nested exception is org.hibernate.exception.DataException: could not execute statement
2022-04-24 00:48:42.057 ERROR 66735 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; nested exception is org.hibernate.exception.DataException: could not execute statement] with root cause

com.mysql.cj.jdbc.exceptions.MysqlDataTruncation: Data truncation: Out of range value for column 'mau' at row 1

값 자체가 음수가 되어 DB와 타입 불일치로 실패하는 모습을 볼 수 있다.

컨버터 구현을 바꿔볼까?

바뀐 컨버터 구현

@Converter
class UIntConverter : AttributeConverter<UInt?, Long?> {

    private val logger: Logger = LoggerFactory.getLogger(UIntConverter::class.java)

    override fun convertToDatabaseColumn(attribute: UInt?): Long? {
        logger.info("엔티티 값: {}", attribute)
        logger.info("DB에 저장될 값: {}", attribute?.toLong())
        return attribute?.toLong()
    }

    override fun convertToEntityAttribute(dbData: Long?): UInt? {
        logger.info("DB에 저장된 값: {}", dbData)
        logger.info("엔티티로 반환될 값: {}", dbData?.toUInt())
        return dbData?.toUInt()
    }
}

발생한 로그 (valiate 여서 발생한다.)

2022-04-24 00:57:41.614 ERROR 66961 --- [  restartedMain] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.tool.schema.spi.SchemaManagementException: Schema-validation: wrong column type encountered in column [mau] in table [uint_test]; found [int (Types#INTEGER)], but expecting [bigint (Types#BIGINT)]

반환타입은 Long 이어서 bigint 를 기대하는데, unsigned int 는 int 로 판단한다.

application.propeties 에 수정을 가하자

...
spring.jpa.hibernate.ddl-auto=none
...

놀랍게도 동작한다.

2022-04-24 01:00:31.947 DEBUG 67036 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : POST "/uint?mau=2147483648", parameters={masked}
2022-04-24 01:00:31.952 DEBUG 67036 --- [nio-8080-exec-1] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to dev.idion.kotlinuint.uint.UintTestController#create(Long)
2022-04-24 01:00:32.023  INFO 67036 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티 값: 2147483648
2022-04-24 01:00:32.024  INFO 67036 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장될 값: 2147483648
2022-04-24 01:00:32.024  INFO 67036 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장된 값: 2147483648
2022-04-24 01:00:32.024  INFO 67036 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티로 반환될 값: 2147483648
2022-04-24 01:00:32.029 DEBUG 67036 --- [nio-8080-exec-1] org.hibernate.SQL                        : 
    insert 
    into
        uint_test
        (mau) 
    values
        (?)
2022-04-24 01:00:32.045  INFO 67036 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티 값: 2147483648
2022-04-24 01:00:32.045  INFO 67036 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장될 값: 2147483648
2022-04-24 01:00:32.085 DEBUG 67036 --- [nio-8080-exec-1] m.m.a.RequestResponseBodyMethodProcessor : Using 'application/json', given [*/*] and supported [application/json, application/*+json, application/json, application/*+json]
2022-04-24 01:00:32.086 DEBUG 67036 --- [nio-8080-exec-1] m.m.a.RequestResponseBodyMethodProcessor : Nothing to write: null body
2022-04-24 01:00:32.087 DEBUG 67036 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed 200 OK

조회가 안된다.. 원인은 컴파일된 클래스에 no args constructor가 없어서다. (Spring 은 잘 되는데... 버근가??)

2022-04-24 01:19:13.194 DEBUG 67723 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : GET "/uint", parameters={}
2022-04-24 01:19:13.202 DEBUG 67723 --- [nio-8080-exec-1] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to dev.idion.kotlinuint.uint.UintTestController#all()
2022-04-24 01:19:13.409 DEBUG 67723 --- [nio-8080-exec-1] org.hibernate.SQL                        : 
    select
        uinttest0_.id as id1_0_,
        uinttest0_.mau as mau2_0_ 
    from
        uint_test uinttest0_
2022-04-24 01:19:13.472 DEBUG 67723 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Failed to complete request: org.springframework.orm.jpa.JpaSystemException: No default constructor for entity:  : dev.idion.kotlinuint.uint.UintTest; nested exception is org.hibernate.InstantiationException: No default constructor for entity:  : dev.idion.kotlinuint.uint.UintTest
2022-04-24 01:19:13.477 ERROR 67723 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.orm.jpa.JpaSystemException: No default constructor for entity:  : dev.idion.kotlinuint.uint.UintTest; nested exception is org.hibernate.InstantiationException: No default constructor for entity:  : dev.idion.kotlinuint.uint.UintTest] with root cause

org.hibernate.InstantiationException: No default constructor for entity:  : dev.idion.kotlinuint.uint.UintTest

이것저것 해봤는데 안돼서 코틀린으로는 포기하고 자바로 변경...

2022-04-24 01:47:45.967 DEBUG 68713 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : GET "/uint", parameters={}
2022-04-24 01:47:45.971 DEBUG 68713 --- [nio-8080-exec-1] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to dev.idion.kotlinuint.uint.UintTestController#all()
2022-04-24 01:47:46.081 DEBUG 68713 --- [nio-8080-exec-1] org.hibernate.SQL                        : 
    select
        uinttest0_.id as id1_0_,
        uinttest0_.mau as mau2_0_ 
    from
        uint_test uinttest0_
2022-04-24 01:47:46.109  INFO 68713 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장된 값: null
2022-04-24 01:47:46.110  INFO 68713 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티로 반환될 값: null
2022-04-24 01:47:46.110  INFO 68713 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장된 값: 2147483648
2022-04-24 01:47:46.111  INFO 68713 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티로 반환될 값: 2147483648
2022-04-24 01:47:46.111  INFO 68713 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장된 값: 2147483648
2022-04-24 01:47:46.111  INFO 68713 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티로 반환될 값: 2147483648
2022-04-24 01:47:46.111  INFO 68713 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : DB에 저장된 값: 2147483648
2022-04-24 01:47:46.111  INFO 68713 --- [nio-8080-exec-1] dev.idion.kotlinuint.uint.UIntConverter  : 엔티티로 반환될 값: 2147483648
2022-04-24 01:47:46.187 DEBUG 68713 --- [nio-8080-exec-1] m.m.a.RequestResponseBodyMethodProcessor : Using 'application/json', given [*/*] and supported [application/json, application/*+json, application/json, application/*+json]
2022-04-24 01:47:46.188 DEBUG 68713 --- [nio-8080-exec-1] m.m.a.RequestResponseBodyMethodProcessor : Writing [[dev.idion.kotlinuint.uint.UintTest@a0e311f, dev.idion.kotlinuint.uint.UintTest@3af9f2bb, dev.idion. (truncated)...]
2022-04-24 01:47:46.295 DEBUG 68713 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed 200 OK

결과

[
  {
    "id": 1,
    "mau": null
  },
  {
    "id": 2,
    "mau": 2147483648
  },
  {
    "id": 3,
    "mau": 2147483648
  },
  {
    "id": 4,
    "mau": 2147483648
  }
]

결론

Converter 를 이용한 방법으로 값을 다룰 수는 있다. 하지만 validate 옵션을 꺼야하는 단점이 존재한다.

p.s.

kotlin jpa 플러그인이 혼자 오동작한다. no args constructor도 안만들어주고, open도 안해준다... 나한테 왜그래!!

갓바의 힘으로 PoC를 마무리 할 수 있게되었다.