[Springboot] "Could not create query for public abstract java.util.Optional " 오류 수정

안녕하세요 오늘은 웹 크롤링을 이용한 배당금 프로젝트 를 진행하던 도중 마주친 Could not create query for public abstract java.util.Optional ~~ 오류 해결에 대해 기록을 남겨보려고 합니다 👨‍💻

해당 소스가 궁금하시다면 웹 크롤링을 이용한 배당금 프로젝트💰 을 참고해주세요!
먼저 오류와 관련된 코드 부분부터 살펴보겠습니다 ❗️

👨‍🔧 관련 코드

// 회원 정보를 가지는 Member(회원) 엔티티 클래스
@Slf4j
@Getter
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Entity(name = "MEMBERS")
public class MemberEntity extends BaseEntity implements UserDetails {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id", nullable = false)
    private Long id;

    @Column(name = "USER_NAME", nullable = false, length = 50)
    private String userName;

    @Column(name = "PASSWORD", nullable = false, length = 50)
    private String password;

    @Enumerated(EnumType.STRING)
    private Authority authority;

    @Override
    public Collection<? extends GrantedAuthority> getAuthorities() {
        return null;
    }

    @Override
    public String getUsername() {
        return null;
    }

    @Override
    public boolean isAccountNonExpired() {
        return false;
    }

    @Override
    public boolean isAccountNonLocked() {
        return false;
    }

    @Override
    public boolean isCredentialsNonExpired() {
        return false;
    }

    @Override
    public boolean isEnabled() {
        return false;
    }
}

// Member(회원) 엔티티를 저장할 MemberRepository 
@Repository 
public interface MemberRepository extends JpaRepository<MemberEntity, Long> {
    Optional<MemberEntity> findByUsername(String userName); // 회원 이름을 통해 회원 엔티티를 찾는 메소드

    boolean existsByUsername(String userName); // 회원가입을 할때 이미 존재하는 회원인지 확인하기 위한 메소드
}

두개의 코드는 프로젝트를 진행하면서 Member 엔티티를 나타내고 저장하기 위한 코드입니다.
MemberRepository 인터페이스에는 두개의 메소드가 구현되어 있습니다.
해당 메소드는 회원 가입 및 로그인 로직에서 필수적인 역할을 하는 메소드입니다 👨‍💻
해당 코드를 작성하고 Spring 어플리케이션을 실행시켰습니다 🔥
그러나...!!

	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1804) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:936) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:918) ~[spring-context-5.3.25.jar:5.3.25]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.25.jar:5.3.25]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:147) ~[spring-boot-2.7.9.jar:2.7.9]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:731) ~[spring-boot-2.7.9.jar:2.7.9]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:408) ~[spring-boot-2.7.9.jar:2.7.9]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:307) ~[spring-boot-2.7.9.jar:2.7.9]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1303) ~[spring-boot-2.7.9.jar:2.7.9]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1292) ~[spring-boot-2.7.9.jar:2.7.9]
	at com.example.dividendproject.DividendProjectApplication.main(DividendProjectApplication.java:16) ~[main/:na]
Caused by: org.springframework.data.repository.query.QueryCreationException: Could not create query for public abstract java.util.Optional com.example.dividendproject.domain.repository.MemberRepository.findByUsername(java.lang.String); Reason: Failed to create query for method public abstract java.util.Optional com.example.dividendproject.domain.repository.MemberRepository.findByUsername(java.lang.String)! Unable to locate Attribute  with the the given name [username] on this ManagedType [com.example.dividendproject.domain.entity.BaseEntity]; nested exception is java.lang.IllegalArgumentException: Failed to create query for method public abstract java.util.Optional com.example.dividendproject.domain.repository.MemberRepository.findByUsername(java.lang.String)! Unable to locate Attribute  with the the given name [username] on this ManagedType [com.example.dividendproject.domain.entity.BaseEntity]
	at org.springframework.data.repository.query.QueryCreationException.create(QueryCreationException.java:101) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.lookupQuery(QueryExecutorMethodInterceptor.java:107) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.lambda$mapMethodsToQuery$1(QueryExecutorMethodInterceptor.java:95) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) ~[na:na]
	at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133) ~[na:na]
	at java.base/java.util.Collections$UnmodifiableCollection$1.forEachRemaining(Collections.java:1061) ~[na:na]
	at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1845) ~[na:na]
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) ~[na:na]
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) ~[na:na]
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921) ~[na:na]
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:na]
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682) ~[na:na]
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.mapMethodsToQuery(QueryExecutorMethodInterceptor.java:97) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.lambda$new$0(QueryExecutorMethodInterceptor.java:87) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at java.base/java.util.Optional.map(Optional.java:260) ~[na:na]
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.<init>(QueryExecutorMethodInterceptor.java:87) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:365) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.lambda$afterPropertiesSet$5(RepositoryFactoryBeanSupport.java:323) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.util.Lazy.getNullable(Lazy.java:231) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.util.Lazy.get(Lazy.java:115) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:329) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:144) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1863) ~[spring-beans-5.3.25.jar:5.3.25]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1800) ~[spring-beans-5.3.25.jar:5.3.25]
	... 16 common frames omitted
Caused by: java.lang.IllegalArgumentException: Failed to create query for method public abstract java.util.Optional com.example.dividendproject.domain.repository.MemberRepository.findByUsername(java.lang.String)! Unable to locate Attribute  with the the given name [username] on this ManagedType [com.example.dividendproject.domain.entity.BaseEntity]
	at org.springframework.data.jpa.repository.query.PartTreeJpaQuery.<init>(PartTreeJpaQuery.java:96) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:119) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateIfNotFoundQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:259) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$AbstractQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:93) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.lookupQuery(QueryExecutorMethodInterceptor.java:103) ~[spring-data-commons-2.7.8.jar:2.7.8]
	... 38 common frames omitted
Caused by: java.lang.IllegalArgumentException: Unable to locate Attribute  with the the given name [username] on this ManagedType [com.example.dividendproject.domain.entity.BaseEntity]
	at org.hibernate.metamodel.model.domain.internal.AbstractManagedType.checkNotNull(AbstractManagedType.java:148) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at org.hibernate.metamodel.model.domain.internal.AbstractManagedType.getAttribute(AbstractManagedType.java:119) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at org.hibernate.metamodel.model.domain.internal.AbstractManagedType.getAttribute(AbstractManagedType.java:117) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at org.hibernate.metamodel.model.domain.internal.AbstractManagedType.getAttribute(AbstractManagedType.java:44) ~[hibernate-core-5.6.15.Final.jar:5.6.15.Final]
	at org.springframework.data.jpa.repository.query.QueryUtils.requiresOuterJoin(QueryUtils.java:822) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.QueryUtils.toExpressionRecursively(QueryUtils.java:763) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.QueryUtils.toExpressionRecursively(QueryUtils.java:742) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.QueryUtils.toExpressionRecursively(QueryUtils.java:738) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.JpaQueryCreator$PredicateBuilder.getTypedPath(JpaQueryCreator.java:394) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.JpaQueryCreator$PredicateBuilder.build(JpaQueryCreator.java:317) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.JpaQueryCreator.toPredicate(JpaQueryCreator.java:217) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.JpaQueryCreator.create(JpaQueryCreator.java:125) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.JpaQueryCreator.create(JpaQueryCreator.java:60) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.query.parser.AbstractQueryCreator.createCriteria(AbstractQueryCreator.java:120) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.query.parser.AbstractQueryCreator.createQuery(AbstractQueryCreator.java:96) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.repository.query.parser.AbstractQueryCreator.createQuery(AbstractQueryCreator.java:82) ~[spring-data-commons-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.PartTreeJpaQuery$QueryPreparer.<init>(PartTreeJpaQuery.java:217) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.PartTreeJpaQuery$CountQueryPreparer.<init>(PartTreeJpaQuery.java:348) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	at org.springframework.data.jpa.repository.query.PartTreeJpaQuery.<init>(PartTreeJpaQuery.java:91) ~[spring-data-jpa-2.7.8.jar:2.7.8]
	... 42 common frames omitted```

이렇게 긴 오류 메세지가 실행 콘솔에 나타납니다...🥹
당황하지 않고 차근차근 읽어보겠습니다.
가장 눈에 띄는 부분은 Could not create query for public abstract java.util.Optional com.example.dividendproject.domain.repository.MemberRepository.findByUsername(java.lang.String); Reason: Failed to create query for method public abstract java.util.Optional com.example.dividendproject.domain.repository.MemberRepository.findByUsername(java.lang.String)! Unable to locate Attribute with the the given name [username] on this ManagedType [com.example.dividendproject.domain.entity.BaseEntity]; nested exception is java.lang.IllegalArgumentException: Failed to create query for method public abstract java.util.Optional com.example.dividendproject.domain.repository.MemberRepository.findByUsername(java.lang.String)! Unable to locate Attribute with the the given name [username] on this ManagedType [com.example.dividendproject.domain.entity.BaseEntity] 부분이였습니다.

즉 MemberRepository 에서 구현된 메소드 명[username]에 어떠한 오류가 존재한다는 것을 알게되었고 구글링을 통해 관련 오류를 찾아보았습니다 🧑🏼‍💻

👨‍🔧 해결방안

해당 오류는 메소드 명을 자바의 명명법인 카멜 표기법 을 따르지 않았기 때문에 발생합니다.
천천히 MemberRepository 코드를 살펴보니 findusername existsByusername 의 이름에서 카멜 표기법 이 적용되지 않은 것을 확인할 수 있습니다 👨‍🔧

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참고

[spring boot jpa] Failed to create query for method public abstract java.util.List 오류