인프런 커뮤니티 질문&답변

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[질문 템플릿]
1. 강의 내용과 관련된 질문인가요? (예/아니오)
2. 인프런의 질문 게시판과 자주 하는 질문에 없는 내용인가요? (예/아니오)
3. 질문 잘하기 메뉴얼을 읽어보셨나요? (예/아니오)

[질문 내용]
여기에 질문 내용을 남겨주세요.

UsernameOnly 인터페이스 타입과 지네릭스 타입으로 결과는 문제 없이 동작하지만

UsernameOnlyDto 타입으로 결과 값을 받으려고 findProjectionsByUsername를 호출하면

type mismatch 오류가 생깁니다.

Specified result type [study.datajpa.dto.UsernameOnlyDto] did not match Query selection type [study.datajpa.entity.Member] - multiple selections: use Tuple or array

List<UsernameOnlyDto> result = memberRepository.findProjectionsByUsername("m1");

package study.datajpa.dto;

public class UsernameOnlyDto {
    private final String username;

    public UsernameOnlyDto(String username) {
        this.username = username;
    }

    public String getUsername() {
        return username;
    }
}

// List<UsernameOnly> findProjectionsByUsername(@Param("username") String username);

 List<UsernameOnlyDto> findProjectionsByUsername(@Param("username") String username);

<T> List<T> findProjectionsByUsername(@Param("username") String username, Class<T> type);

org.springframework.orm.jpa.JpaSystemException: Specified result type [study.datajpa.dto.UsernameOnlyDto] did not match Query selection type [study.datajpa.entity.Member] - multiple selections: use Tuple or array

at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:341)

at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:241)

at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:560)

at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61)

at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:343)

at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:160)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184)

at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:136)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184)

at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:223)

at jdk.proxy2/jdk.proxy2.$Proxy149.findProjectionsByUsername(Unknown Source)

at study.datajpa.repository.MemberRepositoryTest.projections(MemberRepositoryTest.java:403)

at java.base/java.lang.reflect.Method.invoke(Method.java:568)

at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

Suppressed: org.springframework.transaction.UnexpectedRollbackException: Transaction silently rolled back because it has been marked as rollback-only

at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:804)

at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:758)

at org.springframework.test.context.transaction.TransactionContext.endTransaction(TransactionContext.java:135)

at org.springframework.test.context.transaction.TransactionalTestExecutionListener.afterTestMethod(TransactionalTestExecutionListener.java:272)

at org.springframework.test.context.TestContextManager.afterTestMethod(TestContextManager.java:488)

at org.springframework.test.context.junit.jupiter.SpringExtension.afterEach(SpringExtension.java:275)

... 2 more

Caused by: org.hibernate.query.QueryTypeMismatchException: Specified result type [study.datajpa.dto.UsernameOnlyDto] did not match Query selection type [study.datajpa.entity.Member] - multiple selections: use Tuple or array

at org.hibernate.query.sqm.internal.SqmUtil.throwQueryTypeMismatchException(SqmUtil.java:1272)

at org.hibernate.query.sqm.internal.SqmUtil.verifyResultType(SqmUtil.java:1209)

at org.hibernate.query.sqm.internal.SqmUtil.verifySelectionType(SqmUtil.java:1159)

at org.hibernate.query.sqm.internal.SqmUtil.verifySingularSelectionType(SqmUtil.java:1114)

at org.hibernate.query.sqm.internal.SqmUtil.checkQueryReturnType(SqmUtil.java:1088)

at org.hibernate.query.sqm.internal.SqmUtil.checkQueryReturnType(SqmUtil.java:1049)

at org.hibernate.query.sqm.internal.SqmUtil.validateQueryReturnType(SqmUtil.java:1040)

at org.hibernate.query.sqm.tree.select.SqmSelectStatement.validateResultType(SqmSelectStatement.java:153)

at org.hibernate.query.sqm.internal.QuerySqmImpl.<init>(QuerySqmImpl.java:240)

at org.hibernate.internal.AbstractSharedSessionContract.createCriteriaQuery(AbstractSharedSessionContract.java:1483)

at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:1443)

at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:143)

at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)

at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.base/java.lang.reflect.Method.invoke(Method.java:568)

at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:320)

at jdk.proxy2/jdk.proxy2.$Proxy136.createQuery(Unknown Source)