안녕하세요. 강의 후 개인적으로 학습 시 나타나는 NPE관련 질문드립니다.

Question

안녕하세요! 강의를 완강 후 혼자 프로젝트를 진행하다 도서 대출 코드를 보고 비슷하게 구현한 사용자가 채용공고를 지원하는 메소드를 호출시 테스트 코드에서 NPE가 발생하는데 혹시 이유를 알 수 있을까요? 여러가지 서칭해봐도 해결이 안되서 질문드립니다... ㅠㅠ 회원entity @Getter @NoArgsConstructor(access = AccessLevel.PROTECTED) @Table(name = "users") @Entity public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "user_id") private Long id; private String name; @OneToMany(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true) private List applyHistory = new ArrayList<>(); public void applyCompany(JobPosting jobPosting) { this.applyHistory.add(new ApplyHistory(this, jobPosting)); } @Builder private User(Long id, String name, List applyHistory) { this.id = id; this.name = name; this.applyHistory = applyHistory; } } ApplyHistory entity(JobPosting과 user객체가 N:M 매핑해주는 entity) @Getter @NoArgsConstructor(access = AccessLevel.PROTECTED) @Table(name = "apply_history") @Entity public class ApplyHistory { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "apply_history_id") private Long id; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "user_id") private User user; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "job_posting_id") private JobPosting jobPosting; public ApplyHistory(User user, JobPosting jobPosting) { this.user = user; this.jobPosting = jobPosting; } } JobPosting Entity @Getter @NoArgsConstructor(access = AccessLevel.PROTECTED) @Table(name = "job_posting") @Entity public class JobPosting { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "job_posting_id") private Long id; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "company_id") private Company company; @Column(name = "posting_position") private String position; private int compensation; //채용보상금 @Column(name = "posting_details") private String postingDetails; @Column(name = "technology_used") private String technologyUsed; @Builder private JobPosting(Company company, String position, int compensation, String postingDetails, String technologyUsed) { this.company = company; this.position = position; this.compensation = compensation; this.postingDetails = postingDetails; this.technologyUsed = technologyUsed; } public void updateJobPosting(String position, int compensation, String postingDetails, String technologyUsed) { this.position = position; this.compensation = compensation; this.postingDetails = postingDetails; this.technologyUsed = technologyUsed; } } applyService @RequiredArgsConstructor @Service public class ApplyService { private final JobPostingRepository jobPostingRepository; private final UserRepository userRepository; private final ApplyHistoryRepository userJobPostingRepository; @Transactional public void applyCompany(ApplyCompanyRequest request) { // 1. 채용공고 정보 찾기 JobPosting jobPosting = jobPostingRepository.findById(request.getJobPostingId()) .orElseThrow(() -> new ResourceNotFoundException("jobPosting", request.getJobPostingId())); // 2. 유저 정보 가져오기 User user = userRepository.findById(request.getUserId()) .orElseThrow(() -> new ResourceNotFoundException("user", request.getUserId())); // 3. 지원 유무 확인 // 3-1. 지원 중이면 예외 발생 if (userJobPostingRepository.existsByJobPostingAndUser(jobPosting, user)) { throw new IllegalArgumentException("이미 지원하신 회사입니다."); } user.applyCompany(jobPosting); } } 리퀘스트 @Getter @Setter public class ApplyCompanyRequest { private Long jobPostingId; private Long userId; } 서비스 테스트 코드 @SpringBootTest class ApplyServiceTest { @Autowired JobPostingService jobPostingService; @Autowired ApplyService applyService; @Autowired JobPostingRepository jobPostingRepository; @Autowired UserRepository userRepository; @Autowired ApplyHistoryRepository applyHistoryRepository; @Autowired CompanyRepository companyRepository; @AfterEach void tearDown() { applyHistoryRepository.deleteAllInBatch(); jobPostingRepository.deleteAllInBatch(); userRepository.deleteAllInBatch(); companyRepository.deleteAllInBatch(); } @DisplayName("사용자는 채용 공고를 지원 할 수 있다.") @Test @Transactional void applyCompany() { //given User user = User.builder() .id(1L) .name("jw") .build(); User savedUser = userRepository.save(user); Company company = Company.builder() .name("company1") .country(Country.KOREA) .city(City.SEOUL) .build(); Company savedCompany = companyRepository.save(company); JobPosting jobPosting = JobPosting.builder() .company(savedCompany) .position("백엔드") .postingDetails("백엔드 개발자 채용합니다.") .compensation(500000) .technologyUsed("Java") .build(); JobPosting savedJobPosting = jobPostingRepository.save(jobPosting); ApplyCompanyRequest request = new ApplyCompanyRequest(); request.setUserId(savedUser.getId()); request.setJobPostingId(savedJobPosting.getId()); //when applyService.applyCompany(request); //then } } -> 이부분에서 applyCompany(request) 호출 시 NPE가 발생합니다. java.lang.NullPointerException at com.wanted.findjob.domain.user.User.applyCompany(User.java:36) at com.wanted.findjob.api.service.ApplyService.applyCompany(ApplyService.java:39) at com.wanted.findjob.api.service.ApplyService$$FastClassBySpringCGLIB$$2f4064b0.invoke() at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:792) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:762) at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:762) at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:707) at com.wanted.findjob.api.service.ApplyService$$EnhancerBySpringCGLIB$$81701d47.applyCompany() at com.wanted.findjob.api.service.ApplyServiceTest.applyCompany(ApplyServiceTest.java:83) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:725) at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60) at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131) at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149) at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140) at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84) at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115) at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105) at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106) at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64) at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45) at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37) at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104) at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$7(TestMethodTestDescriptor.java:214) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:210) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:66) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:151) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141) at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138) at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95) at java.base/java.util.ArrayList.forEach(ArrayList.java:1540) at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141) at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138) at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95) at java.base/java.util.ArrayList.forEach(ArrayList.java:1540) at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141) at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137) at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139) at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138) at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95) at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35) at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57) at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67) at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52) at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114) at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86) at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86) at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53) at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:57) at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38) at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:232) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:55) 테스트코드가 아닌 직접 서버를 작동해서 api를 호출 시 정상적으로 db에 들어가는 걸 볼 수 있는데 어디가 문제 인지를 모르겠습니다.. ㅠ

javabase · Answer

User Entity에서 Bulider패턴 사용시 List<ApplyHistory> applyHistory 초기화 부분문제 때문에 일어난 거였습니다.. 혹시라도 비슷한 경험을 하시는 분들을 위해 질문은 남겨 놓을게요 감사합니다!

lannstark · Answer

안녕하세요 정우님!! 와우~ 해결하셨군요!! 다행입니다~ 😊   추가적으로 테스트를 하다가 뭔가 동작이 이상하면 중간에 System.out.println()을 사용하시거나 (약간 비추천) IntelliJ 디버깅 기능을 활용하셔서 (매우 추천) https://youtu.be/OHrLRg150As?si=XWb73Rvjo4rcShHw DB의 데이터를 확인해보실 수 있습니다.   예를 들어, 테스트 중간에 ApplyHistoryRepository에 접근해보는 것이죠!   혹시나 또 어려운 점 있으시면 편하게 질문 남겨주세요. 감사합니다! 🙇