如何避免javax.persistence.EntityExistsException：具有相同標識符的不同對象？

我有一個小問題項目，就像測驗API一樣。當我嘗試保存複雜對象（考試）時，hibernate拋出EntityExistsException。我使用dto（CreateExamRequestDto）獲得REST請求，然後將此dto映射到實體並使用Spring Data JPA進行保存。如何避免javax.persistence.EntityExistsException：具有相同標識符的不同對象？

這裏是我的實體類：

EXAM實體：

@Entity 
@Table(name = "exams", uniqueConstraints = {@UniqueConstraint(columnNames = { 
     "name", 
     "category_id" 
})}) 
public class Exam extends AbstractEntity { 
    @Id 
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "exams_seq_gen") 
    @SequenceGenerator(name = "exams_seq_gen", sequenceName = "exams_id_seq") 
    @Column(name = "id") 
    private Integer id; 
    @Column(name = "name", nullable = false) 
    private String name; 
    @ManyToOne 
    @JoinColumn(name = "category_id", nullable = false) 
    private Category category; 
    @ManyToOne 
    @JoinColumn(name = "owner_id", nullable = false) 
    private User owner; 
    @OneToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST}) 
    private List<Section> sections; 
    @Column(name = "target_score", nullable = false) 
    private Integer targetScore; 
    @OneToMany() 
    private List<ExamResult> results; 

    @Transient 
    private ExamResult result; 

    //public constructor, getters, setters, hashcode and equals 
}

部分實體：

@Entity 
@Table(name = "exam_sections", uniqueConstraints = @UniqueConstraint(columnNames = { 
     "name", 
     "exam_id" 
})) 
public class Section extends AbstractEntity { 
    @Id 
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "exam_sections_seq_gen") 
    @SequenceGenerator(name = "exam_sections_seq_gen", sequenceName = "exam_sections_id_seq") 
    @Column(name = "id") 
    private Integer id; 
    @Column(name = "name", nullable = false) 
    private String name; 
    @Column(name = "question_weight", nullable = false) 
    private Integer questionWeight; 
    @Column(name = "target_questions", nullable = false) 
    private Integer targetQuestions; 
    @OneToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST}) 
    private List<Question> questions; 
    @ManyToOne 
    @JoinColumn(name = "exam_id", nullable = false) 
    private Exam exam; 

    //public constructor, getters, setters, hashcode and equals 
}

問題實體：

@Entity 
@Table(name = "questions") 
public class Question extends AbstractEntity { 
    @Id 
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "questions_seq_gen") 
    @SequenceGenerator(name = "questions_seq_gen", sequenceName = "questions_id_seq") 
    @Column(name = "id") 
    private Integer id; 
    @Column(name = "text", nullable = false) 
    private String text; 
    @Column(name = "type", nullable = false) 
    @Enumerated(EnumType.STRING) 
    private QuestionType type; 
    @OneToMany(cascade = {CascadeType.MERGE, CascadeType.PERSIST}) 
    private List<Answer> answers; 
    @ManyToOne 
    @JoinColumn(name = "section_id") 
    private Section section; 

    //public constructor, getters, setters, hashcode and equals 
}

答案實體：

@Entity 
@Table(name = "answers") 
public class Answer extends AbstractEntity { 
    @Id 
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "answers_seq_gen") 
    @SequenceGenerator(name = "answers_seq_gen", sequenceName = "answers_id_seq") 
    @Column(name = "id") 
    private Integer id; 
    @Column(name = "text", nullable = false) 
    private String text; 
    @Column(name = "correct", nullable = false) 
    private Boolean correct; 
    @ManyToOne 
    @JoinColumn(name = "question_id", nullable = false) 
    private Question question; 

    //public constructor, getters, setters, hashcode and equals 
}

和代碼保存了一切：

@Override 
@Transactional 
public ExamShortDto createExam(CreateExamRequestDto request) { 
    Exam exam = examMapper.mapToEntity(request, user); 
    exam = examRepository.save(exam);    <<----- HERE 

    return examMapper.mapToShortDto(exam); 
}

在尖線我有一個異常：

2017年9月5日17：24：12.278錯誤14024 --- [nio-8080-exec-1] osbwservlet.support.ErrorPageFilter：由於異常[由於請求[/ api/exam]轉發到錯誤頁面[具有相同標識符值的不同對象已與會話相關聯：[org。 yvasylchuk.testit.domain.entity.exam.Answer＃191]。嵌套異常是javax.persistence.EntityExistsException：用相同的標識符值的不同的對象已經與會話相關聯：[org.yvasylchuk.testit.domain.entity.exam.Answer＃191]]

org.springframework.dao.DataIntegrityViolationException: A different object with the same identifier value was already associated with the session : [org.yvasylchuk.testit.domain.entity.exam.Answer#191]; nested exception is javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [org.yvasylchuk.testit.domain.entity.exam.Answer#191] 
    at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:395) ~[spring-orm-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:226) ~[spring-orm-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:499) ~[spring-orm-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59) ~[spring-tx-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:216) ~[spring-tx-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:153) ~[spring-tx-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:134) ~[spring-data-jpa-2.0.0.RC2.jar:na] 
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:61) ~[spring-data-commons-2.0.0.RC2.jar:na] 
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185) ~[spring-aop-5.0.0.RC3.jar:5.0.0.RC3] 
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) ~[spring-aop-5.0.0.RC3.jar:5.0.0.RC3] 
    at com.sun.proxy.$Proxy130.save(Unknown Source) ~[na:na] 
    at org.yvasylchuk.testit.service.exam.impl.ExamFacadeImpl.createExam(ExamFacadeImpl.java:143) ~[classes/:0.0.1-SNAPSHOT] 

    ...... 

Caused by: javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [org.yvasylchuk.testit.domain.entity.exam.Answer#191] 
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:116) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:155) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:162) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:771) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener$1.cascade(JpaPersistEventListener.java:80) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:458) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:383) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:193) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:491) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:423) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:386) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:193) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:126) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:445) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:281) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:182) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:125) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:67) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:189) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:132) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:771) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener$1.cascade(JpaPersistEventListener.java:80) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:458) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:383) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:193) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:491) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:423) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:386) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:193) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:126) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:445) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:281) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:182) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:125) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:67) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:189) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:132) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:771) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener$1.cascade(JpaPersistEventListener.java:80) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:458) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:383) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:193) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:491) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:423) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:386) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:193) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:126) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:445) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:281) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:182) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:125) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:67) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:189) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:132) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:58) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:780) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:765) ~[hibernate-core-5.2.10.Final.jar:5.2.10.Final] 
    ...

解：

我只是在回答實體從改變一個行：

@Id 
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "answers_seq_gen") 
HERE -->> @SequenceGenerator(name = "answers_seq_gen", sequenceName = "answers_id_seq") 
@Column(name = "id") 
private Integer id;

到：

@Id 
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "answers_seq_gen") 
HERE -->> @SequenceGenerator(name = "answers_seq_gen", sequenceName = "answers_id_seq", allocationSize = 200) 
@Column(name = "id") 
private Integer id;

來源

2017-09-05 Yurii Vasilchuk

做你'id'（S）列在你的數據庫已經啓用AUTO_INCREMENT或類似的東西？ – Shirkam

真正發生了什麼：因爲你在級聯你的答案，並且由於關係是OneToMany，所以你可能有很多答案超過了分配尺寸的缺省值，序列發生器具有屬性分配尺寸，它指示交易中可能的數量會增加，所以如果超出限制，您的ID最終會重複。

解決方法：您可以將發電機切換到AUTO或increate分配大小

來源

2017-09-05 15:12:11

謝謝，你節省了我很多時間！ –

如何避免javax.persistence.EntityExistsException：具有相同標識符的不同對象？

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