Hibernate从子实体获取父ID

【问题标题】：Hibernate get parent's id from child entityHibernate从子实体获取父ID
【发布时间】：2012-11-10 16:09:10
【问题描述】：

很多人都发布了非常相似的问题，但我似乎无法找到解决我的情况的问题。

我有一个父实体Dnar 和一个子实体WorkLocationSuburb。一个Dnar 具有一对多的WorkLocationSuburbs。

通常，我会这样定义这种关系：

孩子

@Entity
@Table(name = "req_work_suburb", schema = SCHEMA)
public class WorkLocationSuburb {

  @Id
  @GeneratedValue(generator = "req_work_suburb_seq")
  @GenericGenerator(strategy="sequence", name="req_work_suburb_seq", parameters={@Parameter(name="sequence", value=SCHEMA+".req_work_suburb_seq")})
  @Column(name = "id", nullable = false)
  private Long id;

  @Column(name="suburb", length=255, nullable=false)
  private String suburb;

  //remainder omitted
}

父级

@Entity
@Table(name = "req_dnar", schema = SCHEMA)
@Inheritance(strategy = JOINED)
@DiscriminatorColumn(name = "form_type", discriminatorType = STRING, length = 64)
public abstract class Dnar {

  @Id
  @GeneratedValue(generator = "req_dnar_seq")
  @GenericGenerator(strategy = "sequence", name = "req_dnar_seq", parameters = { @Parameter(name = "sequence", value = SCHEMA + ".req_dnar_seq") })
  @Column(name = C_DNAR_ID, nullable = false)
  private Long dnarId;

  @Column(name = "original_id")
  private Long originalId;


  @OneToMany(cascade = ALL, fetch = EAGER, orphanRemoval=true)
  @JoinColumn(name = "dnar_id", nullable=false)
  private Set<WorkLocationSuburb> workLocationSuburbs;

  //remainder omitted
}

上面的例子有效，当我手动查询req_work_suburb 表时，我可以看到它有一个dnar_id 列并且该列被正确填充。一切顺利，到目前为止！

在一些查询代码中，我创建了一个依赖于req_work_suburb.dnar_id 值的条件查询：

  private static Specification<SubmittedDnarSummary> suburbIs(final String suburb) {
    return new Specification<SubmittedDnarSummary>(){
      @Override
      public Predicate toPredicate(Root<SubmittedDnarSummary> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
        Subquery<Long> subquery = query.subquery(Long.class);
        Root<WorkLocationSuburb> suburbRoot = subquery.from(WorkLocationSuburb.class);
        return cb.in(root.get("dnarId")).value(subquery.select(suburbRoot.<Long>get("dnarId")).where(cb.equal(suburbRoot.get("suburb"), suburb)));
      }
    };
  }

执行上述操作时，出现以下异常：

org.springframework.dao.InvalidDataAccessApiUsageException: Unable to resolve attribute [dnarId] against path; nested exception is java.lang.IllegalArgumentException: Unable to resolve attribute [dnarId] against path
         at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:301)
         at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:106)
         at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:403)
         at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:58)
         at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)
         at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:163)
         at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
         at org.springframework.data.jpa.repository.support.LockModeRepositoryPostProcessor$LockModePopulatingMethodIntercceptor.invoke(LockModeRepositoryPostProcessor.java:91)
         at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
         at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:90)
         at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
         at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
         at $Proxy253.findAll(Unknown Source)
         at au.com.wpcorp.sys.dnar.spring.manager.impl.SearchManagerImpl.search(SearchManagerImpl.java:66)
         at au.com.wpcorp.sys.dnar.spring.mvc.controller.search.DnarSearchController.results(DnarSearchController.java:97)
         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
         at java.lang.reflect.Method.invoke(Method.java:597)
         at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
         at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
         at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
         at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
         at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
         at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
         at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
         at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
         at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
         at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
         at javax.servlet.http.HttpServlet.service(HttpServlet.java:668)
         at javax.servlet.http.HttpServlet.service(HttpServlet.java:770)
         at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
         at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
         at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
         at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
         at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
         at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
         at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
         at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
         at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
         at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
         at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
         at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
         at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
         at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
         at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
         at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
         at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
         at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
         at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
         at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
         at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
         at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
         at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
         at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.IllegalArgumentException: Unable to resolve attribute [dnarId] against path
         at org.hibernate.ejb.criteria.path.AbstractPathImpl.unknownAttribute(AbstractPathImpl.java:118)
         at org.hibernate.ejb.criteria.path.AbstractPathImpl.locateAttribute(AbstractPathImpl.java:223)
         at org.hibernate.ejb.criteria.path.AbstractPathImpl.get(AbstractPathImpl.java:194)
         at au.com.wpcorp.sys.dnar.spring.manager.impl.SearchManagerImpl$3.toPredicate(SearchManagerImpl.java:141)
         at org.springframework.data.jpa.repository.support.SimpleJpaRepository.applySpecificationToCriteria(SimpleJpaRepository.java:480)
         at org.springframework.data.jpa.repository.support.SimpleJpaRepository.getQuery(SimpleJpaRepository.java:436)
         at org.springframework.data.jpa.repository.support.SimpleJpaRepository.getQuery(SimpleJpaRepository.java:421)
         at org.springframework.data.jpa.repository.support.SimpleJpaRepository.findAll(SimpleJpaRepository.java:303)
         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
         at java.lang.reflect.Method.invoke(Method.java:597)
         at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:334)
         at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:319)
         at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
         at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
         at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
         at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:155)
         ... 49 more

它似乎失败了，因为 Hibernate 在 WorkLocationSuburb 上找不到名为 dnarId 的属性。我的问题是，如何在不让 Hibernate 抱怨其他问题的情况下将此信息添加到 WorkLocationSuburb？看来我需要一些代码，例如：

@Entity
@Table(name = "req_work_suburb", schema = SCHEMA)
public class WorkLocationSuburb {

  @Id
  @GeneratedValue(generator = "req_work_suburb_seq")
  @GenericGenerator(strategy="sequence", name="req_work_suburb_seq", parameters={@Parameter(name="sequence", value=SCHEMA+".req_work_suburb_seq")})
  @Column(name = "id", nullable = false)
  private Long id;

  @Column(name="suburb", length=255, nullable=false)
  private String suburb;

  @Column(name="dnar_id", nullable=false)  // column definition added here
  private Long dnarId;

  //remainder omitted
}

有谁知道我怎样才能使上述附加列正常工作？此列必须自动填充父母的dnarId。

谢谢， 穆尔。

更新了 JB Nizet 的建议

我的代码现在是这样的：

孩子

@Entity
@Table(name = "req_work_suburb", schema = SCHEMA)
public class WorkLocationSuburb {

  @Id
  @GeneratedValue(generator = "req_work_suburb_seq")
  @GenericGenerator(strategy="sequence", name="req_work_suburb_seq", parameters={@Parameter(name="sequence", value=SCHEMA+".req_work_suburb_seq")})
  @Column(name = "id", nullable = false)
  private Long id;

  @Column(name="suburb", length=255, nullable=false)
  private String suburb;

  @ManyToOne
  @JoinColumn(name="dnar_id", nullable=false)
  private Dnar dnar;

  //remainder omitted
}

父级

@Entity
@Table(name = "req_dnar", schema = SCHEMA)
@Inheritance(strategy = JOINED)
@DiscriminatorColumn(name = "form_type", discriminatorType = STRING, length = 64)
public abstract class Dnar {

  @Id
  @GeneratedValue(generator = "req_dnar_seq")
  @GenericGenerator(strategy = "sequence", name = "req_dnar_seq", parameters = { @Parameter(name = "sequence", value = SCHEMA + ".req_dnar_seq") })
  @Column(name = C_DNAR_ID, nullable = false)
  private Long dnarId;

  @Column(name = "original_id")
  private Long originalId;

  @OneToMany(cascade = ALL, fetch = EAGER, orphanRemoval=true, mappedBy="dnar")
  private Set<WorkLocationSuburb> workLocationSuburbs = new LinkedHashSet<WorkLocationSuburb>();


  @PostPersist
  void setChildRefs() {
    for (WorkLocationSuburb suburb : workLocationSuburbs) {
      suburb.setDnar(this);
    }
  }

  //remainder omitted
}

当我尝试保存附加了WorkLocationSuburb 的Dnar 时，我看到以下事件顺序：

  1. Dnar 被插入到数据库中
  2. @PostConstuct 被调用，WorkLocationSuburb 获得对父 Dnar 的引用。父 Dnar 已正确分配 ID。
  3. 尝试插入子 WorkLocationSuburb，但导致以下异常：org.hibernate.exception.ConstraintViolationException: ORA-01400: cannot insert NULL into ("DNAR"."REQ_WORK_SUBURB"."DNAR_ID")`

我仍然做错了什么？ :)

【问题讨论】：

    标签： java hibernate jpa-2.0 spring-data-jpa


    【解决方案1】：

    你只需要使关联是双向的：

    public class WorkLocationSuburb {
    @ManyToOne
    @JoinColumn
    private Dnar parentDnar;
    // ...
}

public class Dnar {
    @OneToMany(mappedBy = "parentDnar", ...)
    private Set<WorkLocationSuburb> suburbs;
    // ...
}

    请注意，在双向 OneToMany 关联中，关联的拥有方始终是多方（没有mappedBy 属性的一方）。这意味着 Hibernate 将只考虑 WorkLocationSuburb.parentDnar 字段来决定关联是否存在。因此，这意味着每次将郊区添加到 dnar 时，还必须设置郊区的 dnar 字段：

    public void addSuburb(WorkLocationSuburb suburb) {
    this.suburbs.add(suburb);
    suburb.setParentDnar(this);
}

    同样，如果从 dnar 中删除郊区，则应将郊区的 parentDnar 设置为 null。

    关于查询，您现在可以在查询中使用parentDnar 字段。请记住，JPA 查询始终对实体及其持久字段/属性起作用。永远不要在桌子及其列上。

    【讨论】：

    • 我已经尝试过你的建议，但 Hibernate 不明白如何在子实体上填充外键列。请问我错过了什么？哦，我将我尝试过的代码附加到上述问题中。
    • 尽量不要使用 PostPersist 挂钩来设置父 ID。我很确定您不应该在此类回调方法中修改实体。只需将其封装在您的实体或服务方法中即可。
    • 谢谢老兄，解决了！
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