在新线程的递归函数中分离实体？

irlmq6kh  于 2021-07-23  发布在  Java
关注(0)|答案(0)|浏览(242)

我在用 Spring Boot , Hibernate 以及 JavaMail 要创建的库 Email Client 项目（类似于 Thunderbird )为了我的学校项目。我很难坚持下去 Folder 实体。
以下是我拥有的大多数实体：
帐户

  1. @Getter
  2. @Setter
  3. @RequiredArgsConstructor
  4. @SuperBuilder
  5. @NoArgsConstructor
  6. @Entity
  7. @Table(name = "account")
  8. public class Account {
  10.     @Id
  11.     @GeneratedValue(strategy = GenerationType.IDENTITY)
  12.     @Column(name = "account_id", unique = true, nullable = false)
  13.     private int id;
  15.     @NonNull
  16.     @Column(nullable = false)
  17.     private String username;
  19.     @NonNull
  20.     @Column(nullable = false)
  21.     private String password;
  23.     @NonNull
  24.     @Builder.Default
  25.     @OneToMany(mappedBy = "account", orphanRemoval = true, cascade = CascadeType.ALL)
  26.     private Set<Folder> folders = new HashSet<>();
  28.     //There are other properties such as: smtpPort, inServerType(pop3 or imap), inServerPort...all primitives
  30. }

文件夹

  1. @Getter
  2. @Setter
  3. @SuperBuilder
  4. @NoArgsConstructor
  5. @Entity
  6. public class Folder {
  8.     @Id
  9.     @GeneratedValue(strategy = GenerationType.IDENTITY)
  10.     @Column(name = "folder_id", unique = true, nullable = false)
  11.     private int id;
  13.     @Column(name = "full_folder_name", nullable = true)
  14.     private String fullFolderName; //this is name of Folder on email server
  16.     @Column(name = "folder_name", nullable = true)
  17.     private String folderName;
  19.     @Column(name = "folder_url", nullable = true)
  20.     private String folderUrl;
  22.     @Builder.Default
  23.     @OneToMany(fetch = FetchType.EAGER, mappedBy = "parent", orphanRemoval = true)
  24.     private Set<Folder> children = new HashSet<Folder>();
  26.     @Builder.Default
  27.     @OneToMany(fetch = FetchType.EAGER, mappedBy = "folder", orphanRemoval = true)
  28.     @Column(nullable = false)
  29.     private Set<Message> messages = new HashSet<>();
  31.     @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
  32.     @JoinColumn(name = "parent_id", referencedColumnName = "folder_id", nullable = true)
  33.     private Folder parent;
  35.     @ManyToOne
  36.     private Account account;
  37. }

我希望能够从任何电子邮件服务器（如gmail、yahoo等）获取初始文件夹结构，并将该结构存储到我的数据库中（下一步是为每个服务器获取消息） Folder s。这个想法是从一个单独的线程获取文件夹结构，我不希望我的前端等待。我获取文件夹结构的代码工作正常，我获取所有文件夹层次结构，但仅从主线程获取。在我创建之后 Account 实体并将其持久化，只有这样我才能传递那个新引用（它确实有 Id )到以下助手方法。

  1. public void fetchInitialFolderStructure(@NonNull Account account)  {    
  2.         Runnable thread = () -> {
  3.             //Folder rootFolder = null;
  4.             try {
  5.                 Store store = getStore(account);
  7.                 if (store.isConnected()) {
  8.                     System.out.println("ok");
  9.                     javax.mail.Folder root = store.getDefaultFolder();
  10.                     final Folder rootFolder = folderService.save(Folder.builder()
  11.                             .fullFolderName(root.getFullName())
  12.                             .folderName(root.getName())
  13.                             .folderUrl(root.getURLName().toString())
  14.                             .children(new HashSet<Folder>())
  15.                             .messages(new HashSet<Message>())
  16.                             .account(account)
  17.                             .build());
  19.                     Arrays.stream(root.list("%")).forEach(jmailFolder -> {
  21.                         try {
  23.                             Folder levelFolder = Folder.builder()
  24.                                     .fullFolderName(jmailFolder.getFullName())
  25.                                     .folderName(jmailFolder.getName())
  26.                                     .folderUrl(jmailFolder.getURLName().toString())
  27.                                     .children(new HashSet<Folder>())
  28.                                     .messages(new HashSet<Message>())
  29.                                     .parent(rootFolder)
  30.                                     .account(account)
  31.                                     .build();
  32.                             levelFolder = folderService.save(levelFolder);
  33.                             dumpFolder(jmailFolder, levelFolder, account);
  34.                         } catch (MessagingException e) {
  35.                             e.printStackTrace();
  36.                         } 
  38.                     });
  40.                 } else {
  41.                     throw new IllegalArgumentException("Cannot connect to Store!");
  42.                 }
  44.                 store.close();
  45.             } catch (NoSuchProviderException e) {
  46.                 e.printStackTrace();
  47.             } catch (MessagingException e) {
  48.                 e.printStackTrace();
  49.             } 
  50.         };
  51.         new Thread(thread).start();
  53.     }

下面是递归方法：

  1. @Transactional
  2. private void dumpFolder(javax.mail.Folder jmailFolder, Folder folder, Account account) {
  3.     try {
  4.         if ((jmailFolder.getType() & javax.mail.Folder.HOLDS_FOLDERS) != 0) {
  6.                 Arrays.stream(jmailFolder.list()).forEach(f -> {
  7.                     Folder childFolder = null;
  9.                     try {
  10.                         childFolder = Folder.builder()
  11.                                         .fullFolderName(jmailFolder.getFullName())
  12.                                         .folderName(jmailFolder.getName())
  13.                                         .folderUrl(jmailFolder.getURLName().toString())
  14.                                         .children(new HashSet<Folder>())
  15.                                         .messages(new HashSet<Message>())
  16.                                         .parent(folder)
  17.                                         .account(account)
  18.                                         .build();
  19.                         } catch (MessagingException e) {
  21.                                 e.printStackTrace();
  22.                         }
  24.                     folderService.save(childFolder);
  25.                     dumpFolder(f, childFolder, account);
  27.                 });
  28.         }
  29.     } catch (MessagingException e) {
  30.         e.printStackTrace();
  31.     }
  33. }

有趣的是，可能有人会对如何以不同的方式执行递归有一个想法，那就是 list("%") 调用的方法 root :

在设置new runnable并启动new thread之前，我设法获取整个层次结构，但是对于new thread，我得到以下异常：

  1. Exception in thread "Thread-19" org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: com.uns.ac.rs.emailclient.model.Folder; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: com.uns.ac.rs.emailclient.model.Folder
  2.     at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:297)
  3.     at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:233)
  4.     at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:551)
  5.     at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61)
  6.     at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:242)
  7.     at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:152)
  8.     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  9.     at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:174)
  10.     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  11.     at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97)
  12.     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  13.     at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215)
  14.     at com.sun.proxy.$Proxy135.save(Unknown Source)
  15.     at com.uns.ac.rs.emailclient.service.impl.FolderServiceImpl.save(FolderServiceImpl.java:18)
  16.     at com.uns.ac.rs.emailclient.service.helper.JavaxMailHelper.lambda$2(JavaxMailHelper.java:101)
  17.     at java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
  18.     at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658)
  19.     at com.uns.ac.rs.emailclient.service.helper.JavaxMailHelper.dumpFolder(JavaxMailHelper.java:83)
  20.     at com.uns.ac.rs.emailclient.service.helper.JavaxMailHelper.lambda$1(JavaxMailHelper.java:61)
  21.     at java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
  22.     at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658)
  23.     at com.uns.ac.rs.emailclient.service.helper.JavaxMailHelper.lambda$0(JavaxMailHelper.java:47)
  24.     at java.base/java.lang.Thread.run(Thread.java:832)
  25. Caused by: org.hibernate.PersistentObjectException: detached entity passed to persist: com.uns.ac.rs.emailclient.model.Folder
  26.     at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:120)
  27.     at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:113)
  28.     at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:744)
  29.     at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:712)
  30.     at org.hibernate.engine.spi.CascadingActions$7.cascade(CascadingActions.java:298)
  31.     at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:492)
  32.     at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:416)
  33.     at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:218)
  34.     at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:151)
  35.     at org.hibernate.event.internal.AbstractSaveEventListener.cascadeBeforeSave(AbstractSaveEventListener.java:427)
  36.     at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:264)
  37.     at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:193)
  38.     at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:123)
  39.     at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:185)
  40.     at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:128)
  41.     at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:55)
  42.     at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102)
  43.     at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:720)
  44.     at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:706)
  45.     at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  46.     at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
  47.     at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  48.     at java.base/java.lang.reflect.Method.invoke(Method.java:564)
  49.     at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:311)
  50.     at com.sun.proxy.$Proxy132.persist(Unknown Source)
  51.     at org.springframework.data.jpa.repository.support.SimpleJpaRepository.save(SimpleJpaRepository.java:557)
  52.     at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  53.     at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
  54.     at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  55.     at java.base/java.lang.reflect.Method.invoke(Method.java:564)
  56.     at org.springframework.data.repository.core.support.RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0(RepositoryMethodInvoker.java:289)
  57.     at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:137)
  58.     at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:121)
  59.     at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:524)
  60.     at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:285)
  61.     at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:531)
  62.     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  63.     at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:156)
  64.     at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:131)
  65.     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  66.     at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:80)
  67.     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  68.     at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123)
  69.     at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388)
  70.     at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119)
  71.     at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  72.     at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137)
  73.     ... 17 more

所以问题是如何从一个单独的线程启动递归函数而不让hibernate发疯（通俗地说）？我不太精通hibernate和并发，所以任何帮助都是非常受欢迎的。抱歉，我的帖子太长了。

springspring-bootconcurrencyjakarta-mailrecursion

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