JPA 2.2 `EntityManager.merge` 插入而不是更新

如何解决JPA 2.2 `EntityManager.merge` 插入而不是更新

我只有这个简单的实体（根本没有关系，只有一些标量字段）：

@Entity
@Table
@Access(AccessType.FIELD)
public class MyEntity {

  @Id
  @Column
  private String myPK;

  /* ...other fields... */

  public MyEntity(String myPK /* ... other fields ... */) {
    this.myPK = myPK;
    /* ... */
  }

  /* getters and setters and toString and hashcode et al. */
}

然后在测试运行开始时我执行此操作（在 arquillian 中，但这并不重要）：

EntityManager manager;
/* ... manager is injected actually ... */
manager.merge(new MyEntity("0" /* ... */));

它有效。也就是说，PK 为 "0" 的表行更新了剩余字段，因此测试具有稳定的起点。

现在我已将 myPK 字段更改为 Long 而不是 String。是的，仅此更改（以及 new MyEntity(0L /* ... */)）。

它不再起作用了。

merge 实际上试图插入一个新行，而前一行已经存在。然后数据库拒绝插入重复的PK。

为什么在使用 String 作为 PK 时它更新行，但在使用 Long 作为 PK 时它插入？

我使用的是 OpenLiberty 21.0.0.4 (wlp-1.0.51.cl210420210407-0944)。

它使用 EclipseLink，版本：Eclipse Persistence Services - 2.7.8.v20201217-ecdf3c32c4。

在事务提交时溢出：

 Caused by: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.7.8.v20201217-ecdf3c32c4): org.eclipse.persistence.exceptions.DatabaseException
 Internal Exception: java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (XPK) violate

 Error Code: 1
 Call: INSERT INTO MyEntity (myPK,...) VALUES (?,...)
     bind => [0,...]
 Query: InsertObjectQuery(MyEntity(myPK=0,...))
     at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:333)
     at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeDirectNoSelect(DatabaseAccessor.java:908)
     at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeNoSelect(DatabaseAccessor.java:970)
     at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:640)
     at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:567)
     at org.eclipse.persistence.internal.sessions.AbstractSession.basicExecuteCall(AbstractSession.java:2099)
     at org.eclipse.persistence.sessions.server.ClientSession.executeCall(ClientSession.java:313)
     at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:277)
     at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.executeCall(DatasourceCallQueryMechanism.java:263)
     at org.eclipse.persistence.internal.queries.DatasourceCallQueryMechanism.insertObject(DatasourceCallQueryMechanism.java:413)
     at org.eclipse.persistence.internal.queries.StatementQueryMechanism.insertObject(StatementQueryMechanism.java:167)
     at org.eclipse.persistence.internal.queries.StatementQueryMechanism.insertObject(StatementQueryMechanism.java:182)
     at org.eclipse.persistence.internal.queries.DatabaseQueryMechanism.insertObjectForWrite(DatabaseQueryMechanism.java:504)
     at org.eclipse.persistence.queries.InsertObjectQuery.executeCommit(InsertObjectQuery.java:82)
     at org.eclipse.persistence.queries.InsertObjectQuery.executeCommitWithChangeSet(InsertObjectQuery.java:92)
     at org.eclipse.persistence.internal.queries.DatabaseQueryMechanism.executeWriteWithChangeSet(DatabaseQueryMechanism.java:316)
     at org.eclipse.persistence.queries.WriteObjectQuery.executeDatabaseQuery(WriteObjectQuery.java:60)
     at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:911)
     at org.eclipse.persistence.queries.DatabaseQuery.executeInUnitOfWork(DatabaseQuery.java:810)
     at org.eclipse.persistence.queries.ObjectLevelModifyQuery.executeInUnitOfWorkObjectLevelModifyQuery(ObjectLevelModifyQuery.java:110)
     at org.eclipse.persistence.queries.ObjectLevelModifyQuery.executeInUnitOfWork(ObjectLevelModifyQuery.java:87)
     at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2983)
     at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1898)
     at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1880)
     at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1830)
     at org.eclipse.persistence.internal.sessions.CommitManager.commitNewObjectsForClassWithChangeSet(CommitManager.java:229)
     at org.eclipse.persistence.internal.sessions.CommitManager.commitAllObjectsForClassWithChangeSet(CommitManager.java:196)
     at org.eclipse.persistence.internal.sessions.CommitManager.commitAllObjectsWithChangeSet(CommitManager.java:141)
     at org.eclipse.persistence.internal.sessions.AbstractSession.writeAllObjectsWithChangeSet(AbstractSession.java:4398)