我遇到了同样的问题，因为我创建了一个新的object：

I had the same problem, because I created a new object:

DatabaseObject obj = new DatabaseObject();
obj.setSomeValue(null);
obj.setRowId(1);
entityManager.merge(obj);

我想如果我明确设置了id号，那么如果JPA对象是新的则无关紧要，或具有所需id的现有。也许你做了同样的事情？

I thought if I explicitly set the id number that it wouldn't matter if the JPA object is new, or the existing one with the desired id. Perhaps you did the same?

正确的代码是：

DatabaseObject obj = entityManager.find(DatabaseObject.class, (long) 1);
obj.setSomeValue(null);
obj.setRowId(1);
entityManager.merge(obj);

我希望这有帮助。