如果上述解决方案不工作，只需一次注释实体类的getter和setter方法，并且不设置id的值。(主键) 这样就可以了。

您需要为每个帐户设置事务。

foreach(Account account : accounts){
    account.setTransaction(transactionObj);
}

或者在许多方面将id设置为null就足够了(如果合适的话)。

// list of existing accounts
List<Account> accounts = new ArrayList<>(transactionObj.getAccounts());

foreach(Account account : accounts){
    account.setId(null);
}

transactionObj.setAccounts(accounts);

// just persist transactionObj using EntityManager merge() method.

使用合并是有风险和棘手的，所以在您的情况下，这是一种肮脏的变通方法。您至少需要记住，当您将一个实体对象传递给merge时，它将停止附加到事务，而是返回一个新的、现在已附加的实体。这意味着如果任何人仍然拥有旧的实体对象，那么对它的更改将被无声地忽略并在提交时丢弃。

You are not showing the complete code here, so I cannot double-check your transaction pattern. One way to get to a situation like this is if you don't have a transaction active when executing the merge and persist. In that case persistence provider is expected to open a new transaction for every JPA operation you perform and immediately commit and close it before the call returns. If this is the case, the merge would be run in a first transaction and then after the merge method returns, the transaction is completed and closed and the returned entity is now detached. The persist below it would then open a second transaction, and trying to refer to an entity that is detached, giving an exception. Always wrap your code inside a transaction unless you know very well what you are doing.

使用容器管理的事务，它看起来像这样。注意:这假设方法在会话bean中，并通过本地或远程接口调用。

@TransactionAttribute(TransactionAttributeType.REQUIRED)
public void storeAccount(Account account) {
    ...

    if (account.getId()!=null) {
        account = entityManager.merge(account);
    }

    Transaction transaction = new Transaction(account,"other stuff");

    entityManager.persist(account);
}

移除子关联级联

因此，您需要删除@CascadeType。这些都来自@ManyToOne协会。子实体不应该级联到父关联。只有父实体应该级联到子实体。

@ManyToOne(fetch= FetchType.LAZY)

注意，我将fetch属性设置为FetchType。LAZY，因为急切抓取对性能非常不利。

设置关联的双方

当你有一个双向关联时，你需要在父实体中使用addChild和removecchild方法来同步双方:

public void addTransaction(Transaction transaction) {
    transcations.add(transaction);
    transaction.setAccount(this);
}

public void removeTransaction(Transaction transaction) {
    transcations.remove(transaction);
    transaction.setAccount(null);
}

解决方案很简单，只需使用CascadeType。MERGE而不是CascadeType。PERSIST或CascadeType.ALL。

我也遇到过同样的问题和CascadeType。MERGE对我很有效。

我希望你已经整理好了。

在我的情况下，我正在提交事务时，持久化方法被使用。 在更改persist to save方法时，该问题得到了解决。