PersistentObjectException: detached entity passed to persist thrown by JPA and Hibernate

Question

I have a JPA-persisted object model that contains a many-to-one relationship: an Account has many Transactions. A Transaction has one

Answer 1

You need to set Transaction for every Account.

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

Or it colud be enough (if appropriate) to set ids to null on many side.

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

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

transactionObj.setAccounts(accounts);

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