问题
I use JPA within GAE to persist objects.
javax.persistence.PersistenceException: Illegal argument
at org.datanucleus.api.jpa.NucleusJPAHelper.getJPAExceptionForNucleusException(NucleusJPAHelper.java:298)
at org.datanucleus.api.jpa.JPAEntityTransaction.commit(JPAEntityTransaction.java:122)
Caused by: java.lang.IllegalArgumentException: cross-group transaction need to be explicitly specified, see TransactionOptions.Builder.withXGfound both
Element {
type: "Event"
id: 0x11000000000000
}
and Element {
type: "User"
id: 0x14000000000000
}
There is a bidirectional Many-To-Many relationship between Event and User. When I insert a new Event and bound it to existing Users inside a transaction, I get the above exception.
From the error message I see that I need to tweak TransactionOptions. Where can I set these options?
回答1:
Set the following property in persistence.xml:
<property name="datanucleus.appengine.datastoreEnableXGTransactions" value="true" />
There is currently no way to enable XG transactions for an individual JDO or JPA transaction. Instead, you specify this for all transactions. [docs]
来源：https://stackoverflow.com/questions/29606651/where-do-i-set-transactionoptions-with-jpa-google-app-engine