Hi, I can not create entity group because both are both classes can exists independently, It can be unowned relation between them. I want both should be stored in datastore or none of these(Atomic behavior ) . If one entity is not stored other entity must not store in datastore .
Didier's suggestion looks good , but i did not try . * * On Thu, Dec 16, 2010 at 8:35 PM, WillSpecht <willspe...@gmail.com> wrote: > Why do you want to store both in the same transaction? To me, it seems > transactions are used to guarantee two things happen. eg. you don't > want to delete one record without making sure the a log of deleted > records is updated. Transactions are also used to prevent collisions, > eg. I don't want two users adding to a counter at the same time and > one of their adds is lost. > > It seems neither of these is likely. It is unlikely that a new Person > will be created and before the system can save their mobile, some > other user will try and edit it. It is also unlikely that either of > these will fail and not fail gracefully. If you try and add a user in > one transaction then try to add a mobile in a second transaction > either both will succeed or fail. Same outcome as a single > transaction. Or one of the two fails and you simply try it again or > delete the one that didn't fail and inform the user. > > If you really need a single transaction you can put both items in the > same entity group using a key builder. > > You can see an example here under Creating Entities With Entity Groups > http://code.google.com/appengine/docs/java/datastore/transactions.html > > Dec 15, 10:16 pm, Didier Durand <durand.did...@gmail.com> wrote: > > Hi, > > > > If they don't belong to the same entity group, you will raise an > > exception by trying to store 2 objects in a single transaction. > > > > 2 ways to handle that: > > > > a) you make Mobile belong to same entity group as Person so you'll > > be able to store both in a single transaction. I understand in your > > question that you can't go this way. > > b) you store one let's say Person in first transaction and during > > this transaction, you start a task as part of the transaction: "You > > can enqueue a task as part of a datastore transaction, such that the > > task is only enqueued—and guaranteed to be enqueued—if the transaction > > is committed successfully. Tasks added within a transaction are > > considered to be a part of it and have the same level of isolation and > > consistency." as said inhttp:// > code.google.com/appengine/docs/java/taskqueue/overview.html#Ta... > > > > Hope it helps > > > > didier > > > > On Dec 15, 8:26 am, kartik kudada <kartik.kud...@gmail.com> wrote: > > > > > Can we store two unowned objects(one to many) in datastore in a single > > > transaction. > > > For example - We have > > > > > public class Person { > > > @PrimaryKey > > > @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) > > > private Long id; > > > > > @Persistent > > > private String name; > > > > > @Persistent > > > private List<Key> mobileIds = new ArrayList<Key>(); > > > > > //.... > > > //..... > > > } > > > > > public class Mobile { > > > > > @PrimaryKey > > > @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) > > > private Key mobileId; > > > > > // ... > > > //.... > > > > > } > > > > > I want to store these two objects in datastore in single transaction so > that > > > relation can be made in between both objects. > > > Tell me if any other solution is there ? > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine for Java" group. > To post to this group, send email to > google-appengine-j...@googlegroups.com. > To unsubscribe from this group, send email to > google-appengine-java+unsubscr...@googlegroups.com<google-appengine-java%2bunsubscr...@googlegroups.com> > . > For more options, visit this group at > http://groups.google.com/group/google-appengine-java?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-j...@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
