检测事务是否失败并通过objectify重新运行

Question

I am using objectify as an interface to the GAE datastore and am wondering how I can detect when a transaction fails. That is, when you call

ofy().transact(new VoidWork() {
    public void vrun() {
    //save entity, this may throw - concurrent modification exception 
    }
});

If an exception is thrown, the vrun() method is called again. I would like to log when this happens. I have tried many things - surrounding the contents of vrun() with a try/catch, passing a reference to a boolean flag, etc. But this does not appear to work. Any ideas where I might be going wrong?

I need to be able to programmatically detect if the transaction failed , and have some code execute before it is reattempted.

Answer 1

Use the overload for transactNew() that limits the # of tries:

ofy().transactNew(1, new VoidWork() {
    ...
});

This will let you manage retries on your own. Note that prior to v5.1.6, the # was erroneously being used as a # of retries (not tries). In v5.1.6, behavior was corrected to match the documentation. It's the # of tries.