I've seen the link for previous version Java API corresponding to update_by_query but I didn't see some reference for 5.0.0-AlphaX. There is some information about how to use it from Java API or the best way is to call Vanilla Rest API?
For now you might be stuck with REST. We haven't published the jars for any of the modules for 5.0 by mistake. I believe that has been fixed in master as of a couple of days ago. So for the next alpha/beta/whatever-it-is there will be a transport client jar with all the right dependencies. You shouldn't need to do the maven steps or the
Although the alpha says that it isn't intended for production I'm using in a product that is in Beta on a customer, so I'll start with Rest and change for Java API on next release.
Just remember that the alphas aren't wire or on disk compatible with each other. So you'll need a full cluster restart when you upgrade and the index might not work. So you might have to delete it and reindex.
It won't be a problem. I'm prepared to do that actions and my customer too