Is static init repeated for each request?

Question

I've been assuming that static initialization (e.g. for my persistence library) will persist between requests for a given instance? Suddenly it occurred to me that maybe I'm wrong - maybe my app's init is redone for each request even on a warm instance.

Here's why I'm asking:

I have a request handler (it happens to be a Google Endpoint, but I don't think that is relevant) that receives a list of entities and saves them.

The entities can be any of 20 different types, so my static initialization 'registers' all 20 different entity types. I happen to be using objectify, so it looks like this:

@Api(name = "myendpoint")
public class MyEndpoint {
  static {
    ObjectifyService.register( EntityOne.class );
    ObjectifyService.register( EntityTwo.class );
    ... x20
  }

If it is doing all this 'registering' for each request then I had better change this to only register for the entities needed for the request.

(On the other hand, if I'm right and my static init is only done when creating a new instance then I should put as much initialization as I can into the static init.)

Answer 1

Static initializer blocks are run once when the class is being loaded.

Answer 2

Yes, static initialization blocks are only run when the class is being loaded. That means that it happens only once per GAE instance.

Something else worth considering: It is often better to register these classes with Ofy via your own Objectify service class, and then use that to access Objectify functionality. See https://code.google.com/p/objectify-appengine/wiki/BestPractices ... That ensures that the blocks are run before any datastore access happens.