com.google.web.bindery.requestfactory.gwt.client.RequestBatcher Maven / Gradle / Ivy
/*
* Copyright 2011 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.web.bindery.requestfactory.gwt.client;
import com.google.gwt.core.client.Scheduler;
import com.google.gwt.core.client.Scheduler.ScheduledCommand;
import com.google.web.bindery.requestfactory.shared.Receiver;
import com.google.web.bindery.requestfactory.shared.RequestContext;
import com.google.web.bindery.requestfactory.shared.RequestFactory;
import com.google.web.bindery.requestfactory.shared.impl.AbstractRequestContext;
/**
* A RequestBatcher is a convenience class that allows RequestFactory operations
* to be aggregated over a single tick of the event loop and sent as one HTTP
* request. Instances of RequestBatcher are reusable, so they may be used as
* application-wide singleton objects or within a particular subsystem or UI.
*
* Subclasses need only to provide the instance of the RequestFactory used by
* the application and a method to provide a "default" RequestContext from the
* RequestFactory.
*
*
* public class MyRequestBatcher extends RequestBatcher {
* public MyRequestBatcher() {
* // MyRequestFactory could also be injected
* super(GWT.create(MyRequestFactory.class));
* }
*
* protected MyRequestContext createContext(MyRequestFactory factory) {
* return factory.myRequestContext();
* }
* }
*
* A singleton or otherwise scoped instance of RequestBatcher should be injected
* into consuming classes. The {@link RequestContext#fire()} and
* {@link com.google.web.bindery.requestfactory.shared.Request#fire()
* Request.fire()} methods reachable from the RequestContext returned from
* {@link #get()} will not trigger an HTTP request. The
* {@link RequestContext#fire(Receiver)} and
* {@link com.google.web.bindery.requestfactory.shared.Request#fire(Receiver)
* Request.fire(Receiver)} methods will register their associated Receivers as
* usual. This allows consuming code to be written that can be used with or
* without a RequestBatcher.
*
* When an application uses multiple RequestContext types, the
* {@link RequestContext#append(RequestContext)} method can be used to chain
* multiple RequestContext objects together:
*
*
* class MyRequestBatcher {
* public OtherRequestContext otherContext() {
* return get().append(getFactory().otherContext());
* }
* }
*
*
* @param the type of RequestFactory
* @param any RequestContext type
* @see Scheduler#scheduleFinally(ScheduledCommand)
*/
public abstract class RequestBatcher {
private C openContext;
private AbstractRequestContext openContextImpl;
private final F requestFactory;
protected RequestBatcher(F requestFactory) {
this.requestFactory = requestFactory;
}
/**
* Returns a mutable {@link RequestContext}.
*/
public C get() {
return get(null);
}
/**
* Returns a mutable {@link RequestContext} and enqueues the given receiver to
* be called as though it had been passed directly to
* {@link RequestContext#fire(Receiver)}.
*/
public C get(Receiver receiver) {
if (openContext == null) {
openContext = createContext(requestFactory);
openContextImpl = (AbstractRequestContext) openContext;
openContextImpl.setFireDisabled(true);
getScheduler().scheduleFinally(new ScheduledCommand() {
@Override
public void execute() {
assert !openContextImpl.isLocked() : "AbstractRequestContext.fire() should have been a no-op";
openContextImpl.setFireDisabled(false);
openContext.fire();
openContext = null;
openContextImpl = null;
}
});
}
if (receiver != null) {
// Queue a final callback receiver
openContextImpl.fire(receiver);
}
return openContext;
}
/**
* Convenience access to the RequestFactory instance to aid developers using
* multiple RequestContext types.
*
*
* RequestBatcher{@literal } batcher;
*
* public void useOtherRequestContext() {
* OtherRequestContext ctx = batcher.get().append(batcher.getFactory().otherContext());
* ctx.someOtherMethod().to(someReceiver);
* }
*
*/
public F getRequestFactory() {
return requestFactory;
}
/**
* Subclasses must implement this method to return an instance of a
* RequestContext.
*/
protected abstract C createContext(F requestFactory);
/**
* Returns {@link Scheduler#get()}, but may be overridden for testing
* purposes.
*/
protected Scheduler getScheduler() {
return Scheduler.get();
}
}