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Asynchronous utilities for Java and GWT applications. Includes a simple promise implementation for Java.

There is a newer version: 0.1.5

/*******************************************************************************
 * Copyright 2011 Max Erik Rohde http://www.mxro.de
 * 
 * All rights reserved.
 ******************************************************************************/
package delight.async.flow;

import delight.async.Value;
import delight.async.callbacks.ListCallback;
import delight.async.callbacks.ValueCallback;
import delight.functional.collections.CollectionsUtils;
import delight.functional.collections.IdentityArrayList;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * This utility class supports in writing Java in a more asynchronous style.
 * This class allows to collect the results from various callbacks, which
 * result from calling a method on all elements of a list. The callback provided
 * by this class will only be called if all the callbacks for the individual
 * list elements have been executed.
 * 
 * @author Max Rohde
 * 
 * @param 
 * @param 
 */
public class CallbackMap {
	final Map responseMap;
	final List messages;
	final int expectedSize;
	final ListCallback callback;

	
	public ValueCallback createCallback(final GInput message) {
		return new ValueCallback() {

			@Override
			public void onSuccess(final GOutput response) {
				synchronized (responseMap) {
					responseMap.put(messages.indexOf(message), response);

					if (CollectionsUtils.isMapComplete(responseMap, expectedSize)) {
						final List localResponses = CollectionsUtils
								.toOrderedList(responseMap);

						callback.onSuccess(localResponses);
					}
				}
			}

			Value failureReported = new Value(false);

			@Override
			public void onFailure(final Throwable t) {
				// failure should be reported only once.
				synchronized (failureReported) {
					if (!failureReported.get()) {
						callback.onFailure(t);
					} else {
						throw new RuntimeException(t); // TODO maybe disable ...
					}
					failureReported.set(true);
				}
			}

		};
	}

	public CallbackMap(final List messages,
			final ListCallback callback) {
		super();
		this.messages = new IdentityArrayList(messages);
		this.responseMap = new HashMap();
		expectedSize = messages.size();
		this.callback = callback;

		if (expectedSize == 0) {
			this.callback.onSuccess(new ArrayList(0));
		}
	}

}