SQSUtils.java

//
// typica - A client library for Amazon Web Services
// Copyright (C) 2007 Xerox Corporation
// 
// 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.xerox.amazonws.sqs2;

import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * This class provides helper methods to interact with the Amazon Simple Queue Service.
 *
 * @author D. Kavanagh
 * @author developer@dotech.com
 */
public class SQSUtils {
    private static Log logger = LogFactory.getLog(SQSUtils.class);
    
	/**
	 * Returns a message queue for a given name, credentials. Uses the default SQS host.
	 *
	 * @param queueName name of the queue to connect to
	 * @param accessKey AWS access id
	 * @param secretKey AWS secret key
	 * @return object representing the message queue
	 */
	public static MessageQueue connectToQueue(String queueName, String accessKey, String secretKey) 
			throws SQSException {
		return connectToQueue(null, queueName, accessKey, secretKey);
	}

	/**
	 * Returns a message queue for a given name, credentials.
	 *
	 * @param serverName name of the host to use
	 * @param queueName name of the queue to connect to
	 * @param accessKey AWS access id
	 * @param secretKey AWS secret key
	 * @return object representing the message queue
	 */
	public static MessageQueue connectToQueue(String serverName, String queueName,
                                              String accessKey, String secretKey) 
			throws SQSException {
		// Create the service object
		QueueService service = getQueueService(accessKey, secretKey, serverName);
		 
		// Retrieve the message queue object (by name).
		return getMessageQueue(service, queueName);
	}

	/**
	 * Create a QueueService object for a given URL.
	 *
	 * @param accessKey AWS access id
	 * @param secretKey AWS secret key
	 * @param serverName name of the host to use
	 * @return object representing the queue service
	 */
	public static QueueService getQueueService(String accessKey, String secretKey, String serverName) 
			throws SQSException {
		QueueService service = null;
		if (serverName != null) {
			service = new QueueService(accessKey, secretKey, true, serverName);
		}
		else {
			service = new QueueService(accessKey, secretKey);
		}
		if (service.getUrl() != null) {
			logger.debug( "Service: " + service.getUrl().toString() );
		} else {
			logger.error( "Service: null url!" );
		}
		return service;
	}
	
	
	/**
	 * Looks for a queue by name: if found, return a MessageQuueue object for it.
	 * Else, return null.
	 *
	 * @deprecated This method was for compatibility with the old AWS SQS client
	 *             (@see getQueueOrElse)
	 * @param service the queue service we're using
	 * @param msgQueueName the name of the message queue to find, or create
	 * @return object representing the message queue
	 */
	public static MessageQueue getMessageQueue(QueueService service, String msgQueueName)
			throws SQSException {
		MessageQueue msgQueue = null;
		MessageQueue msgQueueFound = null;
		List<MessageQueue> msgQueuesFound = service.listMessageQueues( null );
		for ( MessageQueue mq : msgQueuesFound ) {
			if ( mq.getUrl().toString().endsWith( msgQueueName ) ) {
				msgQueueFound = mq;
			}
		}
		if (msgQueueFound == null) {
			logger.debug("Message queue couldn't be listed, going to create it.");
			msgQueue = service.getOrCreateMessageQueue(msgQueueName.substring(msgQueueName.lastIndexOf("/")+1));
		} else if (msgQueue == null) {
			msgQueue = msgQueueFound;
		}
		if (msgQueue == null) {
			logger.error( "Couldn't find message queue " + msgQueueName);
		} else {
			logger.debug( "Using message queue resource at " + msgQueue.getUrl() ); 
		}
		return msgQueue;
	}

	/**
	 * This method will block until the requested message queue is fetched or created.
	 * Good for those times when the app simply must have a message queue to run.
	 *
	 * @param qs the queue service we're using
	 * @param queueName the name of the queue to find or create
	 * @return object representing the message queue
	 */
	public static MessageQueue getQueueOrElse(QueueService qs, String queueName) {
		MessageQueue ret = null;
		while (ret == null) {
			try {
				ret = qs.getOrCreateMessageQueue(queueName);
			} catch (SQSException ex) {
				logger.error("Error access message queue, Retrying.", ex);
				try { Thread.sleep(1000); } catch (InterruptedException iex) { }
			}
		}
		return ret;
	}

	/**
	 * This method will block until the message has been sent.
	 * Good for those times when the app simply must send the message to proceed.
	 *
	 * @param queue the queue the message is sent to
	 * @param message the message to send
	 */
	public static void sendMessageForSure(MessageQueue queue, String message) {
		while (true) {
			try {
				queue.sendMessage(message);
				return;
			} catch (SQSException ex) {
				logger.warn("Error sending message, Retrying.");
				try { Thread.sleep(2000); } catch (InterruptedException iex) {}
			}
		}
	}
}