router.java

华为编程开发规范与案例, 华为编程开发规范与案例,华为编程开发规范与案例

// SMSLib for Java v3
// A Java API library for sending and receiving SMS via a GSM modem
// or other supported gateways.
// Web Site: http://www.smslib.org
//
// SMSLib is distributed under the terms of the Apache License version 2.0
//
// Copyright (C) 2002-2007, Thanasis Delenikas, Athens/GREECE
// Portions Copyright:
// Davide Bettoni, Clusone/ITALY, [e-mail]
// Tomek Cejner, Polland, [e-mail]
//
// 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 org.smslib.routing;

import java.util.ArrayList;

import org.smslib.OutboundMessage;
import org.smslib.Service;
import org.smslib.gateway.AbstractGateway;
import org.smslib.gateway.AbstractGateway.Attributes;


/**
 * Base message routing class. Service owns instance of Router (or its
 * subclass), and uses its memeber functions to designate gateway(s) to send
 * particular outgoing message.
 * 
 * It is allowed that router designates more than modem to send message. It is
 * responsibility of Router to decide which gateway will send the message.
 * 
 * Custom routing rules are posiible by creating subclass.
 * 
 * @author heretique
 */
public class Router
{

	/** List of candidate gateways */
	protected ArrayList<AbstractGateway> candidates;
	
	/** List of gateways that are allowed to send message */ 
	protected ArrayList<AbstractGateway> allowed;

	protected Service service;

	public Router()
	{
		candidates = new ArrayList<AbstractGateway>();
		allowed = new ArrayList<AbstractGateway>();
	}

	/**
	 * Perform early-stage routing, pick gateways that meet minimal
	 * requirements to send message (for example are set to handle
	 * outbound messages).
	 * 
	 * @param msg
	 *           Message to be routed
	 */
	protected void preroute(OutboundMessage msg)
	{
		for (AbstractGateway gw : service.getGatewayList())
		{
			// TODO should we skip gateway if it lacks features that are not critical? 
			if (gw.isOutbound() && gw.conformsTo(Attributes.BIGMESSAGES, msg.isBig()) )
			{
				candidates.add(gw);
			}
		}
	}

	/**
	 * Heart of routing & loadbalancing mechanism
	 * @param msg
	 * @throws Exception
	 */
	public void route(OutboundMessage msg) throws Exception
	{
		beginRouting();
		preroute(msg);
		// perform custom routing
		customRouting(msg);
		// chain to loadbalancer
		service.getLoadBalancer().sendMessage(msg, allowed);
		// finish
		finishRouting();
	}
	
	
	/**
	 * Place for custom routing performed by specialized subclass.
	 *
	 * A "positive" approach is taken. Method has to copy references
	 * to gateways from <code>candidates</code> list to <code>allowed</code>. 
	 * So, default behavior is to copy all references. 
	 * 
	 * Another possibility is to take "negative" approach, where
	 * method should delete unwanted gateways from list. This approach was
	 * found difficult to use at this time.
	 * 
	 * @param msg
	 */
	protected void customRouting(OutboundMessage msg)
	{
		allowed.addAll(candidates);
	}
	
	
	/**
	 * Prepare internal data for routing (clean internal data structures). 
	 * Must be called when new message is routed.
	 * 
	 */
	protected final void beginRouting()
	{
		candidates.clear();
		allowed.clear();
	}

	protected final void finishRouting()
	{
		candidates.clear();
		allowed.clear();
	}
	
	public Service getService()
	{
		return service;
	}

	public void setService(Service service)
	{
		this.service = service;
	}

	
}