AbstractClientFactory.java

package com.ustcinfo.rpc.client;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.FutureTask;

public abstract class AbstractClientFactory implements ClientFactory {

	// Cache client
	private static ConcurrentHashMap<String, FutureTask<List<Client>>> clients = 
		new ConcurrentHashMap<String, FutureTask<List<Client>>>();
	
	public Client get(final String targetIP, final int targetPort,
			final int connectTimeout) throws Exception {
		return get(targetIP, targetPort, connectTimeout, 1);
	}

	public Client get(final String targetIP, final int targetPort,
			final int connectTimeout, final int clientNums)
			throws Exception {
		String key = targetIP + ":" + targetPort;

		if (clients.containsKey(key)) {
			if (clientNums == 1) {
				return clients.get(key).get().get(0);
			} else {
				Random random = new Random();
				return clients.get(key).get().get(random.nextInt(clientNums));
			}
		}
		else {
			final String cacheKey = key;
			FutureTask<List<Client>> task = new FutureTask<List<Client>>(
					new Callable<List<Client>>() {
						public List<Client> call() throws Exception {
							List<Client> clients = new ArrayList<Client>(
									clientNums);
							for (int i = 0; i < clientNums; i++) {
								clients.add(createClient(targetIP, targetPort,
										connectTimeout, cacheKey));
							}
							return clients;
						}
					});
			FutureTask<List<Client>> currentTask = clients.putIfAbsent(key,task);
			if (currentTask == null) {
				task.run();
			} 
			else {
				task = currentTask;
			}
			if (clientNums == 1)
				return task.get().get(0);
			else {
				Random random = new Random();
				return task.get().get(random.nextInt(clientNums));
			}
		}
	}

	public void removeClient(String key) {
		try {
			clients.remove(key);
		} catch (Exception e) {
			// IGNORE
		}
	}

	public static ClientFactory getInstance() {
		throw new UnsupportedOperationException(
				"should be implemented by true class");
	}

	protected abstract Client createClient(String targetIP, int targetPort,
			int connectTimeout, String key) throws Exception;

}