TransportFactory.java

package backtype.storm.messaging;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Map;

import org.apache.log4j.Logger;

import backtype.storm.Config;

public class TransportFactory {
	public static final Logger LOG = Logger.getLogger(TransportFactory.class);

	public static IContext makeContext(Map storm_conf) {

		// get factory class name
		String transport_plugin_klassName = (String) storm_conf
				.get(Config.STORM_MESSAGING_TRANSPORT);
		LOG.info("JStorm peer transport plugin:" + transport_plugin_klassName);

		IContext transport = null;
		try {
			// create a factory class
			Class klass = Class.forName(transport_plugin_klassName);
			// obtain a context object
			// Object obj = klass.newInstance();
			Constructor constructor = klass.getDeclaredConstructor();
			constructor.setAccessible(true);
			Object obj = constructor.newInstance();
			LOG.info("TransportFactory makeContext: new klass: " + obj);
			if (obj instanceof IContext) {
				// case 1: plugin is a IContext class
				transport = (IContext) obj;
				// initialize with storm configuration
				transport.prepare(storm_conf);
				LOG.info("TransportFactory makeContext: start prepare... "
						+ storm_conf);
			} else {
				// case 2: Non-IContext plugin must have a
				// makeContext(storm_conf) method that returns IContext object
				Method method = klass.getMethod("makeContext", Map.class);
				LOG.debug("object:" + obj + " method:" + method);
				transport = (IContext) method.invoke(obj, storm_conf);
			}
			LOG.info("TransportFactory makeContext done...");
		} catch (Exception e) {
			throw new RuntimeException(
					"Fail to construct messaging plugin from plugin "
							+ transport_plugin_klassName, e);
		}
		return transport;
	}

}