mangotiger.util.EventBus.java Source code

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Here is the source code for mangotiger.util.EventBus.java

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/*
 * $Source: $
 *
 * Copyright (C) 2002-2005, Thomas Robert Gagnier, Jr., All Rights Reserved.
 * Unauthorized use, disclosure or reproduction of this source code is strictly
 * prohibited by United States copyright law and international treaty provisions.
 * Use of source code requires an appropriate source license.
 */
package mangotiger.util;

import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

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

/** @author Tom Gagnier */
public class EventBus {
    private final Map<Class, List<Object>> consumersByEvent = new HashMap<Class, List<Object>>();
    private final Map<Class, HashMap<Class, Method>> methodsByConsumerByEvent = new HashMap<Class, HashMap<Class, Method>>();
    private final String method;

    public EventBus() {
        this("handle");
    }

    public EventBus(final String method) {
        this.method = method;
    }

    public void register(final Class event, final Object consumer) {
        registerMethod(event, consumer.getClass());
        registerConsumer(event, consumer);
    }

    private void registerMethod(final Class event, final Class consumer) {
        try {
            methodsByConsumer(event).put(consumer, consumer.getMethod(method, event));
        } catch (NoSuchMethodException e) {
            throw new IllegalArgumentException(e);
        }
    }

    private Map<Class, Method> methodsByConsumer(final Class event) {
        if (!methodsByConsumerByEvent.containsKey(event)) {
            methodsByConsumerByEvent.put(event, new HashMap<Class, Method>());
        }
        return methodsByConsumerByEvent.get(event);
    }

    private void registerConsumer(final Class event, final Object consumer) {
        if (!consumersByEvent.containsKey(event)) {
            consumersByEvent.put(event, new LinkedList<Object>());
        }
        consumersByEvent.get(event).add(consumer);
    }

    public void publish(final Object event) {
        if (event == null)
            return;
        if (!consumersByEvent.containsKey(event.getClass()))
            return;
        for (Iterator<Object> iterator = consumersByEvent.get(event.getClass()).iterator(); iterator.hasNext();) {
            final Object consumer = iterator.next();
            try {
                methodsByConsumerByEvent.get(event.getClass()).get(consumer.getClass()).invoke(consumer, event);
            } catch (Exception e) {
                log().error(new StringBuilder().append("unable to publish due to ").append(e)
                        .append(", removing consumer: ").append(consumer).append("), unable to handle bus: ")
                        .append(event));
                iterator.remove();
            }
        }
    }

    private static Log log() {
        return LogFactory.getLog(EventBus.class);
    }
}