org.springframework.integration.channel.AbstractSubscribableChannel.java Source code

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Here is the source code for org.springframework.integration.channel.AbstractSubscribableChannel.java

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/*
 * Copyright 2002-2019 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.integration.channel;

import org.springframework.integration.MessageDispatchingException;
import org.springframework.integration.dispatcher.MessageDispatcher;
import org.springframework.integration.support.management.SubscribableChannelManagement;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageDeliveryException;
import org.springframework.messaging.MessageHandler;
import org.springframework.messaging.SubscribableChannel;
import org.springframework.util.Assert;

/**
 * Base implementation of {@link org.springframework.messaging.MessageChannel} that
 * invokes the subscribed {@link MessageHandler handler(s)} by delegating to a
 * {@link MessageDispatcher}.
 *
 * @author Mark Fisher
 * @author Oleg Zhurakousky
 * @author Gary Russell
 */
public abstract class AbstractSubscribableChannel extends AbstractMessageChannel
        implements SubscribableChannel, SubscribableChannelManagement {

    @Override
    public int getSubscriberCount() {
        return getRequiredDispatcher().getHandlerCount();
    }

    @Override
    public boolean subscribe(MessageHandler handler) {
        MessageDispatcher dispatcher = getRequiredDispatcher();
        boolean added = dispatcher.addHandler(handler);
        adjustCounterIfNecessary(dispatcher, added ? 1 : 0);
        return added;
    }

    @Override
    public boolean unsubscribe(MessageHandler handle) {
        MessageDispatcher dispatcher = getRequiredDispatcher();
        boolean removed = dispatcher.removeHandler(handle);
        this.adjustCounterIfNecessary(dispatcher, removed ? -1 : 0);
        return removed;
    }

    private void adjustCounterIfNecessary(MessageDispatcher dispatcher, int delta) {
        if (delta != 0) {
            if (logger.isInfoEnabled()) {
                logger.info("Channel '" + this.getFullChannelName() + "' has " + dispatcher.getHandlerCount()
                        + " subscriber(s).");
            }
        }
    }

    @Override
    protected boolean doSend(Message<?> message, long timeout) {
        try {
            return getRequiredDispatcher().dispatch(message);
        } catch (MessageDispatchingException e) {
            String description = e.getMessage() + " for channel '" + this.getFullChannelName() + "'.";
            throw new MessageDeliveryException(message, description, e);
        }
    }

    private MessageDispatcher getRequiredDispatcher() {
        MessageDispatcher dispatcher = getDispatcher();
        Assert.state(dispatcher != null, "'dispatcher' must not be null");
        return dispatcher;
    }

    protected abstract MessageDispatcher getDispatcher();

}