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

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Here is the source code for org.springframework.integration.channel.ExecutorChannel.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 java.util.concurrent.Executor;

import org.springframework.integration.context.IntegrationProperties;
import org.springframework.integration.dispatcher.LoadBalancingStrategy;
import org.springframework.integration.dispatcher.RoundRobinLoadBalancingStrategy;
import org.springframework.integration.dispatcher.UnicastingDispatcher;
import org.springframework.integration.util.ErrorHandlingTaskExecutor;
import org.springframework.util.Assert;
import org.springframework.util.ErrorHandler;

/**
 * An implementation of {@link org.springframework.messaging.MessageChannel}
 * that delegates to an instance of
 * {@link UnicastingDispatcher} which in turn delegates all dispatching
 * invocations to an {@link Executor}.
 * <p>
 * <em><b>NOTE</b>: unlike DirectChannel, the ExecutorChannel does not support a
 * shared transactional context between sender and handler, because the
 * {@link Executor} typically does not block the sender's Thread since it
 * uses another Thread for the dispatch.</em> (SyncTaskExecutor is an
 * exception but would provide no value for this channel. If synchronous
 * dispatching is required, a DirectChannel should be used instead).
 *
 * @author Mark Fisher
 * @author Gary Russell
 * @author Artem Bilan
 * @since 1.0.3
 */
public class ExecutorChannel extends AbstractExecutorChannel {

    private volatile boolean failover = true;

    private volatile LoadBalancingStrategy loadBalancingStrategy;

    /**
     * Create an ExecutorChannel that delegates to the provided
     * {@link Executor} when dispatching Messages.
     * <p>
     * The Executor must not be null.
     * @param executor The executor.
     */
    public ExecutorChannel(Executor executor) {
        this(executor, new RoundRobinLoadBalancingStrategy());
    }

    /**
     * Create an ExecutorChannel with a {@link LoadBalancingStrategy} that
     * delegates to the provided {@link Executor} when dispatching Messages.
     * <p>
     * The Executor must not be null.
     * @param executor The executor.
     * @param loadBalancingStrategy The load balancing strategy implementation.
     */
    public ExecutorChannel(Executor executor, LoadBalancingStrategy loadBalancingStrategy) {
        super(executor);
        Assert.notNull(executor, "executor must not be null");
        UnicastingDispatcher unicastingDispatcher = new UnicastingDispatcher(executor);
        if (loadBalancingStrategy != null) {
            this.loadBalancingStrategy = loadBalancingStrategy;
            unicastingDispatcher.setLoadBalancingStrategy(loadBalancingStrategy);
        }
        this.dispatcher = unicastingDispatcher;
    }

    /**
     * Specify whether the channel's dispatcher should have failover enabled.
     * By default, it will. Set this value to 'false' to disable it.
     * @param failover The failover boolean.
     */
    public void setFailover(boolean failover) {
        this.failover = failover;
        getDispatcher().setFailover(failover);
    }

    @Override
    protected UnicastingDispatcher getDispatcher() {
        return (UnicastingDispatcher) this.dispatcher;
    }

    @Override
    public final void onInit() {
        Assert.state(getDispatcher().getHandlerCount() == 0, "You cannot subscribe() until the channel "
                + "bean is fully initialized by the framework. Do not subscribe in a @Bean definition");
        super.onInit();
        if (!(this.executor instanceof ErrorHandlingTaskExecutor)) {
            ErrorHandler errorHandler = ChannelUtils.getErrorHandler(getBeanFactory());
            this.executor = new ErrorHandlingTaskExecutor(this.executor, errorHandler);
        }
        UnicastingDispatcher unicastingDispatcher = new UnicastingDispatcher(this.executor);
        unicastingDispatcher.setFailover(this.failover);
        if (this.maxSubscribers == null) {
            this.maxSubscribers = getIntegrationProperty(IntegrationProperties.CHANNELS_MAX_UNICAST_SUBSCRIBERS,
                    Integer.class);
        }
        unicastingDispatcher.setMaxSubscribers(this.maxSubscribers);
        if (this.loadBalancingStrategy != null) {
            unicastingDispatcher.setLoadBalancingStrategy(this.loadBalancingStrategy);
        }

        unicastingDispatcher.setMessageHandlingTaskDecorator(task -> {
            if (ExecutorChannel.this.executorInterceptorsSize > 0) {
                return new MessageHandlingTask(task);
            } else {
                return task;
            }
        });

        this.dispatcher = unicastingDispatcher;
    }

}