org.springframework.integration.aggregator.SequenceSizeReleaseStrategy.java Source code

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Here is the source code for org.springframework.integration.aggregator.SequenceSizeReleaseStrategy.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.aggregator;

import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;

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

import org.springframework.integration.IntegrationMessageHeaderAccessor;
import org.springframework.integration.store.MessageGroup;
import org.springframework.messaging.Message;

/**
 * An implementation of {@link ReleaseStrategy} that simply compares the current size of
 * the message list to the expected 'sequenceSize'. Supports release of partial sequences.
 * Correlating message handlers prevent the addition of duplicate sequences to the group.
 *
 * @author Mark Fisher
 * @author Marius Bogoevici
 * @author Dave Syer
 * @author Iwein Fuld
 * @author Oleg Zhurakousky
 * @author Artem Bilan
 * @author Enrique Rodr?guez
 */
public class SequenceSizeReleaseStrategy implements ReleaseStrategy {

    private static final Log logger = LogFactory.getLog(SequenceSizeReleaseStrategy.class);

    private final Comparator<Message<?>> comparator = new MessageSequenceComparator();

    private volatile boolean releasePartialSequences;

    /**
     * Construct an instance that does not support releasing partial sequences.
     */
    public SequenceSizeReleaseStrategy() {
        this(false);
    }

    /**
     * Construct an instance that supports releasing partial sequences if
     * releasePartialSequences is true. This can be an expensive operation on large
     * groups.
     * @param releasePartialSequences true to allow the release of partial sequences.
     */
    public SequenceSizeReleaseStrategy(boolean releasePartialSequences) {
        this.releasePartialSequences = releasePartialSequences;
    }

    /**
     * Flag that determines if partial sequences are allowed. If true then as soon as
     * enough messages arrive that can be ordered they will be released, provided they
     * all have sequence numbers greater than those already released.
     * This can be an expensive operation for large groups.
     * @param releasePartialSequences true when partial sequences should be released.
     */
    public void setReleasePartialSequences(boolean releasePartialSequences) {
        this.releasePartialSequences = releasePartialSequences;
    }

    @Override
    public boolean canRelease(MessageGroup messageGroup) {

        boolean canRelease = false;

        int size = messageGroup.size();
        if (this.releasePartialSequences && size > 0) {
            if (logger.isTraceEnabled()) {
                logger.trace("Considering partial release of group [" + messageGroup + "]");
            }
            Collection<Message<?>> messages = messageGroup.getMessages();
            Message<?> minMessage = Collections.min(messages, this.comparator);

            int nextSequenceNumber = new IntegrationMessageHeaderAccessor(minMessage).getSequenceNumber();
            int lastReleasedMessageSequence = messageGroup.getLastReleasedMessageSequenceNumber();

            if (nextSequenceNumber - lastReleasedMessageSequence == 1) {
                canRelease = true;
            }
        } else {
            if (size == 0) {
                canRelease = true;
            } else {
                int sequenceSize = messageGroup.getSequenceSize();
                // If there is no sequence then it must be incomplete....
                if (sequenceSize == size) {
                    canRelease = true;
                }
            }
        }
        return canRelease;
    }

}