org.springframework.messaging.simp.handler.UserDestinationMessageHandler.java Source code

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Here is the source code for org.springframework.messaging.simp.handler.UserDestinationMessageHandler.java

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/*
 * Copyright 2002-2013 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
 *
 * http://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.messaging.simp.handler;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHandler;
import org.springframework.messaging.MessagingException;
import org.springframework.messaging.core.MessageSendingOperations;
import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
import org.springframework.messaging.simp.SimpMessageType;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.util.Assert;

/**
 * Supports destinations prefixed with "/user/{username}", transforms the
 * destination to a unique queue to which the user is subscribed, and then sends
 * the message for further processing.
 *
 * <p>The target destination has the prefix removed and a unique queue suffix,
 * resolved via {@link #setUserQueueSuffixResolver(UserQueueSuffixResolver)}, appended.
 * For example a destination such as "/user/john/queue/trade-confirmation" could
 * be transformed to "/queue/trade-confirmation/i9oqdfzo".
 *
 * @author Rossen Stoyanchev
 * @since 4.0
 */
public class UserDestinationMessageHandler implements MessageHandler {

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

    private final MessageSendingOperations<String> messagingTemplate;

    private String destinationPrefix = "/user/";

    private UserQueueSuffixResolver userQueueSuffixResolver = new SimpleUserQueueSuffixResolver();

    /**
     *
     * @param messagingTemplate
     * @param resolver the resolver to use to find queue suffixes for a user
     */
    public UserDestinationMessageHandler(MessageSendingOperations<String> messagingTemplate,
            UserQueueSuffixResolver userQueueSuffixResolver) {

        Assert.notNull(messagingTemplate, "messagingTemplate is required");
        Assert.notNull(userQueueSuffixResolver, "userQueueSuffixResolver is required");

        this.messagingTemplate = messagingTemplate;
        this.userQueueSuffixResolver = userQueueSuffixResolver;
    }

    /**
     * <p>The default prefix is "/user".
     * @param prefix the prefix to set
     */
    public void setDestinationPrefix(String prefix) {
        Assert.hasText(prefix, "prefix is required");
        this.destinationPrefix = prefix.endsWith("/") ? prefix : prefix + "/";
    }

    /**
     * @return the prefix
     */
    public String getDestinationPrefix() {
        return this.destinationPrefix;
    }

    /**
     * @return the resolver for queue suffixes for a user
     */
    public UserQueueSuffixResolver getUserQueueSuffixResolver() {
        return this.userQueueSuffixResolver;
    }

    /**
     * @return the messagingTemplate
     */
    public MessageSendingOperations<String> getMessagingTemplate() {
        return this.messagingTemplate;
    }

    @Override
    public void handleMessage(Message<?> message) throws MessagingException {

        SimpMessageHeaderAccessor headers = SimpMessageHeaderAccessor.wrap(message);
        SimpMessageType messageType = headers.getMessageType();
        String destination = headers.getDestination();

        if (!SimpMessageType.MESSAGE.equals(messageType)) {
            return;
        }

        if (!checkDestination(destination)) {
            return;
        }

        if (logger.isTraceEnabled()) {
            logger.trace("Processing message to destination " + destination);
        }

        UserDestinationParser destinationParser = new UserDestinationParser(destination);
        String user = destinationParser.getUser();

        if (user == null) {
            if (logger.isErrorEnabled()) {
                logger.error("Ignoring message, expected destination pattern \"" + this.destinationPrefix
                        + "{userId}/**\": " + destination);
            }
            return;
        }

        for (String sessionId : this.userQueueSuffixResolver.getUserQueueSuffixes(user)) {

            String targetDestination = destinationParser.getTargetDestination(sessionId);
            headers.setDestination(targetDestination);
            message = MessageBuilder.withPayloadAndHeaders(message.getPayload(), headers).build();

            if (logger.isTraceEnabled()) {
                logger.trace("Sending message to resolved target destination " + targetDestination);
            }
            this.messagingTemplate.send(targetDestination, message);
        }
    }

    private boolean checkDestination(String destination) {
        if (destination != null) {
            if (destination.startsWith(this.destinationPrefix)) {
                return true;
            }
        }
        return false;
    }

    private class UserDestinationParser {

        private final String user;

        private final String targetDestination;

        public UserDestinationParser(String destination) {

            int userStartIndex = destinationPrefix.length();
            int userEndIndex = destination.indexOf('/', userStartIndex);

            if (userEndIndex > 0) {
                this.user = destination.substring(userStartIndex, userEndIndex);
                this.targetDestination = destination.substring(userEndIndex);
            } else {
                this.user = null;
                this.targetDestination = null;
            }
        }

        public String getUser() {
            return this.user;
        }

        public String getTargetDestination(String sessionId) {
            return (this.targetDestination != null) ? this.targetDestination + sessionId : null;
        }
    }

}