com.devnexus.ting.core.service.impl.DefaultTwitterService.java Source code

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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 com.devnexus.ting.core.service.impl;

import java.util.Collection;
import java.util.Comparator;
import java.util.SortedSet;
import java.util.TreeSet;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.messaging.simp.SimpMessageSendingOperations;
import org.springframework.social.twitter.api.Tweet;
import org.springframework.stereotype.Service;

import com.devnexus.ting.core.service.TwitterService;
import com.devnexus.ting.model.TwitterMessage;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

/**
 * Implementation of the TwitterService interface.
 *
 * @author Gunnar Hillert
 * @since 1.0
 *
 */
@Service
public class DefaultTwitterService implements TwitterService {

    /** Holds a collection of polled Twitter messages */
    private volatile LoadingCache<Long, TwitterMessage> twitterMessages;

    @Autowired
    private SimpMessageSendingOperations messagingTemplate;

    /**
     * Constructor that initializes the 'twitterMessages' Map as a simple LRU
     * cache holding a maximum of 20 messages.
     */
    public DefaultTwitterService() {

        this.twitterMessages = CacheBuilder.newBuilder().maximumSize(40)
                .build(new CacheLoader<Long, TwitterMessage>() {
                    public TwitterMessage load(Long key) {
                        return null;
                    }
                });
    }

    /** {@inheritDoc} */
    @Override
    public Collection<TwitterMessage> getTwitterMessages() {
        SortedSet<TwitterMessage> twitterMessages = new TreeSet<TwitterMessage>(new Comparator<TwitterMessage>() {
            @Override
            public int compare(TwitterMessage twitterMessage1, TwitterMessage twitterMessage2) {
                return twitterMessage2.getCreatedAt().compareTo(twitterMessage1.getCreatedAt());
            }
        });

        twitterMessages.addAll(this.twitterMessages.asMap().values());
        return twitterMessages;
    }

    /**
     * Called by Spring Integration to populate a simple LRU cache.
     *
     * @param tweet - The Spring Integration tweet object.
     */
    public void addTwitterMessages(Tweet tweet) {

        final TwitterMessage twitterMessage = new TwitterMessage(tweet.getCreatedAt(), tweet.getText(),
                tweet.getFromUser(), tweet.getProfileImageUrl());
        this.twitterMessages.put(tweet.getCreatedAt().getTime(), twitterMessage);
        messagingTemplate.convertAndSend("/queue/tweets", twitterMessage);
    }

}