com.sangupta.dribbble.api.DribbbleInvoker.java Source code

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Here is the source code for com.sangupta.dribbble.api.DribbbleInvoker.java

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/**
 *
 * dribbble-java-client: Java Client for Dribbble.com API
 * Copyright (c) 2012, Sandeep Gupta
 * 
 * http://www.sangupta/projects/dribbble-java-client
 * 
 * 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.sangupta.dribbble.api;

import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
import org.apache.http.util.EntityUtils;

/**
 * Utility class to invoke the end point at Dribbble.com and
 * return the HTTP response back as String.
 *  
 * @author sangupta
 *
 */
public class DribbbleInvoker {

    /**
     * My private logger
     */
    private static Logger logger = Logger.getLogger("com.sangupta.dribbble.api.DribbbleInvoker");

    /**
     * Host name for Dribbble API end points
     */
    private static final String DRIBBBLE_END_POINT = "http://api.dribbble.com/";

    /** 
     * Create an HttpClient with the ThreadSafeClientConnManager.
      * This connection manager must be used if more than one thread will
      * be using the HttpClient.
      */
    private static final ThreadSafeClientConnManager HTTP_CONNECTION_MANAGER;

    /**
     * Our reference to initialized {@link HttpClient}.
     */
    private static HttpClient httpClient = null;

    /**
     * Max rate limited requests for Dribbble.com
     */
    private static final int MAX_REQUESTS_PER_MINUTE = 60;

    /**
     * Holds the minute identifier
     */
    private static long currentRunningMinute = 0;

    /**
     * Holds the number of hits that we have made in this minute
     */
    private static int currentMinuteHitCount = 0;

    /**
     * Initialize the connection manager and create the client
     */
    static {
        HTTP_CONNECTION_MANAGER = new ThreadSafeClientConnManager();
        httpClient = new DefaultHttpClient(HTTP_CONNECTION_MANAGER);
    }

    /**
     * Invoke the final end-point for Dribbble maintaining rate-limiting connections.
     * 
     * @param endPoint
     * @param params
     * @return
     */
    public static String invokeEndPoint(String endPoint, String params, boolean throwException) {
        // build the final URL to hit upon
        if (endPoint == null || endPoint.trim().length() == 0) {
            throw new IllegalArgumentException("Dribbble endpoint cannot be null.");
        }

        String url = DRIBBBLE_END_POINT + endPoint;
        if (params != null && params.trim().length() > 0) {
            url += "?" + params;
        }

        // check for rate limiting now
        // calculations are kept out to make the critical
        // block faster
        long millis = System.currentTimeMillis();
        long seconds = millis / 1000;
        long minute = seconds / 60;

        boolean proceed = checkRateLimit(minute, throwException);

        if (!proceed) {
            return null;
        }

        // go ahead and hit the URL
        String response = hit(url);

        // return back the response
        return response;
    }

    /**
     * Method that checks for rate-limit quota for Dribbble.com currently
     * set as 60 per minute.
     */
    private static synchronized boolean checkRateLimit(long minute, boolean throwException) {
        if (minute == currentRunningMinute) {
            // we are for the same minute
            currentMinuteHitCount++;
            if (currentMinuteHitCount > MAX_REQUESTS_PER_MINUTE) {
                if (throwException) {
                    throw new DribbbleApiRateLimitException("Over the limit of 60 requests/minute... slow dow.");
                }

                return false;
            }

            return true;
        }

        // we are on switchover minute
        currentRunningMinute = minute;
        currentMinuteHitCount = 1;

        return true;
    }

    /**
     * Hit the URL endpoint and return the response body if the status code is HTTP 200.
     * 
     * @param url
     * @return
     */
    private static String hit(final String url) {
        HttpGet httpGet = new HttpGet(url);
        try {
            HttpResponse httpResponse = httpClient.execute(httpGet);
            final HttpEntity entity = httpResponse.getEntity();

            // check for success code of HTTP 200
            int responseCode = httpResponse.getStatusLine().getStatusCode();
            if (responseCode != 200) {
                // consume the entity to release connection
                EntityUtils.consume(entity);

                // return null response
                return null;
            }

            // consume the entity
            String response = EntityUtils.toString(entity);
            return response;
        } catch (ClientProtocolException e) {
            logger.log(Level.WARNING, "Unable to hit dribbble endpoint: " + url, e);
        } catch (IOException e) {
            logger.log(Level.WARNING, "Unable to hit dribbble endpoint: " + url, e);
        }

        return null;
    }
}