com.bigrocksoftware.metarparser.MetarFetcher.java Source code

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Here is the source code for com.bigrocksoftware.metarparser.MetarFetcher.java

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/*
jWeather(TM) is a Java library for parsing raw weather data
Copyright (C) 2004 David Castro
    
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
    
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.
    
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    
For more information, please email arimus@users.sourceforge.net
*/
package com.bigrocksoftware.metarparser;

import java.io.*;
import java.net.*;
import org.apache.log4j.Logger;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpMethod;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.HttpRecoverableException;
import org.apache.commons.httpclient.methods.GetMethod;

/**
 * Responsible for downloading the METAR reports 
 *
 * <p>
 * <code>
 * String metarData = MetarFetcher.fetch("KLAX");<br>
 * </code>
 * </p>
 *
 * @author David Castro, dcastro@apu.edu
 * @version $Revision: 1.4 $
 * @see <a href="Metar.html">Metar</a>
 */
public class MetarFetcher {
    private static Logger log = null;
    private static String metarData = null;

    final static String httpMetarURL = "http://weather.noaa.gov/pub/data/observations/metar/stations/";
    //final static String httpMetarHostname =  "weather.noaa.gov";
    //final static int    httpMetarPort     =  80;
    //final static String httpMetarPath     = "/pub/data/observations/metar/stations/";

    static {
        log = Logger.getLogger("net.sf.jweather");
        log.debug("MetarFetcher: instantiated");
    }

    public static String fetch(String station) {
        return fetch(station, 0);
    }

    public static String fetch(String station, int timeout) {
        metarData = null;

        // create the http client
        HttpClient client = new HttpClient();

        // set the timeout is specified
        if (timeout != 0) {
            log.debug("MetarFetch: setting timeout to '" + timeout + "' milliseconds");
            long start = System.currentTimeMillis();
            client.setConnectionTimeout(timeout);
            long end = System.currentTimeMillis();
            if (end - start < timeout) {
                client.setTimeout((int) (end - start));
            } else {
                return null;
            }
        }

        // create the http method we will use
        HttpMethod method = new GetMethod(httpMetarURL + station + ".TXT");

        // connect to the NOAA site, retrying up to the specified num
        int statusCode = -1;
        //for (int attempt = 0; statusCode == -1 && attempt < 3; attempt++) {
        try {
            // execute the get method
            log.debug("MetarFetcher: downloading data for station '" + station + "'");
            statusCode = client.executeMethod(method);
        } catch (HttpRecoverableException e) {
            log.error("a recoverable exception occurred, " + "retrying." + e.getMessage());
        } catch (IOException e) {
            log.error("failed to download file: " + e);
        }
        //}

        // check that we didn't run out of retries
        if (statusCode != HttpStatus.SC_OK) {
            log.error("failed to download station data for '" + station + "'");
            return null;
        } else {
            // read the response body
            byte[] responseBody = method.getResponseBody();

            // release the connection
            method.releaseConnection();

            // deal with the response.
            // FIXME - ensure we use the correct character encoding here
            metarData = new String(responseBody) + "\n";
            log.debug("MetarFetcher: metar data: " + metarData);
        }

        return metarData;
    }
}