IpListFromUrl.java

/*******************************************************************************
 * This file is part of OpenNMS(R).
 *
 * Copyright (C) 2007-2011 The OpenNMS Group, Inc.
 * OpenNMS(R) is Copyright (C) 1999-2011 The OpenNMS Group, Inc.
 *
 * OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
 *
 * OpenNMS(R) is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation, either version 3 of the License,
 * or (at your option) any later version.
 *
 * OpenNMS(R) 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with OpenNMS(R).  If not, see:
 *      http://www.gnu.org/licenses/
 *
 * For more information contact:
 *     OpenNMS(R) Licensing <license@opennms.org>
 *     http://www.opennms.org/
 *     http://www.opennms.com/
 *******************************************************************************/

package org.opennms.core.utils;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;



/**
 * Convenience class for generating a list of IP addresses from a file URL.
 */
public class IpListFromUrl extends Object {
    /**
     * The string indicating the start of the comments in a line containing the
     * IP address in a file URL
     */
    private final static String COMMENT_STR = " #";

    /**
     * This character at the start of a line indicates a comment line in a URL
     * file
     */
    private final static char COMMENT_CHAR = '#';

    /**
     * This method is used to read all interfaces from an URL file.
     *
     * <pre>
     * The file URL is read and each entry in this file checked. Each line
     *  in the URL file can be one of -
     *  <IP><space>#<comments>
     *  or
     *  <IP>
     *  or
     *  #<comments>
     *
     *  Lines starting with a '#' are ignored and so are characters after
     *  a '<space>#' in a line.
     * </pre>
     *
     * @param url
     *            The url file to read
     * @return list of IPs in the file
     */
    public static List<String> parse(String url) {
        List<String> iplist = new ArrayList<String>();

        try {
            // open the file indicated by the url
            URL fileURL = new URL(url);

            InputStream file = fileURL.openStream();

            // check to see if the file exists
            if (file != null) {
                BufferedReader buffer = new BufferedReader(new InputStreamReader(file, "UTF-8"));

                String ipLine = null;
                String specIP = null;

                // get each line of the file and turn it into a specific range
                while ((ipLine = buffer.readLine()) != null) {
                    ipLine = ipLine.trim();
                    if (ipLine.length() == 0 || ipLine.charAt(0) == COMMENT_CHAR) {
                        // blank line or skip comment
                        continue;
                    }

                    // check for comments after IP
                    int comIndex = ipLine.indexOf(COMMENT_STR);
                    if (comIndex == -1) {
                        specIP = ipLine;
                    } else {
                        specIP = ipLine.substring(0, comIndex);
                        ipLine = ipLine.trim();
                    }

                    iplist.add(specIP);
                }

                buffer.close();
            } else {
                // log something
                log().warn("URL does not exist: " + url.toString());
            }
        } catch (MalformedURLException e) {
            log().error("Error reading URL: " + url.toString() + ": " + e.getLocalizedMessage());
        } catch (FileNotFoundException e) {
            log().error("Error reading URL: " + url.toString() + ": " + e.getLocalizedMessage());
        } catch (IOException e) {
            log().error("Error reading URL: " + url.toString() + ": " + e.getLocalizedMessage());
        }

        return iplist;
    }

    private static ThreadCategory log() {
        return ThreadCategory.getInstance(IpListFromUrl.class);
    }
}