URLChecker.java

/*******************************************************************************
 * Copyright (c) 2012-2017 Codenvy, S.A.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.plugin.urlfactory;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.inject.Singleton;
import javax.validation.constraints.NotNull;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.concurrent.TimeUnit;

import static java.util.Objects.requireNonNull;

/**
 * Manages checking if URL are there or not
 *
 * @author Florent Benoit
 */
@Singleton
public class URLChecker {

    /**
     * Logger.
     */
    private static final Logger LOG = LoggerFactory.getLogger(URLChecker.class);

    /**
     * Connection timeout of 10seconds.
     */
    private static final int CONNECTION_TIMEOUT = (int)TimeUnit.SECONDS.toMillis(10);

    /**
     * Error message to log.
     */
    private static final String UNABLE_TO_CHECK_MESSAGE = "Unable to check if remote location {0} is available or not. {1}";

    /**
     * Check if given URL location exists remotely
     *
     * @param url
     *         the URL to test
     * @return true if remote URL is existing directly (no redirect)
     */
    public boolean exists(@NotNull final String url) {
        requireNonNull(url, "URL parameter cannot be null");
        try {
            return exists(new URL(url));
        } catch (MalformedURLException e) {
            LOG.debug(UNABLE_TO_CHECK_MESSAGE, url, e);
            return false;
        }
    }

    /**
     * Check if given URL location exists remotely
     *
     * @param url
     *         the URL to test
     * @return true if remote URL is existing directly (no redirect)
     */
    public boolean exists(@NotNull final URL url) {
        requireNonNull(url, "URL parameter cannot be null");

        try {
            final URLConnection urlConnection = url.openConnection();
            urlConnection.setConnectTimeout(CONNECTION_TIMEOUT);
            if (urlConnection instanceof HttpURLConnection) {
                return exists((HttpURLConnection)urlConnection);
            } else {
                urlConnection.connect();
                return true;
            }
        } catch (IOException ioe) {
            LOG.debug(UNABLE_TO_CHECK_MESSAGE, url, ioe);
            return false;
        }
    }

    /**
     * Check if given URL location exists remotely
     *
     * @param httpURLConnection
     *         the http url connection to test
     * @return true if remote URL is existing directly (no redirect)
     */
    protected boolean exists(final HttpURLConnection httpURLConnection) {
        try {
            return httpURLConnection.getResponseCode() == HttpURLConnection.HTTP_OK;
        } catch (IOException ioe) {
            LOG.debug(UNABLE_TO_CHECK_MESSAGE, httpURLConnection, ioe);
            return false;
        } finally {
            httpURLConnection.disconnect();
        }
    }


}