org.polymap.rap.openlayers.util.ProxyServlet.java Source code

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Here is the source code for org.polymap.rap.openlayers.util.ProxyServlet.java

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/*
 * polymap.org
 * Copyright 2009, Polymap GmbH, and individual contributors as indicated
 * by the @authors tag.
 *
 * This 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 3 of
 * the License, or (at your option) any later version.
 *
 * This software 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 software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 *
 */

package org.polymap.rap.openlayers.util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.Arrays;
import java.util.List;
import java.util.zip.GZIPOutputStream;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.io.IOUtils;

/**
 * For JavaScript security reasons ( cross domain ) we sometimes 
 * need a proxy to load data ( e.g. for WFS )
 * This servlet is suposed to be a replacement for the proxy.cgi provided
 * by OpenLayers which is written in python. This Servlet (written in Java) fits
 * better into the RAP enviroment. 
 * 
 * @author Marcus -LiGi- B&uuml;schleb < mail: ligi (at) polymap (dot) de >
 * 
 */

public class ProxyServlet extends HttpServlet {

    private static final long serialVersionUID = -6526120143460180643L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doProxy(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // TODO checkme - only GET is tested right now
        doProxy(request, response);
    }

    private void doProxy(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        if (getServletConfig().getInitParameter("host_list") == null) {
            response.sendError(HttpServletResponse.SC_BAD_REQUEST, "There is no Host-List for this Servlet");
            return;

        }

        List<String> host_list = Arrays.asList(getServletConfig().getInitParameter("host_list").split(","));

        String url_param = null;
        url_param = request.getParameter("url");

        if (url_param == null) {
            response.sendError(HttpServletResponse.SC_BAD_REQUEST, "URL Parameter Missing");
            return;
        }

        try {
            URL url = new URL(url_param);

            /* Check if the host is in the list of allowed hosts */
            if (!host_list.contains(url.getHost())) {
                response.sendError(HttpServletResponse.SC_BAD_REQUEST,
                        "URL Parameter Bad - the Host " + url.getHost() + " is not in my list of valid Hosts!");
                return;
            }

            URLConnection con = url.openConnection();

            if (con.getContentType() != null)
                response.setContentType(con.getContentType());
            else
                response.setContentType("text/xml");

            /* check if the client accepts gzip Encoding */
            boolean client_accepts_gzip = false; // be pessimistic

            if (request.getHeader("Accept-Encoding") != null) {
                List<String> encoding_list = Arrays.asList(request.getHeader("Accept-Encoding").split(","));
                client_accepts_gzip = (encoding_list.contains("gzip"));
            }
            response.setDateHeader("Date", System.currentTimeMillis());

            if (client_accepts_gzip) {
                response.setHeader("Content-Encoding", "gzip");
                ByteArrayOutputStream output_to_tmp = new ByteArrayOutputStream();
                IOUtils.copy(url.openStream(), output_to_tmp);

                OutputStream output_to_response = new GZIPOutputStream(response.getOutputStream());
                output_to_response.write(output_to_tmp.toByteArray());
                output_to_response.close();

            } else { // client will not accept gzip -> dont compress
                IOUtils.copy(url.openStream(), response.getOutputStream());
            }

        } catch (IOException e) {
            System.out.println("Err" + e);
            response.sendError(HttpServletResponse.SC_NOT_FOUND, "Err:" + e);
        }

    }
}