Download.java

/*
   Copyright 2013 Nationale-Nederlanden

   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 nl.nn.adapterframework.webcontrol;

import java.io.IOException;
import java.net.URLEncoder;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

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

import nl.nn.adapterframework.util.LogUtil;

import org.apache.log4j.Logger;

/**
 * Servlet that redirects a POST that should result in a download to a GET without parameters.
 * This is to work around an issue in Internet Explorer 6 that does not allow downloading from https POSTS.
 * 
 * @author  Gerrit van Brakel
 * @since   4.9.8
 */
public class Download extends HttpServlet {
	protected static Logger log = LogUtil.getLogger(Download.class);

	
	public static final String MY_OWN_URL="/Download";
	public static final String URL_KEY="downloadurl";
	public static final String PARAMETERS_KEY="downloadparameters";
	public static final String FILENAME_KEY="downloadfilename";
	public static final String CONTENTTYPE_KEY="downloadcontenttype";

	public static boolean redirectForDownload(HttpServletRequest request, HttpServletResponse response, String contentType, String filename) throws IOException {
		if (!(request.getMethod().equalsIgnoreCase("POST") && request.getScheme().equals("https")) ) {
			// TODO could test for GET with paramters, too
			return false;
		}

		if (log.isDebugEnabled()) log.debug("redirecting to GET Download, to avoid IE 6 problems with download via https POST");
		String url=request.getRequestURI();
		Map params=new LinkedHashMap();
		
		for (Enumeration enumeration=request.getParameterNames();enumeration.hasMoreElements();) {
			String name=(String)enumeration.nextElement();
			String values[]=request.getParameterValues(name);
			params.put(name,values);
		}
		HttpSession session=request.getSession(true);
		session.setAttribute(URL_KEY,url);
		session.setAttribute(PARAMETERS_KEY,params);
		session.setAttribute(FILENAME_KEY,filename);
		session.setAttribute(CONTENTTYPE_KEY,contentType);
		response.sendRedirect(request.getContextPath()+MY_OWN_URL);
		return true;
	}


	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		HttpSession session=request.getSession();
		if (session!=null) {
			String url = (String)session.getAttribute(URL_KEY);
			if (url!=null) {
				String parameters=null;
				Map params=(Map)session.getAttribute(PARAMETERS_KEY);
				for (Iterator it=params.keySet().iterator(); it.hasNext();) {
					String name=(String)it.next();
					String values[]=(String[])params.get(name);
					for (int i=0; i<values.length; i++) {
						if (parameters==null) {
							parameters="?";
						} else {
							parameters+="&";
						}
						parameters+=name+"="+URLEncoder.encode(values[i],response.getCharacterEncoding());
					}
				}
				if (parameters!=null) {
					url+=parameters;
				}
				String context=request.getContextPath();
				if (url.startsWith(context)) {
					url=url.substring(context.length());
				}
				url=response.encodeURL(url);
				if (log.isDebugEnabled()) log.debug("dispatching to ["+url+"]");
				String contenttype=(String)session.getAttribute(CONTENTTYPE_KEY);
				String filename=(String)session.getAttribute(FILENAME_KEY);
				
				session.removeAttribute(URL_KEY);
				session.removeAttribute(PARAMETERS_KEY);
				session.removeAttribute(CONTENTTYPE_KEY);
				session.removeAttribute(FILENAME_KEY);
				
				response.setContentType(contenttype);
				response.setHeader("Content-Disposition","attachment; filename=\""+filename+"\"");
				RequestDispatcher rd=request.getRequestDispatcher(url);
				rd.include(request,response);
			}
		}
	}

}