package it.unimi.dsi.mg4j.query;/*		  * MG4J: Managing Gigabytes for Java * * Copyright (C) 2005-2007 Sebastiano Vigna  * *  This program 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 2 of the License, or (at your option) *  any later version. * *  This program 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 this program; if not, write to the Free Software *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * */import java.io.IOException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** An item serving a file from the file system. *  * <P>This kind of {@link it.unimi.dsi.mg4j.query.QueryServlet} item will load into the browser * the file specified by the parameter <code>uri</code>. Its only purpose is to work around security * problems that forbid in some browsers (e.g., Firefox) to link a file in  * the file system from a page retrieved from an HTTP server. *  * <P>When this class is loaded, it creates the singleton {@link it.unimi.dsi.mg4j.query.HttpFileServer} * and caches it to avoid class garbage collection. */public class FileSystemItem extends HttpServlet {	private static final long serialVersionUID = 1L;	/** The singleton file server. */	private final static HttpFileServer SERVER = HttpFileServer.getServer();	public void init() {		// This avoids class garbage collection.		getServletContext().setAttribute( "HttpFileServer", SERVER );	}		protected void doGet( final HttpServletRequest request, final HttpServletResponse response ) throws IOException {		String uri = request.getParameter( "uri" );		if ( uri != null && uri.indexOf( "file:" ) == 0 ) {			uri = uri.substring( "file:".length() );			response.setStatus( HttpServletResponse.SC_MOVED_PERMANENTLY );			response.addHeader( "location", "http://localhost:" + HttpFileServer.getPort() + uri );			return;		}				response.sendError( HttpServletResponse.SC_FORBIDDEN, "This servlet requires a parameter uri containing a URI of type file:" );	}	protected void doPost( final HttpServletRequest request, final HttpServletResponse response ) throws IOException {		doGet( request, response );	}}