/*

  * Copyright 2005-2008 The Kuali Foundation

  * 

  * 

  * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php

  * 

  * 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 org.kuali.rice.core.web;

 import java.io.IOException;

 import java.text.MessageFormat;

 import java.util.Enumeration;

 import java.util.LinkedHashMap;

 import java.util.Map;

 import java.util.regex.Matcher;

 import java.util.regex.Pattern;

 import javax.servlet.RequestDispatcher;

 import javax.servlet.ServletConfig;

 import javax.servlet.ServletException;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 /**

  * Servlet that forwards requests via the RequestDispatcher based on regular expression

  * matching and replacement on the URI

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 public class RequestForwardingServlet extends HttpServlet {

     private LinkedHashMap<Pattern, MessageFormat> forwardTable = new LinkedHashMap<Pattern, MessageFormat>();

     @Override

     public void init() throws ServletException {

         super.init();

         ServletConfig cfg = getServletConfig();

         Enumeration paramNames = cfg.getInitParameterNames(); 

         while (paramNames.hasMoreElements()) {

             String name = (String) paramNames.nextElement();

             Pattern pattern = Pattern.compile(name);

             String forwardPath = cfg.getInitParameter(name);

             MessageFormat messageFormat = new MessageFormat(forwardPath);

             forwardTable.put(pattern, messageFormat);

         }

     }

     @Override

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

         String requestURI = request.getRequestURI();

         for (Map.Entry<Pattern, MessageFormat> entry: forwardTable.entrySet()) {

             Pattern pattern = entry.getKey();

             Matcher matcher = pattern.matcher(requestURI);

             if (matcher.matches()) {

                 Object[] params = new Object[matcher.groupCount()];

                 for (int i = 0; i < params.length; i++) {

                     params[i] = matcher.group(i + 1); // offset by 1 because group at index 0 denotes the "entire pattern" 

                 }

                 String forwardPath = entry.getValue().format(params);

                 RequestDispatcher rd = request.getRequestDispatcher(forwardPath);

                 if (rd == null) {

                     response.sendError(HttpServletResponse.SC_NOT_FOUND, "Internal resource '" + forwardPath + "' not found");

                 } else {

                     rd.forward(request, response);

                 }

                 return;

             }

         }

     }

 }