WebRenderServlet


1   /* 
2    * This file is part of the Echo Web Application Framework (hereinafter "Echo").
3    * Copyright (C) 2002-2005 NextApp, Inc.
4    *
5    * Version: MPL 1.1/GPL 2.0/LGPL 2.1
6    *
7    * The contents of this file are subject to the Mozilla Public License Version
8    * 1.1 (the "License"); you may not use this file except in compliance with
9    * the License. You may obtain a copy of the License at
10   * http://www.mozilla.org/MPL/
11   *
12   * Software distributed under the License is distributed on an "AS IS" basis,
13   * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
14   * for the specific language governing rights and limitations under the
15   * License.
16   *
17   * Alternatively, the contents of this file may be used under the terms of
18   * either the GNU General Public License Version 2 or later (the "GPL"), or
19   * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
20   * in which case the provisions of the GPL or the LGPL are applicable instead
21   * of those above. If you wish to allow use of your version of this file only
22   * under the terms of either the GPL or the LGPL, and not to allow others to
23   * use your version of this file under the terms of the MPL, indicate your
24   * decision by deleting the provisions above and replace them with the notice
25   * and other provisions required by the GPL or the LGPL. If you do not delete
26   * the provisions above, a recipient may use your version of this file under
27   * the terms of any one of the MPL, the GPL or the LGPL.
28   */
29  
30  package nextapp.echo2.webrender;
31  
32  import java.io.IOException  ;
33  
34  import javax.servlet.ServletException  ;
35  import javax.servlet.http.HttpServlet  ;
36  import javax.servlet.http.HttpServletRequest  ;
37  import javax.servlet.http.HttpServletResponse  ;
38  
39  import nextapp.echo2.webrender.service.CoreServices;
40  import nextapp.echo2.webrender.service.DebugPaneService;
41  
42  /**
43   * Echo <code>HttpServlet</code> implementation.
44   */
45  public abstract class WebRenderServlet extends HttpServlet   {
46      
47      /** 
48       * A <code>ThreadLocal</code> reference to the 
49       * <code>Connection</code> relevant to the current thread.
50       */ 
51      private static final ThreadLocal   activeConnection = new InheritableThreadLocal  ();
52      
53      /**
54       * A flag indicating whether caching should be disabled for all services.
55       * This flag is for testing purposes only, and should be disabled for
56       * production use.
57       */
58      public static final boolean DISABLE_CACHING = false;
59      
60      /**
61       * Request parameter identifying requested <code>Service</code>.
62       */
63      public static final String   SERVICE_ID_PARAMETER = "serviceId";
64      
65      /**
66       * <code>Service</code> identifier of the 'default' service. 
67       * The 'default' service is rendered when a client makes a request
68       * without a service identifier and a session DOES exist.
69       */
70      public static final String   SERVICE_ID_DEFAULT = "Echo.Default";
71      
72      /**
73       * <code>Service</code> identifier of the 'new instance' service. 
74       * The 'new instance' service is rendered when a client makes a request
75       * without a service identifier and a session DOES NOT exist..
76       */
77      public static final String   SERVICE_ID_NEW_INSTANCE = "Echo.NewInstance";
78      
79      /**
80       * <code>Service</code> identifier of the 'session expired' service.
81       * The 'session expired' service is rendered when a client makes a
82       * request that has an identifier and is intended for an active session, 
83       * but no session exists. 
84       */
85      public static final String   SERVICE_ID_SESSION_EXPIRED = "Echo.Expired";
86      
87      /**
88       * Global handler for multipart/form-data encoded HTTP requests.
89       */
90      private static MultipartRequestWrapper multipartRequestWrapper;
91      
92      private static final long startupTime = System.currentTimeMillis();
93      
94      /**
95       * Global <code>ServiceRegistry</code>.
96       */
97      private static final ServiceRegistry services = new ServiceRegistry();
98  
99      static {
100         CoreServices.install(services);
101         services.add(DebugPaneService.INSTANCE);
102     }
103     
104     /**
105      * An interface implemented by a supporting object that will handle 
106      * multipart/form-data encoded HTTP requests.  This type of request is
107      * required for file uploads.  Echo does not provide internal support
108      * for file uploads, but instead provides hooks for file-upload handling
109      * components.  
110      */
111     public static interface MultipartRequestWrapper {
112     
113         /**
114          * Returns a replacement <code>HttpServletRequest</code> object that
115          * may be used to handle a multipart/form-data encoded HTTP request.
116          *
117          * @param request The HTTP request provided from the servlet container
118          *        that has multipart/form-data encoding.
119          * @return An HTTP request that is capable of handling 
120          *         multipart/form-data encoding.
121          */
122         public HttpServletRequest   getWrappedRequest(HttpServletRequest   request)
123         throws IOException  , ServletException  ;
124     }
125 
126     /**
127      * Returns a reference to the <code>Connection</code> that is 
128      * relevant to the current thread, or null if no connection is relevant.
129      * 
130      * @return the relevant <code>Connection</code>
131      */
132     public static final Connection getActiveConnection() {
133         return (Connection) activeConnection.get();
134     }
135     
136     /**
137      * Returns the multipart/form-data encoded HTTP request handler.
138      * 
139      * @return The multipart/form-data encoded HTTP request handler.
140      * @see #setMultipartRequestWrapper
141      */
142     public static MultipartRequestWrapper getMultipartRequestWrapper() {
143         return multipartRequestWrapper;
144     }
145     
146     /**
147      * Sets the multipart/form-data encoded HTTP request handler.
148      * The multipart request wrapper can only be set one time.  It should be set
149      * in a static block of your Echo application.  This method will disregard
150      * additional attempts to set the wrapper if the provided wrapper's class
151      * is identical to the existing one.  If the wrapper is already set and the
152      * new wrapper object's class is different or the wrapper is null, an
153      * exception is thrown.
154      *
155      * @param multipartRequestWrapper The handler for multipart/form-data 
156      *        encoded HTTP requests.
157      * @throws IllegalStateException if the application attempts to change
158      *        a previously set multipart request handler.
159      */
160     public static final void setMultipartRequestWrapper(MultipartRequestWrapper multipartRequestWrapper) {
161         if (WebRenderServlet.multipartRequestWrapper == null) {
162             WebRenderServlet.multipartRequestWrapper = multipartRequestWrapper;
163         } else {
164             if (multipartRequestWrapper == null || 
165                     !WebRenderServlet.multipartRequestWrapper.getClass().getName().equals(
166                     multipartRequestWrapper.getClass().getName())) {
167                 throw new IllegalStateException  ("MultipartRequestWrapper already set.");
168             }
169         }
170     }
171     
172     /**
173      * Handles a GET request.
174      *
175      * @see #process(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
176      */
177     public final void doGet(HttpServletRequest   request, HttpServletResponse   response) 
178     throws IOException  , ServletException   {
179         process(request, response);
180     }
181     
182     /**
183      * Handles a POST request.
184      *
185      * @see #process(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
186      */
187     public final void doPost(HttpServletRequest   request, HttpServletResponse   response) 
188     throws IOException  , ServletException   {
189         process(request, response);
190     }
191     
192     /**
193      * Returns the service that corresponds to the specified Id.
194      *
195      * @param id The id of the service to return.
196      * @return The service corresponding to the specified Id.
197      */
198     private static Service getService(UserInstance userInstance, String   id) {
199         Service service;
200         
201         service = services.get(id);
202         if (id == null) {
203             if (userInstance == null) {
204                 id = SERVICE_ID_NEW_INSTANCE;
205             } else {
206                 id = SERVICE_ID_DEFAULT;
207             }
208         } else {
209             if (userInstance == null) {
210                 id = SERVICE_ID_SESSION_EXPIRED;
211             }
212         }
213         
214         service = services.get(id);
215 
216         if (service == null) {
217             if (SERVICE_ID_DEFAULT.equals(id)) {
218                 throw new RuntimeException  ("Service not registered: SERVICE_ID_DEFAULT");
219             } else if (SERVICE_ID_NEW_INSTANCE.equals(id)) {
220                 throw new RuntimeException  ("Service not registered: SERVICE_ID_NEW_INSTANCE");
221             } else if (SERVICE_ID_SESSION_EXPIRED.equals(id)) {
222                 throw new RuntimeException  ("Service not registered: SERVICE_ID_SESSION_EXPIRED");
223             }
224         }
225         
226         return service;
227     }
228     
229     /**
230      * Retrieves the global <code>ServiceRegistry</code>.
231      * 
232      * @return The global <code>ServiceRegistry</code>.
233      */
234     public static ServiceRegistry getServiceRegistry() {
235         return services;
236     }
237     
238     /**
239      * Processes a HTTP request and generates a response.
240      * 
241      * @param request the incoming <code>HttpServletRequest</code>
242      * @param response the outgoing <code>HttpServletResponse</code>
243      */
244     protected void process(HttpServletRequest   request, HttpServletResponse   response) 
245     throws IOException  , ServletException   {
246         Connection conn = null;
247         try {
248             conn = new Connection(this, request, response);
249             activeConnection.set(conn);
250             String   serviceId = request.getParameter(SERVICE_ID_PARAMETER);
251             Service service = getService(conn.getUserInstance(), serviceId);
252             if (service == null) {
253                 throw new ServletException  ("Service id \"" + serviceId + "\" not registered.");
254             }
255             int version = service.getVersion();
256             
257             // Set caching directives.
258             if ((!DISABLE_CACHING) && version != Service.DO_NOT_CACHE) {
259                 // Setting all of the following (possibly with the exception of "Expires")
260                 // are *absolutely critical* in order to ensure proper caching of resources
261                 // with Internet Explorer 6.  Without "Last-Modified", IE6 appears to not
262                 // cache images properly resulting in an substantially greater than expected
263                 // performance impact.
264                 response.setHeader("Cache-Control", "max-age=3600");
265                 response.setDateHeader("Expires", System.currentTimeMillis() + (86400000));
266                 response.setDateHeader("Last-Modified", startupTime);
267             } else {
268                 response.setHeader("Pragma", "no-cache");
269                 response.setHeader("Cache-Control", "no-store");
270                 response.setHeader("Expires", "0");
271             }
272             
273             service.service(conn);
274             
275         } catch (ServletException   ex) {
276             if (conn != null) {
277                 conn.disposeUserInstance();
278             }
279             throw(ex);
280         } catch (IOException   ex) {
281             if (conn != null) {
282                 conn.disposeUserInstance();
283             }
284             throw(ex);
285         } catch (RuntimeException   ex) {
286             if (conn != null) {
287                 conn.disposeUserInstance();
288             }
289             throw(ex);
290         } finally {
291             activeConnection.set(null);
292         }
293     }
294 }
295
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