DwrGuiceUtil


1   /*
2    * Copyright 2007 Tim Peierls
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.directwebremoting.guice;
17  
18  import com.google.inject.Injector;
19  
20  import java.util.LinkedList  ;
21  
22  import javax.servlet.ServletContext  ;
23  
24  import org.directwebremoting.WebContext;
25  import org.directwebremoting.WebContextFactory;
26  import static org.directwebremoting.guice.DwrGuiceServletContextListener.getPublishedInjector;
27  
28  
29  /**
30   * Utilities for making Injector and ServletContext instances available.
31   * @author Tim Peierls [tim at peierls dot net]
32   */
33  class DwrGuiceUtil
34  {
35      /**
36       * Returns the Injector instance published in the current servlet context.
37       */
38      static Injector getInjector()
39      {
40          return getPublishedInjector(getServletContext());
41      }
42  
43      /**
44       * Gets the servlet context from the current web context, if one exists,
45       * otherwise gets it from the thread-local stash.
46       */
47      static ServletContext   getServletContext()
48      {
49          WebContext webcx = WebContextFactory.get();
50          if (webcx != null)
51          {
52              return webcx.getServletContext();
53          }
54          else
55          {
56              return servletContexts.get().getFirst();
57          }
58      }
59      
60      /**
61       * Thread-locally pushes a servlet context. Call {@link #popServletContext}
62       * in a finally block when calling this method.
63       */
64      static void pushServletContext(ServletContext   context)
65      {
66          servletContexts.get().addFirst(context);
67      }
68      
69      /**
70       * Pops a thread-locally stashed servlet context. Call this in
71       * a finally block when {@link #pushServletContext} is called.
72       */
73      static void popServletContext()
74      {
75          servletContexts.get().removeFirst();
76      }
77      
78      private static final ThreadLocal  <LinkedList  <ServletContext  >> servletContexts = 
79          new ThreadLocal  <LinkedList  <ServletContext  >>()
80          {
81              protected LinkedList  <ServletContext  > initialValue()
82              {
83                  return new LinkedList  <ServletContext  >();
84              }
85          };
86  }
87
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