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1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *  
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *  
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License. 
18   *  
19   */
20  package org.apache.directory.server.core.invocation;
21  
22  
23  import java.util.ArrayList;
24  import java.util.Collections;
25  import java.util.IdentityHashMap;
26  import java.util.List;
27  import java.util.Map;
28  
29  import org.apache.directory.server.core.interceptor.context.OperationContext;
30  
31  
32  /**
33   * Keeps track of recursive {@link Invocation}s.  This stack assumes an invocation
34   * occurs in the same thread since it is called first, so we manages stacks
35   * for each invocation in {@link ThreadLocal}-like manner.  You can just use
36   * {@link #getInstance()} to get current invocation stack.
37   * 
38   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
39   * @version $Rev: 662440 $, $Date: 2008-06-02 16:00:23 +0200 (Mo, 02 Jun 2008) $
40   */
41  public final class InvocationStack
42  {
43      // I didn't use ThreadLocal to release contexts explicitly.
44      // It seems like JDK 1.5 supports explicit release by introducing
45      // <tt>ThreadLocal.remove()</tt>, but we're still targetting 1.4.
46      private static final Map<Thread, InvocationStack> stacks = 
47          Collections.synchronizedMap( new IdentityHashMap<Thread, InvocationStack>() );
48  
49      private final Thread thread;
50      private final List<OperationContext> stack = new ArrayList<OperationContext>();
51  
52      
53      /**
54       * Returns the invocation stack of current thread.
55       */
56      public static InvocationStack getInstance()
57      {
58          Thread currentThread = Thread.currentThread();
59          InvocationStack ctx;
60          ctx = stacks.get( currentThread );
61  
62          if ( ctx == null )
63          {
64              ctx = new InvocationStack( currentThread );
65          }
66  
67          return ctx;
68      }
69      
70  
71      private InvocationStack( Thread currentThread )
72      {
73          thread = currentThread;
74          stacks.put( currentThread, this );
75      }
76  
77  
78      /**
79       * Returns an array of {@link Invocation}s.  0th element is the
80       * latest invocation.
81       */
82      public OperationContext[] toArray()
83      {
84          OperationContext[] result = new OperationContext[stack.size()];
85          result = stack.toArray( result );
86          return result;
87      }
88  
89  
90      /**
91       * Returns the latest invocation.
92       */
93      public OperationContext peek()
94      {
95          return stack.get( 0 );
96      }
97  
98  
99      /**
100      * Returns true if the stack is empty false otherwise.
101      */
102     public boolean isEmpty()
103     {
104         return stack.isEmpty();
105     }
106 
107 
108     /**
109      * Pushes the specified invocation to this stack.
110      */
111     public void push( OperationContext opContext )
112     {
113         stack.add( 0, opContext );
114     }
115 
116 
117     /**
118      * Pops the latest invocation from this stack.  This stack is released
119      * automatically if you pop all items from this stack.
120      */
121     public OperationContext pop()
122     {
123         OperationContext invocation = stack.remove( 0 );
124         
125         if ( stack.size() == 0 )
126         {
127             stacks.remove( thread );
128         }
129 
130         return invocation;
131     }
132 }