001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied. See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 *
019 */
020 package org.apache.directory.server.core.invocation;
021
022
023 import java.util.ArrayList;
024 import java.util.Collections;
025 import java.util.IdentityHashMap;
026 import java.util.List;
027 import java.util.Map;
028
029 import org.apache.directory.server.core.interceptor.context.OperationContext;
030
031
032 /**
033 * Keeps track of recursive {@link Invocation}s. This stack assumes an invocation
034 * occurs in the same thread since it is called first, so we manages stacks
035 * for each invocation in {@link ThreadLocal}-like manner. You can just use
036 * {@link #getInstance()} to get current invocation stack.
037 *
038 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
039 * @version $Rev: 896599 $, $Date: 2010-01-06 20:26:43 +0200 (Wed, 06 Jan 2010) $
040 */
041 public final class InvocationStack
042 {
043 // I didn't use ThreadLocal to release contexts explicitly.
044 // It seems like JDK 1.5 supports explicit release by introducing
045 // <tt>ThreadLocal.remove()</tt>, but we're still targetting 1.4.
046 private static final Map<Thread, InvocationStack> stacks =
047 Collections.synchronizedMap( new IdentityHashMap<Thread, InvocationStack>() );
048
049 private final Thread thread;
050 private final List<OperationContext> stack = new ArrayList<OperationContext>();
051
052
053 /**
054 * Returns the invocation stack of current thread.
055 */
056 public static InvocationStack getInstance()
057 {
058 Thread currentThread = Thread.currentThread();
059 InvocationStack ctx;
060 ctx = stacks.get( currentThread );
061
062 if ( ctx == null )
063 {
064 ctx = new InvocationStack( currentThread );
065 }
066
067 return ctx;
068 }
069
070
071 private InvocationStack( Thread currentThread )
072 {
073 thread = currentThread;
074 stacks.put( currentThread, this );
075 }
076
077
078 /**
079 * Returns an array of {@link Invocation}s. 0th element is the
080 * latest invocation.
081 */
082 public OperationContext[] toArray()
083 {
084 OperationContext[] result = new OperationContext[stack.size()];
085 result = stack.toArray( result );
086 return result;
087 }
088
089
090 /**
091 * Returns the latest invocation.
092 */
093 public OperationContext peek()
094 {
095 return stack.get( 0 );
096 }
097
098
099 /**
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 }