VirtualFileCache


1   /*
2    * The contents of this file are subject to the 
3    * Mozilla Public License Version 1.1 (the "License"); 
4    * you may not use this file except in compliance with the License. 
5    * You may obtain a copy of the License at http://www.mozilla.org/MPL/
6    *
7    * Software distributed under the License is distributed on an "AS IS"
8    * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. 
9    * See the License for the specific language governing rights and 
10   * limitations under the License.
11   *
12   * The Initial Developer of the Original Code is Simulacra Media Ltd.
13   * Portions created by Simulacra Media Ltd are Copyright (C) Simulacra Media Ltd, 2004.
14   *
15   * All Rights Reserved.
16   *
17   * Contributor(s):
18   */
19  package org.openharmonise.vfs;
20  
21  import java.util.ArrayList  ;
22  import java.util.Date  ;
23  import java.util.HashMap  ;
24  import java.util.List  ;
25  
26  /**
27   * Generic cache for VirtualFileObjects. The default timeout for these objects
28   * is 5 minutes, this can be overridden.
29   * 
30   * @author Matthew Large
31   * @version $Revision: 1.1 $
32   *
33   */
34  public class VirtualFileCache {
35  
36      /**
37       * Map of path to {@link TimestampedObject} objects.
38       */
39      private HashMap   m_files = new HashMap  (71);
40      
41      /**
42       * Timeout value for virtual files in the cache in milliseconds.
43       */
44      private int m_nTimeout = 60000 /*1 minute in milliseconds*/ * 20 /*minutes*/;
45  
46      /**
47       * Constructs a VirtualFileCache with a specific timeout, overriding the default
48       * 5 minute timeout.
49       * 
50       * @param nTimeout Sets the cache's timeout value in milliseconds. (60000=1 minute)
51       */
52      public VirtualFileCache(int nTimeout) {
53          super();
54          this.m_nTimeout=nTimeout;
55      }
56      
57      public VirtualFileCache() {
58          super();
59      }
60  
61      /**
62       * Checks if the cache contains a specific VirtualFile as indexed by path.
63       * 
64       * @param sFullpath The full path of the VirtualFile to be checked
65       * @return true if the cache contains the VirtualFile. If the VirtualFile has timed out it will be removed from the cache and False will be returned
66       */
67      public synchronized boolean hasFile(String   sFullpath) {
68        boolean bRetn = false;
69        if(sFullpath!=null && sFullpath.endsWith("/")) {
70          sFullpath = sFullpath.substring(0, sFullpath.length()-1);
71        }
72      
73        if( sFullpath!=null && m_files.containsKey(sFullpath.trim()) && m_files.get(sFullpath.trim())!=null ) {
74            if( !((TimestampedObject)m_files.get(sFullpath.trim())).isTimedOut(this.m_nTimeout)) {
75                bRetn=true;
76            } else {
77                this.removeFile(sFullpath.trim());
78            }
79        }
80        if(!bRetn) {
81          
82        }
83        
84        return bRetn;
85      }
86    
87      /**
88       * Gets a List object containing all the path Strings in the cache.
89       * 
90       * @return List of path Strings
91       */
92      public List   getPaths() {
93        List   vPaths = new ArrayList  (this.m_files.keySet());
94      
95        return vPaths;
96      }
97  
98      /**
99       * Adds a VirtualFile to the cache, if a VirtualFile with the path is already in the cache it will be overwritten with this one.
100      * 
101      * @param vfFile VirtualFile to be added
102      */
103     public synchronized void addFile(VirtualFile vfFile) {
104       TimestampedObject tsObj = new TimestampedObject(vfFile);
105       if(m_files.keySet().contains(vfFile.getFullPath().trim())) {
106         if( !((VirtualFile)((TimestampedObject)m_files.get(vfFile.getFullPath().trim())).getObject()).isChanged() ) {
107             m_files.put(vfFile.getFullPath().trim(), tsObj);
108         }
109       } else {
110         m_files.put(vfFile.getFullPath().trim(), tsObj);
111       }
112     }
113 
114     /**
115      * Gets a VirtualFile from the cache as specified by the path.
116      * 
117      * @param sFullpath Path of the VirtualFile to be returned
118      * @return Requested VirtualFile or null if path is not found in cache
119      */
120     public VirtualFile getFile(String   sFullpath) {
121       VirtualFile vfRetn = null;
122       if(sFullpath.endsWith("/")) {
123         sFullpath = sFullpath.substring(0, sFullpath.length()-1);
124       }
125     
126       TimestampedObject tsObj = (TimestampedObject)m_files.get(sFullpath.trim());
127       if( tsObj!=null ) {
128         
129             if( !((VirtualFile)tsObj.getObject()).getFullPath().equalsIgnoreCase(sFullpath)) {
130             }
131         
132           long currTime = new Date  ().getTime();
133           if( !tsObj.isTimedOut(this.m_nTimeout) ) {
134               vfRetn = (VirtualFile)tsObj.getObject();
135               tsObj.resetTimestamp();
136           } else {
137               this.removeFile(sFullpath);
138           } 
139       }
140 
141       return vfRetn;
142     }
143 
144 
145     /**
146      * Removes a specific VirtualFile from the cache.
147      * 
148      * @param sFullpath Path of VirtualFile to be removed
149      * @return previous value associated with specified key, or null if there was no mapping for key
150      */
151     public VirtualFile removeFile(String   sFullpath) {
152       return (VirtualFile)((TimestampedObject)m_files.remove(sFullpath)).getObject();
153     }
154 
155         /**
156        * Wraps an object with a timestamp
157        * 
158        * @author Matthew Large
159        */
160       private class TimestampedObject {
161           private Object   m_object;
162           private Long   m_timestamp;
163 
164           /**
165          * Wraps the supplied object and gives it a timestamp of the current system time.
166          * 
167          * @param obj Object to be timestamped
168          */
169         public TimestampedObject(Object   obj) {
170               this(obj, new Long  (new Date  ().getTime()));
171           }
172 
173           /**
174          * Wraps the supplied object and gives it the specified timestamp.
175          * 
176          * @param obj Object to be timestamped
177          * @param timestamp Timestamp to give to the object
178          */
179         public TimestampedObject(Object   obj, Long   timestamp) {
180               m_timestamp = timestamp;
181               m_object = obj;
182           }
183         
184           /**
185          * Checks a timeout value
186          * 
187          * @param nTimeout
188          * @return True if the object is timed out
189          */
190         private boolean isTimedOut(int nTimeout) {
191           long currTime = new Date  ().getTime();
192           return (  !((VirtualFile)this.getObject()).hasVirtualFileListeners() && !((VirtualFile)this.getObject()).isChanged() && (currTime-getTimestamp().longValue())>nTimeout);
193       }
194 
195           /**
196          * Gets the object
197          * 
198          * @return Object that is wrapped by this Timestampedobject
199          */
200         public Object   getObject() {
201               return m_object;
202           }
203 
204           /**
205          * Gets the current timestamp value
206          * 
207          * @return Timestamp in milliseconds
208          */
209         public Long   getTimestamp() {
210               return m_timestamp;
211           }
212         
213           /**
214          *  Resets the timestamp value to the current system time
215          */
216         public void resetTimestamp() {
217               m_timestamp=new Long  (new Date  ().getTime());
218           }
219 
220           /* (non-Javadoc)
221          * @see java.lang.Object#equals(java.lang.Object)
222          */
223         public boolean equals(Object   obj) {
224               TimestampedObject to = (TimestampedObject) obj;
225 
226               boolean bReturn = m_object.equals(to.getObject());
227 
228               return bReturn;
229           }
230 
231           /* (non-Javadoc)
232          * @see java.lang.Object#toString()
233          */
234         public String   toString() {
235               return "(" + m_object.hashCode() + "," + m_timestamp + ")";
236           }
237       }
238 
239 }
240
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