CachedResource


1   // ========================================================================
2   // $Id: CachedResource.java,v 1.6 2004/05/09 20:32:49 gregwilkins Exp $
3   // Copyright 1996-2004 Mort Bay Consulting Pty. Ltd.
4   // ------------------------------------------------------------------------
5   // Licensed under the Apache License, Version 2.0 (the "License");
6   // you may not use this file except in compliance with the License.
7   // You may obtain a copy of the License at 
8   // http://www.apache.org/licenses/LICENSE-2.0
9   // Unless required by applicable law or agreed to in writing, software
10  // distributed under the License is distributed on an "AS IS" BASIS,
11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  // See the License for the specific language governing permissions and
13  // limitations under the License.
14  // ========================================================================
15  package org.mortbay.util;
16  
17  import java.io.ByteArrayInputStream  ;
18  import java.io.File  ;
19  import java.io.IOException  ;
20  import java.io.InputStream  ;
21  import java.io.OutputStream  ;
22  import java.net.MalformedURLException  ;
23  import java.net.URL  ;
24  
25  /* ------------------------------------------------------------ */
26  /** Cached resource class.
27   *
28   * This resource caches in memory the contents of another resource.
29   * The update() method must be called to check if the real resource has
30   * been modified.
31   * @version $Id: CachedResource.java,v 1.6 2004/05/09 20:32:49 gregwilkins Exp $
32   * @author Greg Wilkins (gregw)
33   */
34  
35  public class CachedResource extends Resource
36  {
37      Resource _resource;
38      long _lastModified;
39      byte[] _buf ;
40      String  [] _list;
41      
42      /* ------------------------------------------------------------ */
43      CachedResource(Resource resource)
44          throws IOException  
45      {
46          _resource=resource;
47          update();
48      }
49  
50      /* ------------------------------------------------------------ */
51      public synchronized boolean isUptoDate()
52          throws IOException  
53      {
54          return _resource!=null && _resource.exists() &&
55              _resource.lastModified()==_lastModified;
56      }
57      
58      /* ------------------------------------------------------------ */
59      public synchronized boolean update()
60          throws IOException  
61      {
62          if (_resource!=null && !_resource.exists())
63          {
64              clear();
65              return true;
66          }
67          
68          long lm=_resource.lastModified();
69          
70          if (lm==_lastModified && (_buf!=null || _list!=null))
71              return false;
72          _lastModified=lm;
73          
74          if (_resource.isDirectory())
75              _list=_resource.list();
76  
77          if (_list==null)
78          {
79              int l=(int)_resource.length();
80              if (l<0)
81                  l=1024;
82              ByteArrayOutputStream2 bout = new ByteArrayOutputStream2(l);
83              InputStream   in = _resource.getInputStream();
84              try{IO.copy(in,bout);} finally {in.close();}
85              _buf=bout.getBuf();
86              if (_buf.length!=l)
87                  _buf=bout.toByteArray();
88          }
89          return true;
90      }
91      
92      /* ------------------------------------------------------------ */
93      public synchronized void clear()
94      {
95          _buf=null;
96          _list=null;
97      }
98  
99      /* ------------------------------------------------------------ */
100     /** Release any resources held by the resource.
101      */
102     public void release()
103     {
104         clear();
105         _resource.release();
106     }
107 
108     /* ------------------------------------------------------------ */
109     /**
110      * Returns true if the respresened resource exists.
111      */
112     public synchronized boolean exists()
113     {
114         return _buf!=null || _list!=null;
115     }
116 
117     /* ------------------------------------------------------------ */
118     public boolean isDirectory()
119     {
120         return _list!=null;
121     }
122 
123 
124     /* ------------------------------------------------------------ */
125     public long lastModified()
126     {
127         return _lastModified;
128     }
129 
130     /* ------------------------------------------------------------ */
131     public long length()
132     {
133         if (_buf!=null)
134             return _buf.length;
135         return -1;
136     }
137 
138     /* ------------------------------------------------------------ */
139     public URL   getURL()
140     {
141         return _resource.getURL();
142     }
143 
144     /* ------------------------------------------------------------ */
145     public File   getFile()
146         throws IOException  
147     {
148         return _resource.getFile();
149     }
150 
151     /* ------------------------------------------------------------ */
152     /**
153      * Returns the name of the resource
154      */
155     public String   getName()
156     {
157         return _resource.getName();
158     }
159 
160     /* ------------------------------------------------------------ */
161     /**
162      * Returns an input stream to the resource
163      */
164     public InputStream   getInputStream()
165         throws IOException  
166     {
167         if (_buf!=null)
168             return new ByteArrayInputStream  (_buf);
169         return _resource.getInputStream();
170     }
171 
172 
173     /* ------------------------------------------------------------ */
174     /**
175      * Returns an output stream to the resource
176      */
177     public OutputStream   getOutputStream()
178         throws java.io.IOException  , SecurityException  
179     {
180         return _resource.getOutputStream();
181     }
182 
183     /* ------------------------------------------------------------ */
184     /**
185      * Deletes the given resource
186      */
187     public synchronized boolean delete()
188         throws SecurityException  
189     {
190         if (_resource.delete())
191         {
192             clear();
193             return true;
194         }
195         return false;
196     }
197 
198     /* ------------------------------------------------------------ */
199     /**
200      * Rename the given resource
201      */
202     public synchronized boolean renameTo( Resource dest)
203         throws SecurityException  
204     {
205         if (_resource.renameTo(dest))
206         {
207             clear();
208             return true;
209         }
210         return false;
211     }
212 
213     /* ------------------------------------------------------------ */
214     /**
215      * Returns a list of resource names contained in the given resource
216      */
217     public String  [] list()
218     {
219         return _list;
220     }
221 
222     /* ------------------------------------------------------------ */
223     /**
224      * Returns the resource contained inside the current resource with the
225      * given name
226      */
227     public Resource addPath(String   path)
228         throws IOException  ,MalformedURLException  
229     {
230         return _resource.addPath(path);
231     }
232 
233     /* ------------------------------------------------------------ */
234     public String   toString()
235     {
236         return _resource.toString();
237     }
238 
239     /* ------------------------------------------------------------ */
240     public int hashCode()
241     {
242         return _resource.hashCode();
243     }
244     
245     /* ------------------------------------------------------------ */
246     public boolean equals( Object   o)
247     {
248         return _resource.equals(o);
249     }
250 
251     /* ------------------------------------------------------------ */
252     public void writeTo(OutputStream   os, long startByte, long count) 
253         throws IOException  
254     {
255         if (count<0)
256             count=_buf.length-startByte;
257         if (_buf!=null)
258             os.write(_buf, (int) startByte, (int) count);
259     }
260     
261     /* ------------------------------------------------------------ */
262     public byte[] getCachedData()
263     {
264         return _buf;
265     }
266     
267     /* ------------------------------------------------------------ */
268     public void setCachedData(byte[] buf)
269     {
270         _buf = buf;
271     }
272 
273     
274 }
275
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags