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Java > Open Source Codes > com > opensymphony > oscache > web > filter > ExpiresRefreshPolicy


1 /*
2  * Copyright (c) 2002-2003 by OpenSymphony
3  * All rights reserved.
4  */
5 package com.opensymphony.oscache.web.filter;
6
7 import com.opensymphony.oscache.base.CacheEntry;
8 import com.opensymphony.oscache.base.EntryRefreshPolicy;
9 import com.opensymphony.oscache.base.NeedsRefreshException;
10
11 /**
12  * Checks if a cache filter entry has expired.
13  * This is useful when expires header are used in the response.
14  *
15  * @version $Revision: 1.1 $
16  * @author <a HREF="mailto:ltorunski@t-online.de">Lars Torunski</a>
17  */
18 public class ExpiresRefreshPolicy implements EntryRefreshPolicy {
19     
20     /** the refresh period (in milliseconds) of a certain cache filter*/
21     private long refreshPeriod;
22
23     /**
24      * Constructor ExpiresRefreshPolicy.
25      *
26      * @param refreshPeriod the refresh period in seconds
27      */
28     public ExpiresRefreshPolicy(int refreshPeriod) {
29         this.refreshPeriod = refreshPeriod * 1000L;
30     }
31     
32     /**
33      * Indicates whether the supplied <code>CacheEntry</code> needs to be refreshed.
34      * This will be called when retrieving an entry from the cache - if this method
35      * returns <code>true</code> then a <code>NeedsRefreshException</code> will be
36      * thrown.
37      *
38      * @param entry The cache entry which is ignored.
39      * @return <code>true</code> if the content needs refreshing, <code>false</code> otherwise.
40      *
41      * @see NeedsRefreshException
42      * @see CacheEntry
43      */
44     public boolean needsRefresh(CacheEntry entry) {
45         
46         long currentTimeMillis = System.currentTimeMillis();
47         
48         if ((refreshPeriod >= 0) && (currentTimeMillis >= (entry.getLastUpdate() + refreshPeriod))) {
49             return true;
50         } else if (entry.getContent() instanceof ResponseContent) {
51             ResponseContent responseContent = (ResponseContent) entry.getContent();
52             return currentTimeMillis >= responseContent.getExpires();
53         } else {
54             return false;
55         }
56         
57     }
58     
59 }
60
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