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1 package com.vipan.util;
2
3 import java.util.*;
4 import org.apache.log4j.*;
5 import org.apache.commons.collections.map.LRUMap;
6 import org.apache.commons.collections.MapIterator;
7
8
9
18 public class ExpiringCache {
19
20 static Category logger = Category.getInstance(ExpiringCache.class);
21
22 public static final long DEFAULT_TIME_TO_LIVE = 10 * 60 * 1000;
23 public static final long DEFAULT_ACCESS_TIMEOUT = 5 * 60 * 1000;
24 public static final long DEFAULT_TIMER_INTERVAL = 2 * 60 * 1000;
25
26 long ttl = DEFAULT_TIME_TO_LIVE;
27 long ato = DEFAULT_ACCESS_TIMEOUT;
28 long tiv = DEFAULT_TIMER_INTERVAL;
29
30 LRUMap cacheMap;
31 Timer cacheManager;
32
33
34 protected void finalize() throws Throwable  {
35 if (cacheManager != null) cacheManager.cancel();
36 }
37
38 public ExpiringCache() {
39 cacheMap = new LRUMap();
40 initialize();
41 }
42
43 public ExpiringCache(long timeToLive, long accessTimeout,
45 int maximumCachedQuantity, long timerInterval
46 ) {
47 ttl = timeToLive;
48 ato = accessTimeout;
49 cacheMap = new LRUMap(maximumCachedQuantity);
50 tiv = timerInterval;
51 initialize();
52 }
53
54
55 public void setTimeToLive(long milliSecs) {
56 ttl = milliSecs;
57 initialize();
58 }
59
60
61
62 public void setAccessTimeout(long milliSecs) {
63 ato = milliSecs;
64 initialize();
65 }
66
67
68
69 public void setCleaningInterval(long milliSecs) {
70 tiv = milliSecs;
71 initialize();
72 }
73
74
75 public void initialize() {
76 if (logger.isDebugEnabled()) logger.debug("initialize() started");
77 if (cacheManager != null) cacheManager.cancel();
78 cacheManager = new Timer(true);
79 cacheManager.schedule(
80 new TimerTask() {
81 public void run() {
82 NDC.push("TimerTask");
83 long now = System.currentTimeMillis();
84 try {
85 MapIterator itr = cacheMap.mapIterator();
86 while (itr.hasNext()) {
87 Object key = itr.next();
88 CachedObject cobj = (CachedObject) itr.getValue();
89 if (cobj == null || cobj.hasExpired(now)) {
90 if (logger.isDebugEnabled()) logger.debug(
91 "Removing " + key + ": Idle time=" +
92 (now - cobj.timeAccessedLast) + "; Stale time:" +
93 (now - cobj.timeCached));
94 itr.remove();
95 Thread.yield();
96 }
97 }
98 }
99 catch (ConcurrentModificationException cme) {
100
104 if (logger.isDebugEnabled()) logger.debug(
105 "Ignorable ConcurrentModificationException");
106 }
107 NDC.remove();
108 }
109 },
110 0,
111 tiv
112 );
113 }
114
115
116
117
118 public int howManyObjects() {
119 return cacheMap.size();
120 }
121
122
123 public void clear() {
124 cacheMap.clear();
125 }
126
127
135 public Object admit(Object key, Object dataToCache) {
136
139 CachedObject cobj = (CachedObject) cacheMap.get(key);
140 if (cobj == null) {
141 cacheMap.put(key, new CachedObject(dataToCache));
142 return null;
143 }
144 else {
145 Object obj = cobj.getCachedData(key);
146 if (obj == null) {
147 if (dataToCache == null) {
148 cobj.timeCached = cobj.timeAccessedLast = System.currentTimeMillis();
151 return null;
152 }
153 else {
154 cacheMap.put(key, new CachedObject(dataToCache));
155 return null;
156 }
157 }
158 else if (obj.equals(dataToCache)) {
159 cobj.timeCached = cobj.timeAccessedLast = System.currentTimeMillis();
162 return null;
163 }
164 else {
165 cacheMap.put(key, new CachedObject(dataToCache));
166 return obj;
167 }
168 }
169 }
170
171
172
173 public Object admit(Object key, Object dataToCache, long objectTimeToLive, long objectIdleTimeout) {
174
177 CachedObject cobj = (CachedObject) cacheMap.get(key);
178 if (cobj == null) {
179 cacheMap.put(key, new CachedObject(dataToCache, objectTimeToLive, objectIdleTimeout));
180 return null;
181 }
182 else {
183 Object obj = cobj.getCachedData(key);
184 if (obj == null) {
185 if (dataToCache == null) {
186 cobj.timeCached = cobj.timeAccessedLast = System.currentTimeMillis();
189 cobj.objectTTL = objectTimeToLive;
190 cobj.objectIdleTimeout = objectIdleTimeout;
191 cobj.userTimeouts = true;
192 return null;
193 }
194 else {
195 cacheMap.put(key, new CachedObject(dataToCache, objectTimeToLive, objectIdleTimeout));
196 return null;
197 }
198 }
199 else if (obj.equals(dataToCache)) {
200 cobj.timeCached = cobj.timeAccessedLast = System.currentTimeMillis();
203 cobj.objectTTL = objectTimeToLive;
204 cobj.objectIdleTimeout = objectIdleTimeout;
205 cobj.userTimeouts = true;
206 return null;
207 }
208 else {
209 cacheMap.put(key, new CachedObject(dataToCache, objectTimeToLive, objectIdleTimeout));
210 return obj;
211 }
212 }
213 }
214
215
216
217 public Object recover(Object key) {
218 CachedObject cobj = (CachedObject) cacheMap.get(key);
219 if (cobj == null) return null;
220 else return cobj.getCachedData(key);
221 }
222
223
224 public void discard(Object key) {
225 cacheMap.remove(key);
226 }
227
228
229 public long whenCached(Object key) {
230 CachedObject cobj = (CachedObject) cacheMap.get(key);
231 if (cobj == null) return 0;
232 return cobj.timeCached;
233 }
234
235
236 public long whenLastAccessed(Object key) {
237 CachedObject cobj = (CachedObject) cacheMap.get(key);
238 if (cobj == null) return 0;
239 return cobj.timeAccessedLast;
240 }
241
242
243 public int howManyTimesAccessed(Object key) {
244 CachedObject cobj = (CachedObject) cacheMap.get(key);
245 if (cobj == null) return 0;
246 return cobj.numberOfAccesses;
247 }
248
249
250
254 protected class CachedObject {
255 Object cachedData;
256 long timeCached;
257 long timeAccessedLast;
258 int numberOfAccesses;
259 long objectTTL;
260 long objectIdleTimeout;
261 boolean userTimeouts;
262
263
264 CachedObject(Object cachedData) {
265 long now = System.currentTimeMillis();
266 this.cachedData = cachedData;
267 timeCached = now;
268 timeAccessedLast = now;
269 ++numberOfAccesses;
270 }
271
272 CachedObject(Object cachedData, long timeToLive, long idleTimeout) {
273 long now = System.currentTimeMillis();
274 this.cachedData = cachedData;
275 objectTTL = timeToLive;
276 objectIdleTimeout = idleTimeout;
277 userTimeouts = true;
278 timeCached = now;
279 timeAccessedLast = now;
280 ++numberOfAccesses;
281 }
282
283
284 Object getCachedData(Object key) {
285 long now = System.currentTimeMillis();
286 if (hasExpired(now)) {
287 cachedData = null;
288 cacheMap.remove(key);
289 return null;
290 }
291 timeAccessedLast = now;
292 ++numberOfAccesses;
293 return cachedData;
294 }
295
296 boolean hasExpired(long now) {
297 long usedTTL = userTimeouts?objectTTL:ttl;
298 long usedATO = userTimeouts?objectIdleTimeout:ato;
299
300 if (now > timeAccessedLast + usedATO ||
301 now > timeCached + usedTTL
302 ) {
303 return true;
304 }
305 else return false;
306 }
307
308
309 }
310
311
312
313 }
315
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