001: package org.apache.turbine.services.cache;
002:
003: /*
004: * Licensed to the Apache Software Foundation (ASF) under one
005: * or more contributor license agreements. See the NOTICE file
006: * distributed with this work for additional information
007: * regarding copyright ownership. The ASF licenses this file
008: * to you under the Apache License, Version 2.0 (the
009: * "License"); you may not use this file except in compliance
010: * with the License. You may obtain a copy of the License at
011: *
012: * http://www.apache.org/licenses/LICENSE-2.0
013: *
014: * Unless required by applicable law or agreed to in writing,
015: * software distributed under the License is distributed on an
016: * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017: * KIND, either express or implied. See the License for the
018: * specific language governing permissions and limitations
019: * under the License.
020: */
021:
022: /**
023: * The idea of the RefreshableCachedObject is that, rather than
024: * removing items from the cache when they become stale, we'll tell them to
025: * refresh themselves instead. That way they'll always be in the
026: * cache, and the code to refresh them will be run by the background
027: * thread rather than by a user request thread. You can also set a TTL (Time
028: * To Live) for the object. This way, if the object hasn't been touched
029: * for the TTL period, then it will be removed from the cache.
030: *
031: * This extends CachedObject and provides a method for refreshing the
032: * cached object, and resetting its expire time.
033: *
034: * @author <a href="mailto:nissim@nksystems.com">Nissim Karpenstein</a>
035: * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
036: * @version $Id: RefreshableCachedObject.java 534527 2007-05-02 16:10:59Z tv $
037: */
038: public class RefreshableCachedObject extends CachedObject {
039:
040: /** Serial Version UID */
041: private static final long serialVersionUID = 727229797378897180L;
042:
043: /**
044: * How long to wait before removing an untouched object from the cache.
045: * Negative numbers mean never remove (the default).
046: */
047: private long timeToLive = -1;
048:
049: /**
050: * The last time the Object was accessed from the cache.
051: */
052: private long lastAccess;
053:
054: /**
055: * Constructor; sets the object to expire in the default time (30
056: * minutes).
057: *
058: * @param o The object you want to cache.
059: */
060: public RefreshableCachedObject(Refreshable o) {
061: super (o);
062: lastAccess = System.currentTimeMillis();
063: }
064:
065: /**
066: * Constructor.
067: *
068: * @param o The object to cache.
069: * @param expires How long before the object expires, in ms,
070: * e.g. 1000 = 1 second.
071: */
072: public RefreshableCachedObject(Refreshable o, long expires) {
073: super (o, expires);
074: lastAccess = System.currentTimeMillis();
075: }
076:
077: /**
078: * Sets the timeToLive value
079: *
080: * @param timeToLive the new Value in milliseconds
081: */
082: public synchronized void setTTL(long timeToLive) {
083: this .timeToLive = timeToLive;
084: }
085:
086: /**
087: * Gets the timeToLive value.
088: *
089: * @return The current timeToLive value (in milliseconds)
090: */
091: public synchronized long getTTL() {
092: return timeToLive;
093: }
094:
095: /**
096: * Sets the last acccess time to the current time.
097: */
098: public synchronized void touch() {
099: lastAccess = System.currentTimeMillis();
100: }
101:
102: /**
103: * Returns true if the object hasn't been touched
104: * in the previous TTL period.
105: */
106: public synchronized boolean isUntouched() {
107: if (timeToLive < 0)
108: return false;
109:
110: if (lastAccess + timeToLive < System.currentTimeMillis())
111: return true;
112: else
113: return false;
114: }
115:
116: /**
117: * Refresh the object and the created time.
118: */
119: public void refresh() {
120: Refreshable r = (Refreshable) getContents();
121: synchronized (this) {
122: created = System.currentTimeMillis();
123: r.refresh();
124: }
125: }
126: }
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