1 /*
2 * Copyright 2007-2008 The Kuali Foundation
3 *
4 * Licensed under the Educational Community License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.opensource.org/licenses/ecl2.php
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package org.kuali.rice.core.util;
17
18 import java.lang.ref.SoftReference;
19
20 /**
21 * An extension to SoftReference that stores an expiration time for the
22 * value stored in the SoftReference. If no expiration time is passed in
23 * the value will never be cached.
24 */
25 public class MaxAgeSoftReference<T> extends SoftReference<T> {
26
27 private long expires;
28
29 public MaxAgeSoftReference(long expires, T referent) {
30 super(referent);
31 this.expires = System.currentTimeMillis() + expires * 1000;
32 }
33
34 public boolean isValid() {
35 return System.currentTimeMillis() < expires;
36 }
37
38 public T get() {
39 return isValid() ? super.get() : null;
40 }
41
42 }