1 /*
2 * This file is part of Waarp Project (named also Waarp or GG).
3 *
4 * Copyright (c) 2019, Waarp SAS, and individual contributors by the @author
5 * tags. See the COPYRIGHT.txt in the distribution for a full listing of
6 * individual contributors.
7 *
8 * All Waarp Project is free software: you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation, either version 3 of the License, or (at your
11 * option) any later version.
12 *
13 * Waarp is distributed in the hope that it will be useful, but WITHOUT ANY
14 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
15 * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License along with
18 * Waarp . If not, see <http://www.gnu.org/licenses/>.
19 */
20 package org.waarp.common.lru;
21
22 import java.lang.ref.SoftReference;
23
24 /**
25 * Cache entry which uses SoftReference to store value
26 *
27 * @author Damian Momot
28 */
29 class SoftReferenceCacheEntry<V> implements InterfaceLruCacheEntry<V> {
30
31 private final SoftReference<V> valueReference;
32
33 private long expirationTime;
34
35 /**
36 * Creates LruCacheEntry with desired ttl
37 *
38 * @param value
39 * @param ttl time to live in milliseconds
40 *
41 * @throws IllegalArgumentException if ttl is not positive
42 */
43 SoftReferenceCacheEntry(final V value, final long ttl) {
44 if (ttl <= 0) {
45 throw new IllegalArgumentException("ttl must be positive");
46 }
47
48 valueReference = new SoftReference<V>(value);
49 expirationTime = System.currentTimeMillis() + ttl;
50 }
51
52 /**
53 * Returns value if entry is valid, null otherwise.
54 * <p>
55 * Entry is invalid if SoftReference is cleared or entry has expired
56 *
57 * @return value if entry is valid
58 */
59 @Override
60 public final V getValue() {
61 V value = null;
62
63 // check expiration time
64 if (System.currentTimeMillis() <= expirationTime) {
65 value = valueReference.get();
66 }
67
68 return value;
69 }
70
71 @Override
72 public final boolean isStillValid(final long timeRef) {
73 return timeRef <= expirationTime;
74 }
75
76 @Override
77 public final boolean resetTime(final long ttl) {
78 expirationTime = System.currentTimeMillis() + ttl;
79 return true;
80 }
81 }