1 /*
2 * Copyright (c) 2003, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package sun.management.snmp.util;
26
27 import com.sun.jmx.snmp.SnmpOid;
28
29 import java.io.Serializable;
30
31 import java.util.Comparator;
32 import java.util.Arrays;
33 import java.util.TreeMap;
34 import java.util.List;
35 import java.util.Iterator;
36
37 import java.lang.ref.WeakReference;
38
39 /**
40 * This abstract class implements a weak cache for a table whose data
41 * is obtained from a {@link List}.
42 *
43 * <p><b>NOTE: This class is not synchronized, subclasses must implement
44 * the appropriate synchronization whwn needed.</b></p>
45 **/
46 @SuppressWarnings("serial") // JDK implementation class
47 public abstract class SnmpListTableCache extends SnmpTableCache {
48
49
50 /**
51 * The index of the entry corresponding to the given <var>item</var>.
52 * <br>This method is called by {@link #updateCachedDatas(Object,List)}.
53 * The given <var>item</var> is expected to be always associated with
54 * the same index.
55 * @param context The context passed to
56 * {@link #updateCachedDatas(Object,List)}.
57 * @param rawDatas Raw table datas passed to
58 * {@link #updateCachedDatas(Object,List)}.
59 * @param rank Rank of the given <var>item</var> in the
60 * <var>rawDatas</var> list iterator.
61 * @param item The raw data object for which an index must be determined.
62 **/
63 protected abstract SnmpOid getIndex(Object context, List<?> rawDatas,
64 int rank, Object item);
65
66 /**
67 * The data for the entry corresponding to the given <var>item</var>.
68 * <br>This method is called by {@link #updateCachedDatas(Object,List)}.
69 * @param context The context passed to
70 * {@link #updateCachedDatas(Object,List)}.
71 * @param rawDatas Raw table datas passed to
72 * {@link #updateCachedDatas(Object,List)}.
73 * @param rank Rank of the given <var>item</var> in the
74 * <var>rawDatas</var> list iterator.
75 * @param item The raw data object from which the entry data must be
76 * extracted.
77 * @return By default <var>item</var> is returned.
78 **/
79 protected Object getData(Object context, List<?> rawDatas,
80 int rank, Object item) {
81 return item;
82 }
83
84 /**
85 * Recompute cached data.
86 * @param context A context object, valid during the duration of
87 * of the call to this method, and that will be passed to
88 * {@link #getIndex} and {@link #getData}. <br>
89 * This method is intended to be called by
90 * {@link #updateCachedDatas(Object)}. It is assumed that
91 * the context is be allocated by before this method is called,
92 * and released just after this method has returned.<br>
93 * This class does not use the context object: it is a simple
94 * hook for subclassed.
95 * @param rawDatas The table datas from which the cached data will be
96 * computed.
97 * @return the computed cached data.
98 **/
99 protected SnmpCachedData updateCachedDatas(Object context, List<?> rawDatas) {
100 final int size = ((rawDatas == null)?0:rawDatas.size());
101 if (size == 0) return null;
102
103 final long time = System.currentTimeMillis();
104 final Iterator<?> it = rawDatas.iterator();
105 final TreeMap<SnmpOid, Object> map =
106 new TreeMap<>(SnmpCachedData.oidComparator);
107 for (int rank=0; it.hasNext() ; rank++) {
108 final Object item = it.next();
109 final SnmpOid index = getIndex(context, rawDatas, rank, item);
110 final Object data = getData(context, rawDatas, rank, item);
111 if (index == null) continue;
112 map.put(index,data);
113 }
114
115 return new SnmpCachedData(time,map);
116 }
117
118 }