J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1997-2001 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package sun.rmi.log; |
| 27 | |
| 28 | import java.io.*; |
| 29 | import sun.rmi.server.MarshalOutputStream; |
| 30 | import sun.rmi.server.MarshalInputStream; |
| 31 | |
| 32 | /** |
| 33 | * A LogHandler represents snapshots and update records as serializable |
| 34 | * objects. |
| 35 | * |
| 36 | * This implementation does not know how to create an initial snaphot or |
| 37 | * apply an update to a snapshot. The client must specifiy these methods |
| 38 | * via a subclass. |
| 39 | * |
| 40 | * @see ReliableLog |
| 41 | * |
| 42 | * @author Ann Wollrath |
| 43 | */ |
| 44 | public abstract |
| 45 | class LogHandler { |
| 46 | |
| 47 | /** |
| 48 | * Creates a LogHandler for a ReliableLog. |
| 49 | */ |
| 50 | public LogHandler() {} |
| 51 | |
| 52 | /** |
| 53 | * Creates and returns the initial state of data structure that needs |
| 54 | * to be stably stored. This method is called when a ReliableLog is |
| 55 | * created. |
| 56 | * @return the initial state |
| 57 | * @exception Exception can raise any exception |
| 58 | */ |
| 59 | public abstract |
| 60 | Object initialSnapshot() throws Exception; |
| 61 | |
| 62 | /** |
| 63 | * Writes the snapshot object to a stream. This callback is |
| 64 | * invoked when the client calls the snaphot method of ReliableLog. |
| 65 | * @param out the output stream |
| 66 | * @param value the snapshot |
| 67 | * @exception Exception can raise any exception |
| 68 | */ |
| 69 | public |
| 70 | void snapshot(OutputStream out, Object value) throws Exception { |
| 71 | MarshalOutputStream s = new MarshalOutputStream(out); |
| 72 | s.writeObject(value); |
| 73 | s.flush(); |
| 74 | } |
| 75 | |
| 76 | /** |
| 77 | * Read the snapshot object from a stream and returns the snapshot. |
| 78 | * This callback is invoked when the client calls the recover method |
| 79 | * of ReliableLog. |
| 80 | * @param in the input stream |
| 81 | * @return the state (snapshot) |
| 82 | * @exception Exception can raise any exception |
| 83 | */ |
| 84 | |
| 85 | public |
| 86 | Object recover(InputStream in) throws Exception { |
| 87 | MarshalInputStream s = new MarshalInputStream(in); |
| 88 | return s.readObject(); |
| 89 | } |
| 90 | |
| 91 | /** |
| 92 | * Writes the representation (a serializable object) of an update |
| 93 | * to a stream. This callback is invoked when the client calls the |
| 94 | * update method of ReliableLog. |
| 95 | * @param out the output stream |
| 96 | * @param value the snapshot |
| 97 | * @exception Exception can raise any exception |
| 98 | */ |
| 99 | public |
| 100 | void writeUpdate(LogOutputStream out, Object value) throws Exception { |
| 101 | |
| 102 | MarshalOutputStream s = new MarshalOutputStream(out); |
| 103 | s.writeObject(value); |
| 104 | s.flush(); |
| 105 | } |
| 106 | |
| 107 | /** |
| 108 | * Reads a stably logged update (a serializable object) from a |
| 109 | * stream. This callback is invoked during recovery, once for |
| 110 | * every record in the log. After reading the update, this method |
| 111 | * invokes the applyUpdate (abstract) method in order to obtain |
| 112 | * the new snapshot value. It then returns the new snapshot. |
| 113 | * |
| 114 | * @param in the input stream |
| 115 | * @param state the current state |
| 116 | * @return the new state |
| 117 | * @exception Exception can raise any exception |
| 118 | */ |
| 119 | public |
| 120 | Object readUpdate(LogInputStream in, Object state) throws Exception { |
| 121 | MarshalInputStream s = new MarshalInputStream(in); |
| 122 | return applyUpdate(s.readObject(), state); |
| 123 | } |
| 124 | |
| 125 | /** |
| 126 | * Reads a stably logged update (a serializable object) from a stream. |
| 127 | * This callback is invoked during recovery, once for every record in the |
| 128 | * log. After reading the update, this method is invoked in order to |
| 129 | * obtain the new snapshot value. The method should apply the update |
| 130 | * object to the current state <code>state</code> and return the new |
| 131 | * state (the new snapshot value). |
| 132 | * @param update the update object |
| 133 | * @param state the current state |
| 134 | * @return the new state |
| 135 | * @exception Exception can raise any exception |
| 136 | */ |
| 137 | public abstract |
| 138 | Object applyUpdate(Object update, Object state) throws Exception; |
| 139 | |
| 140 | } |