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| 1 | /* | ||
| 2 | * Copyright (c) 1997, 2001, 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 | |||
| 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 | } | ||