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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 | +} | |