| /* |
| * Copyright (c) 1997, 2001, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package sun.rmi.log; |
| |
| import java.io.*; |
| import sun.rmi.server.MarshalOutputStream; |
| import sun.rmi.server.MarshalInputStream; |
| |
| /** |
| * A LogHandler represents snapshots and update records as serializable |
| * objects. |
| * |
| * This implementation does not know how to create an initial snaphot or |
| * apply an update to a snapshot. The client must specifiy these methods |
| * via a subclass. |
| * |
| * @see ReliableLog |
| * |
| * @author Ann Wollrath |
| */ |
| public abstract |
| class LogHandler { |
| |
| /** |
| * Creates a LogHandler for a ReliableLog. |
| */ |
| public LogHandler() {} |
| |
| /** |
| * Creates and returns the initial state of data structure that needs |
| * to be stably stored. This method is called when a ReliableLog is |
| * created. |
| * @return the initial state |
| * @exception Exception can raise any exception |
| */ |
| public abstract |
| Object initialSnapshot() throws Exception; |
| |
| /** |
| * Writes the snapshot object to a stream. This callback is |
| * invoked when the client calls the snaphot method of ReliableLog. |
| * @param out the output stream |
| * @param value the snapshot |
| * @exception Exception can raise any exception |
| */ |
| public |
| void snapshot(OutputStream out, Object value) throws Exception { |
| MarshalOutputStream s = new MarshalOutputStream(out); |
| s.writeObject(value); |
| s.flush(); |
| } |
| |
| /** |
| * Read the snapshot object from a stream and returns the snapshot. |
| * This callback is invoked when the client calls the recover method |
| * of ReliableLog. |
| * @param in the input stream |
| * @return the state (snapshot) |
| * @exception Exception can raise any exception |
| */ |
| |
| public |
| Object recover(InputStream in) throws Exception { |
| MarshalInputStream s = new MarshalInputStream(in); |
| return s.readObject(); |
| } |
| |
| /** |
| * Writes the representation (a serializable object) of an update |
| * to a stream. This callback is invoked when the client calls the |
| * update method of ReliableLog. |
| * @param out the output stream |
| * @param value the snapshot |
| * @exception Exception can raise any exception |
| */ |
| public |
| void writeUpdate(LogOutputStream out, Object value) throws Exception { |
| |
| MarshalOutputStream s = new MarshalOutputStream(out); |
| s.writeObject(value); |
| s.flush(); |
| } |
| |
| /** |
| * Reads a stably logged update (a serializable object) from a |
| * stream. This callback is invoked during recovery, once for |
| * every record in the log. After reading the update, this method |
| * invokes the applyUpdate (abstract) method in order to obtain |
| * the new snapshot value. It then returns the new snapshot. |
| * |
| * @param in the input stream |
| * @param state the current state |
| * @return the new state |
| * @exception Exception can raise any exception |
| */ |
| public |
| Object readUpdate(LogInputStream in, Object state) throws Exception { |
| MarshalInputStream s = new MarshalInputStream(in); |
| return applyUpdate(s.readObject(), state); |
| } |
| |
| /** |
| * Reads a stably logged update (a serializable object) from a stream. |
| * This callback is invoked during recovery, once for every record in the |
| * log. After reading the update, this method is invoked in order to |
| * obtain the new snapshot value. The method should apply the update |
| * object to the current state <code>state</code> and return the new |
| * state (the new snapshot value). |
| * @param update the update object |
| * @param state the current state |
| * @return the new state |
| * @exception Exception can raise any exception |
| */ |
| public abstract |
| Object applyUpdate(Object update, Object state) throws Exception; |
| |
| } |