Mercurial > hg > blitz_condensed
diff src/org/prevayler/implementation/SnapshotPrevaylerImpl.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/org/prevayler/implementation/SnapshotPrevaylerImpl.java Sat Mar 21 11:00:06 2009 +0000 @@ -0,0 +1,261 @@ +/* + The copyright of all source code included in this Prevayler distribution is + held by Klaus Wuestefeld, except the files that specifically state otherwise. + All rights are reserved. "PREVAYLER" is a trademark of Klaus Wuestefeld. + + + BSD License: + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions are met: + + - Redistributions of source code must retain the above copyright notice, this + list of conditions and the following disclaimer. + + - Redistributions in binary form must reproduce the above copyright notice, + this list of conditions and the following disclaimer in the documentation + and/or other materials provided with the distribution. + + - Neither the name of Prevayler nor the names of its contributors may be used + to endorse or promote products derived from this software without specific + prior written permission. + + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE + LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + POSSIBILITY OF SUCH DAMAGE. +*/ + +package org.prevayler.implementation; + +import java.util.Date; +import java.io.*; + +import java.rmi.RMISecurityManager; + +import org.prevayler.*; + +/** Provides transparent persistence for business objects. +* This applies to any deterministic system implementing the PrevalentSystem interface. +* All commands to the system must be represented as objects implementing the Command interface and must be executed using Prevayler.executeCommand(Command). +* Take a look at the demo application included with the Prevayler distribution for examples. +*/ +public class SnapshotPrevaylerImpl implements SnapshotPrevayler { + + private final PrevalentSystem system; + private final SystemClock clock; + private final CommandOutputStream output; + + + /** Returns a new Prevayler for the given PrevalentSystem. + * "PrevalenceBase" shall be the directory where the snapshot and log files shall be created and read. + * @param newSystem The newly started, "empty" PrevalentSystem that will be used as a starting point for every system startup, until the first snapshot is taken. + * @param shouldReset Whether to issue resets in the underlying OOS + */ + public SnapshotPrevaylerImpl(PrevalentSystem newSystem, + boolean shouldReset, boolean shouldClean, + int aBufferSize) + throws IOException, ClassNotFoundException { + + this(newSystem, "PrevalenceBase", shouldReset, shouldClean, + aBufferSize); + } + + + /** Returns a new Prevayler for the given PrevalentSystem. + * @param newSystem The newly started, "empty" PrevalentSystem that will be used as a starting point for every system startup, until the first snapshot is taken. + * @param directory The full path of the directory where the snapshot and log files shall be created and read. + * @param shouldReset Whether to issue resets in the underlying OOS + */ + public SnapshotPrevaylerImpl(PrevalentSystem newSystem, String directory, + boolean shouldReset, boolean shouldClean, + int aBufferSize) + throws IOException, ClassNotFoundException { + + newSystem.clock(new SystemClock()); + CommandInputStream input = new CommandInputStream(directory); + + PrevalentSystem savedSystem = input.readLastSnapshot(); + system = (savedSystem == null) + ? newSystem + : savedSystem; + + recoverCommands(input); + + output = input.commandOutputStream(shouldReset, shouldClean, + aBufferSize); + clock = (SystemClock)system.clock(); + clock.resume(); + } + + public SnapshotPrevaylerImpl(PrevalentSystem newSystem, String directory) + throws IOException, ClassNotFoundException { + + clock = null; + output = null; + + newSystem.clock(new SystemClock()); + CommandInputStream input = new CommandInputStream(directory); + + PrevalentSystem savedSystem = input.readLastSnapshot(); + + if (savedSystem != null) + system = savedSystem; + else + system = newSystem; + + System.out.println("System base clock: " + system.clock().time().getTime()); + Serializable[] myUserData = system.getSnapshotContributions(); + + for (int i = 0; i < myUserData.length; i++) { + System.out.println(myUserData[i].toString()); + } + + debugCommands(input); + } + + /** + Returns the underlying PrevalentSystem. + */ + public PrevalentSystem system() { + return system; + } + + /** Logs the received command for crash or shutdown recovery and executes it on the underlying PrevalentSystem. + * @see system() + * @return The serializable object that was returned by the execution of command. + * @throws IOException if there is trouble writing the command to the log. + * @throws Exception if command.execute() throws an exception. + */ + public Serializable executeCommand(Command command) throws Exception { + + synchronized(this) { + try { + clock.pause(); //To be deterministic, the system must know exactly at what time the command is being executed. + output.writeCommand(new ClockRecoveryCommand(command, clock.time())); + } finally { + clock.resume(); + } + } + + return command.execute(system); + } + + public Serializable executeCommand(Command command, + boolean doSync) + throws Exception { + + synchronized(this) { + try { + clock.pause(); + output.writeCommand(new ClockRecoveryCommand(command, + clock.time()), + doSync); + } finally { + clock.resume(); + } + } + + return command.execute(system); + } + + /** + * This method prepares a snapshot of the system and returns it in a + * Snapshotter instance which can be used to save the snapshot to disk + * once dirty state has been sync'd to disk. If your application has no + * additional state, you can simply invoke on the Snapshotter immediately. + * @return Snapshotter to be used to save an appropriate snapshot post + * sync'ing of dirty state to disk. + * @see system() + * @throws IOException if there is trouble preparing the snapshot file. + */ + public synchronized Snapshotter takeSnapshot() throws IOException { + clock.pause(); + try { + return output.writeSnapshot(system); + } finally { + clock.resume(); + } + } + + private void debugCommands(CommandInputStream input) throws IOException, ClassNotFoundException { + Command command; + while(true) { + try { + command = input.readCommand(); + } catch (EOFException eof) { + break; + } + + try { + System.out.println(command); + System.out.println(); + // command.execute(system); + } catch (Exception e) { + //Don't do anything at all. Commands may throw exceptions normally. + System.err.println("Command threw exception"); + e.printStackTrace(System.err); + } + } + } + + private void recoverCommands(CommandInputStream input) throws IOException, ClassNotFoundException { + Command command; + while(true) { + try { + command = input.readCommand(); + } catch (EOFException eof) { + break; + } + + try { + command.execute(system); + } catch (Exception e) { + //Don't do anything at all. Commands may throw exceptions normally. + System.err.println("Command threw exception"); + e.printStackTrace(System.err); + } + } + } + + public static void main(String anArgs[]) { + try { + System.setSecurityManager(new RMISecurityManager()); + + new SnapshotPrevaylerImpl(new DebugSystem(), anArgs[0]); + } catch (Exception anE) { + System.err.println("Whoops"); + anE.printStackTrace(System.err); + } + } + + static class DebugSystem implements org.prevayler.PrevalentSystem { + private org.prevayler.AlarmClock theClock; + + public void clock(org.prevayler.AlarmClock clock) { + theClock = clock; + } + + public org.prevayler.AlarmClock clock() { + return theClock; + } + + public void add(SnapshotContributor aContributor) { + } + + public void remove(SnapshotContributor aContributor) { + } + + public Serializable[] getSnapshotContributions() { + return new Serializable[0]; + } + } +}