/*
* Copyright 2007-2009 Sun Microsystems, Inc.
*
* This file is part of Project Darkstar Server.
*
* Project Darkstar Server is free software: you can redistribute it
* and/or modify it under the terms of the GNU General Public License
* version 2 as published by the Free Software Foundation and
* distributed hereunder to you.
*
* Project Darkstar Server 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 for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.sun.sgs.tutorial.server.lesson4;
import java.io.Serializable;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;
import com.sun.sgs.app.AppContext;
import com.sun.sgs.app.AppListener;
import com.sun.sgs.app.ClientSession;
import com.sun.sgs.app.ClientSessionListener;
import com.sun.sgs.app.DataManager;
import com.sun.sgs.app.ManagedReference;
import com.sun.sgs.app.Task;
import com.sun.sgs.app.TaskManager;
/**
* A simple persistence example for the Project Darkstar Server.
*/
public class HelloPersistence3
implements AppListener, Serializable, Task
{
/** The version of the serialized form of this class. */
private static final long serialVersionUID = 1L;
/** The {@link Logger} for this class. */
private static final Logger logger =
Logger.getLogger(HelloPersistence3.class.getName());
/** The delay before the first run of the task. */
public static final int DELAY_MS = 5000;
/** The time to wait before repeating the task. */
public static final int PERIOD_MS = 500;
/** A reference to our subtask, a {@link TrivialTimedTask}. */
private ManagedReference<TrivialTimedTask> subTaskRef = null;
/**
* Gets the subtask this task delegates to. Dereferences a
* {@link ManagedReference} in this object that holds the subtask.
* <p>
* This null-check idiom is common when getting a ManagedReference.
*
* @return the subtask this task delegates to, or null if none is set
*/
public TrivialTimedTask getSubTask() {
if (subTaskRef == null) {
return null;
}
return subTaskRef.get();
}
/**
* Sets the subtask this task delegates to. Stores the subtask
* as a {@link ManagedReference} in this object.
* <p>
* This null-check idiom is common when setting a ManagedReference,
* since {@link DataManager#createReference createReference} does
* not accept null parameters.
*
* @param subTask the subtask this task should delegate to,
* or null to clear the subtask
*/
public void setSubTask(TrivialTimedTask subTask) {
if (subTask == null) {
subTaskRef = null;
return;
}
DataManager dataManager = AppContext.getDataManager();
subTaskRef = dataManager.createReference(subTask);
}
// implement AppListener
/**
* {@inheritDoc}
* <p>
* Schedules the {@code run()} method of this object to be called
* periodically.
* <p>
* Since SGS tasks are persistent, the scheduling only needs to
* be done the first time the application is started. When the
* server is killed and restarted, the scheduled timer task will
* continue ticking.
* <p>
* Runs the task {@value #DELAY_MS} ms from now,
* repeating every {@value #PERIOD_MS} ms.
*/
public void initialize(Properties props) {
// Hold onto the task (as a managed reference)
setSubTask(new TrivialTimedTask());
TaskManager taskManager = AppContext.getTaskManager();
taskManager.schedulePeriodicTask(this, DELAY_MS, PERIOD_MS);
}
/**
* {@inheritDoc}
* <p>
* Prevents client logins by returning {@code null}.
*/
public ClientSessionListener loggedIn(ClientSession session) {
return null;
}
// implement Task
/**
* {@inheritDoc}
* <p>
* Calls the run() method of the subtask set on this object.
*/
public void run() throws Exception {
// Get the subTask (from the ManagedReference that holds it)
TrivialTimedTask subTask = getSubTask();
if (subTask == null) {
logger.log(Level.WARNING, "subTask is null");
return;
}
// Delegate to the subTask's run() method
subTask.run();
}
}