/*
* org.openmicroscopy.shoola.env.init.Initializer
*
*------------------------------------------------------------------------------
* Copyright (C) 2006 University of Dundee. All rights reserved.
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program 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, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
*------------------------------------------------------------------------------
*/
package org.openmicroscopy.shoola.env.init;
//Java imports
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.Stack;
//Third-party libraries
//Application-internal dependencies
import org.openmicroscopy.shoola.env.Container;
/**
* Manages the initialization procedure -- creates all needed initialization
* tasks, configures them, queues them up for execution, and finally executes
* all those tasks.
* <p>Tasks are encapsulated by objects (concrete instances of
* {@link InitializationTask}) and treated as commands -- this class manages
* their execution, acting as a Command Processor.</p>
* <p>This class is also responsible for configuring the initialization
* procedure, which involves creating all tasks, calling their
* <code>configure</code> method and decide on the execution order -- thus, it
* also takes on the role of a Controller.</p>
* <p>Finally, this class allows {@link InitializationListener}s to subscribe
* for notification of initialization procedure progress -- in this regard, it
* plays the role of a Publisher.</p>
*
* @author Jean-Marie Burel
* <a href="mailto:j.burel@dundee.ac.uk">j.burel@dundee.ac.uk</a>
* @author <br>Andrea Falconi
* <a href="mailto:a.falconi@dundee.ac.uk">
* a.falconi@dundee.ac.uk</a>
* @version 2.2
* <small>
* (<b>Internal version:</b> $Revision$ $Date$)
* </small>
* @since OME2.2
*/
public class Initializer
{
/**
* Lists the tasks that will make up the initialization sequence.
* Note that this list can be accessed by subclasses. This is key in
* testing environments because initialization tasks can be replaced
* with tasks that provide service stubs to remove problematic
* dependencies on external resources.
*/
protected static final List<Class<?>> initList = new ArrayList<Class<?>>();
static {
//This must be the first task to run b/c it will bring up
//the splash screen.
//initList.add(SplashScreenInit.class);
//NB: All tasks require this one to be run first
//(b/c it creates and fills up the container's config).
initList.add(ContainerConfigInit.class);
initList.add(SplashScreenInit.class);
initList.add(LoggerInit.class);
initList.add(CacheInit.class);
initList.add(EventBusInit.class);
initList.add(CmdProcessorInit.class);
initList.add(DataServicesInit.class);
initList.add(RenderingServicesInit.class);
initList.add(LoginServiceInit.class);
initList.add(TaskBarInit.class);
initList.add(UserNotifierInit.class);
initList.add(AgentsInit.class);
}
/**
* Instantiates the specified initialization task and links it to the
* passed {@link Container} and {@link Initializer}.
*
* @param taskType The class of the task. Mustn't be <code>null</code>.
* @param c Reference to the {@link Container}.
* Mustn't be <code>null</code>.
* @param i Reference to the {@link Initializer}.
* Mustn't be <code>null</code>.
* @return An instance of the requested task type.
* @throws StartupException If the task couldn't be created.
*/
private static InitializationTask createInitTask(Object taskType,
Container c, Initializer i)
throws StartupException
{
//Sanity checks.
if (taskType == null) throw new NullPointerException("No task type.");
if (c == null) throw new NullPointerException("No container.");
if (i == null) throw new NullPointerException("No initializer.");
//Instantiate through reflection, then link to c and i.
InitializationTask task = null;
try {
Class<?> taskClass = (Class<?>) taskType;
task = (InitializationTask) taskClass.newInstance();
task.linkContainer(c);
task.linkInitializer(i);
} catch (InstantiationException ie) {
throw new StartupException(
"Couldn't instantiate initialization task.", ie);
} catch (IllegalAccessException iae) {
throw new StartupException(
"Couldn't instantiate initialization task.", iae);
} catch (ClassCastException cce) {
throw new StartupException(
"Invalid initialization task: "+
taskType+" doesn't extends InitializationTask.");
}
return task;
}
/** Queue to order the tasks to be executed. */
private List<InitializationTask> processingQueue;
/** The task that is currently processed. */
private InitializationTask currentTask;
/** The tasks that have currently been executed. */
private Stack<InitializationTask> doneTasks;
/** The notification set for initialization progress. */
private Set<InitializationListener> initListeners;
/** A reference to the singleton {@link Container}. */
private Container container;
/**
* Calls the <code>onStart</code> method of each subscriber in the
* notification set.
*/
private void notifyStart()
{
int size = processingQueue.size()-2;
Iterator<InitializationListener> i = initListeners.iterator();
while (i.hasNext())
i.next().onStart(size);
}
/**
* Calls the <code>onExecute</code> method of each subscriber in the
* notification set.
*/
private void notifyExecute()
{
String name = currentTask.getName();
Iterator<InitializationListener> i = initListeners.iterator();
while (i.hasNext())
i.next().onExecute(name);
}
/**
* Calls the <code>onEnd</code> method of each subscriber in the
* notification set.
*/
public void notifyEnd()
{
Iterator<InitializationListener> i = initListeners.iterator();
while (i.hasNext())
i.next().onEnd();
//Allow for referenced objects to be garbage collected (see below).
currentTask = null;
processingQueue = null;
initListeners = null;
//Now control goes into container object, so this object won't be
//garbage collected until startService() returns, which may be on exit.
container.startService();
}
/**
* Only for the benefit of subclasses that want to modify the
* {@link #initList}.
* This should only be done for the purpose of testing.
*/
protected Initializer() {}
/**
* Creates a new instance.
* The {@link Container} is the only class that can possibly create this
* object. In fact, the {@link Container} is the only class to have
* a reference to the singleton {@link Container}.
*
* @param c A reference to the singleton {@link Container}.
*/
public Initializer(Container c)
{
this(c, false);
}
/**
* Creates a new instance.
* The {@link Container} is the only class that can possibly create this
* object. In fact, the {@link Container} is the only class to have
* a reference to the singleton {@link Container}.
*
* @param c A reference to the singleton {@link Container}.
* @param headless Flag indicating to start the application head-less or not.
*/
public Initializer(Container c, boolean headless)
{
if (c == null) throw new NullPointerException();
processingQueue = new ArrayList<InitializationTask>();
doneTasks = new Stack<InitializationTask>();
initListeners = new HashSet<InitializationListener>();
if (headless) initList.remove(SplashScreenInit.class);
container = c;
}
/**
* Creates all needed initialization tasks, configures them, and queues
* them up for execution.
* This method has to be called before {@link #doInit()}.
*
* @throws StartupException If an error occurs while configuring an
* initialization task.
*/
public void configure()
throws StartupException
{
InitializationTask task;
Iterator<Class<?>> type = initList.iterator();
while (type.hasNext()) {
task = createInitTask(type.next(), container, this);
task.configure();
processingQueue.add(task);
}
}
/**
* Performs the initialization procedure.
*
* @throws StartupException If an error occurs while executing an
* initialization task.
*/
public void doInit()
throws StartupException
{
Iterator<InitializationTask> i = processingQueue.iterator();
//Tell all listeners that we're about to start.
notifyStart();
//Execute all pending tasks.
while (i.hasNext()) {
currentTask = i.next();
notifyExecute(); //Tell listeners we're about to exec a task.
currentTask.execute();
doneTasks.push(currentTask); //For later rollback if needed.
}
/*
//Tell all listeners that we're finished.
notifyEnd();
//Allow for referenced objects to be garbage collected (see below).
currentTask = null;
processingQueue = null;
initListeners = null;
//Now control goes into container object, so this object won't be
//garbage collected until startService() returns, which may be on exit.
container.startService();
*/
}
/**
* Rolls back all tasks that have been executed at the time this method
* is invoked.
*/
public void rollback()
{
Iterator<InitializationTask> i = doneTasks.iterator();
while (i.hasNext())
i.next().rollback();
}
/**
* Adds the specified initialization listener to the notification set.
*
* @param subscriber The listener.
* @return <code>true</code> if <code>subscriber</code> is not already in
* the notification set, <code>false</code> otherwise.
* @throws NullPointerException If <code>null</code> is passed in.
*/
public boolean register(InitializationListener subscriber)
{
if (subscriber == null) throw new NullPointerException();
return initListeners.add(subscriber);
}
}