/*
* org.openmicroscopy.shoola.env.data.events.DSCallOutcomeEvent
*
*------------------------------------------------------------------------------
* 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.data.events;
//Java imports
//Third-party libraries
//Application-internal dependencies
import org.openmicroscopy.shoola.env.event.StateChangeEvent;
/**
* Notfies of the outcome of an asynchronous call to the data services.
*
* @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 DSCallOutcomeEvent
extends StateChangeEvent
{
/**
* Outcome state flag to denote that the call was cancelled.
* In this state both the {@link #getResult() getResult} and
* {@link #getException() getException} methods will return
* <code>null</code>.
*/
public static final int CANCELLED = 0;
/**
* Outcome state flag to denote that the call raised an exception.
* In this state the {@link #getException() getException} method
* will return the exception that was thrown.
* The {@link #getResult() getResult} method will obviously return
* <code>null</code>.
*/
public static final int ERROR = 1;
/**
* Outcome state flag to denote that the call returned with a
* <code>null</code> result.
* This can happen if the operation itself returns no value or
* it does have a return value, but this specific invocation
* returned <code>null</code>.
* In this state both the {@link #getResult() getResult} and
* {@link #getException() getException} methods will return
* <code>null</code>.
*/
public static final int NO_RESULT = 2;
/**
* Outcome state flag to denote that the call returned a result.
* In this state the {@link #getResult() getResult} method will
* return the produced result (which is never <code>null</code>
* in this case). The {@link #getException() getException} method
* method will obviously return <code>null</code>.
*/
public static final int HAS_RESULT = 3;
/** Keeps track of the state. */
private final int state;
/** The result (if any) of the call. */
private final Object result;
/** Any exception raised by the call. */
private final Throwable exception;
/**
* Constructor used in the case of cancellation.
*/
public DSCallOutcomeEvent()
{
result = null;
exception = null;
state = CANCELLED;
setStateChange(this);
}
/**
* Constructor used in the case the call terminates regularly.
*
* @param result The result of the call. Pass <code>null</code> if the
* call returns no results.
*/
public DSCallOutcomeEvent(Object result)
{
exception = null;
this.result = result;
state = (result == null) ? NO_RESULT : HAS_RESULT;
setStateChange(this);
}
/**
* Constructor used in the case the call raises an exception.
*
* @param exception The raised error. Mustn't be <code>null</code>.
*/
public DSCallOutcomeEvent(Throwable exception)
{
if (exception == null)
throw new NullPointerException("Must specify a Throwable.");
this.exception = exception;
result = null;
state = ERROR;
setStateChange(this);
}
/**
* Returns the outcome state.
*
* @return One of the static state flags defined by this class.
*/
public int getState() { return state; }
/**
* Tells whether the call was cancelled.
*
* @return <code>true</code> if cancelled, <code>false</code> otherwise.
* @see #CANCELLED
*/
public boolean wasCancelled() { return (state == CANCELLED); }
/**
* Tells whether an exeption was raised during the call.
*
* @return <code>true</code> if an exeption was raised, <code>false</code>
* otherwise.
* @see #ERROR
*/
public boolean hasException() { return (state == ERROR); }
/**
* Tells whether the call produced a result.
* If this method returns <code>true</code>, then the call completed
* normally and produced a non-<code>null</code> result, which can be
* retrieved through the {@link #getResult() getResult} method. If
* <code>false</code> is returned instead, then no result is available
* and calling {@link #getResult()} would return <code>null</code>.
* This can happen because one of the following:
* <ul>
* <li>The call was cancelled.</li>
* <li>The call raised an exception.</li>
* <li>The operation itself returns no value or it does have a return
* value, but this specific invocation returned <code>null</code>.</li>
* </ul>
*
* @return <code>true</code> if there's a return value, <code>false</code>
* otherwise.
* @see #HAS_RESULT
* @see #NO_RESULT
* @see #ERROR
* @see #CANCELLED
*/
public boolean hasResult() { return (state == HAS_RESULT); }
/**
* Returns any exception raised during the call.
* Will always return <code>null</code> if the call was
* {@link #CANCELLED cancelled} or terminated regularly.
*
* @return The exception that was thrown. It's a non-<code>null</code>
* reference that you'll have to cast to a more suitable type as
* documented by the call. However, keep in mind that other
* exceptions are possible besides those documented by the call.
* In fact, <i>any</i> exception occurred during the computation
* will be caught and eventually packed in this object.
* @see #hasException()
*/
public Throwable getException() { return exception; }
/**
* Returns the result (if any) of the call.
* This method will always return <code>null</code> if the call was
* {@link #wasCancelled() cancelled} or an exception
* {@link #hasException() raised}. However, even if the call returned
* normally, a <code>null</code> value is still possible if the call
* produces no results, or the actual result returned by the call is
* <code>null</code>.
*
* @return The result of the call. It's a non-<code>null</code> reference
* that you'll have to cast to a more suitable type as documented
* by the call.
*/
public Object getResult() { return result; }
}