/*******************************************************************************
* Copyright (c) 2012, 2014 EclipseSource and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* EclipseSource - initial API and implementation
******************************************************************************/
package org.eclipse.rap.rwt;
import org.eclipse.rap.rwt.internal.SingletonManager;
import org.eclipse.rap.rwt.internal.util.ParamCheck;
import org.eclipse.rap.rwt.service.ApplicationContext;
import org.eclipse.rap.rwt.service.UISession;
/**
* Creates and maintains a unique instance of a given type for the given scope. The scope is either
* a UI session or an application context. Within the context of this scope,
* <code>getUniqueInstance(...)</code> will always return the same object, but for different scopes
* the returned instances will be different.
* <p>
* This utility class can be used to adjust classic singletons to the appropriate scope in RAP.
* Example:
* </p>
* <pre>
* public class FooSingleton {
*
* private FooSingleton() {
* }
*
* public static FooSingleton getInstance() {
* return SingletonUtil.getUniqueInstance( FooSingleton.class, RWT.getUISession() );
* }
* }
* </pre>
*
* @since 2.0
*/
public final class SingletonUtil {
/**
* Returns an instance of the specified type that is unique within the current UI session. If no
* such instance exists yet, a new one will be created. The specified type must have a
* parameterless constructor.
* <p>
* This method is a shortcut for
* <code>getUniqueInstance( type, RWT.getUISession() )</code>.
* </p>
*
* @param type the type to obtain a singleton instance for
* @return the unique instance of the specified type that is associated with the current UI
* session
*/
public static <T> T getSessionInstance( Class<T> type ) {
return getUniqueInstance( type, RWT.getUISession() );
}
/**
* Returns an instance of the specified type that is unique within the given UI session. If no
* such instance exists yet, a new one will be created. The specified type must have a
* parameterless constructor.
*
* @param type the type to obtain a singleton instance for
* @param uiSession the UI session to store the singleton instance in
* @return the unique instance of the specified type that is associated with the given UI session
* @since 2.3
*/
public static <T> T getUniqueInstance( Class<T> type, UISession uiSession ) {
ParamCheck.notNull( type, "type" );
ParamCheck.notNull( uiSession, "uiSession" );
return SingletonManager.getInstance( uiSession ).getSingleton( type );
}
/**
* Returns an instance of the specified type that is unique within the given UI session. If no
* such instance exists yet, a new one will be created. The specified type must have a
* parameterless constructor.
*
* @param type the type to obtain a singleton instance for
* @param applicationContext the application context to store the singleton instance in
* @return the unique instance of the specified type that is associated with the given application
* context
* @since 2.3
*/
public static <T> T getUniqueInstance( Class<T> type, ApplicationContext applicationContext ) {
ParamCheck.notNull( type, "type" );
ParamCheck.notNull( applicationContext, "applicationContext" );
return SingletonManager.getInstance( applicationContext ).getSingleton( type );
}
}