| /******************************************************************************* |
| * Copyright (c) 2007, 2012 Oracle. 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: |
| * Oracle - initial API and implementation |
| ******************************************************************************/ |
| package org.eclipse.jpt.common.utility.command; |
| |
| import java.io.Serializable; |
| import org.eclipse.jpt.common.utility.internal.StringTools; |
| |
| /** |
| * This interface allows clients to control how a command is executed. |
| * This is useful when the server provides the command but the client provides |
| * the context (e.g. the client would like to dispatch the command to the UI |
| * thread). |
| * <p> |
| * Provisional API: This interface is part of an interim API that is still |
| * under development and expected to change significantly before reaching |
| * stability. It is available at this early stage to solicit feedback from |
| * pioneering adopters on the understanding that any code that uses this API |
| * will almost certainly be broken (repeatedly) as the API evolves. |
| */ |
| public interface CommandExecutor { |
| |
| /** |
| * Execute the specified command, synchronously or asynchronously. |
| * The commands themselves must be executed in the order in which |
| * they are passed to the command executor (at least when passed |
| * from clients executing on the same thread). |
| */ |
| void execute(Command command); |
| |
| |
| /** |
| * Singleton implementation of the command executor interface |
| * that simply executes the command without any sort of enhancement. |
| */ |
| final class Default |
| implements CommandExecutor, Serializable |
| { |
| public static final CommandExecutor INSTANCE = new Default(); |
| public static CommandExecutor instance() { |
| return INSTANCE; |
| } |
| // ensure single instance |
| private Default() { |
| super(); |
| } |
| public void execute(Command command) { |
| command.execute(); |
| } |
| @Override |
| public String toString() { |
| return StringTools.buildSingletonToString(this); |
| } |
| private static final long serialVersionUID = 1L; |
| private Object readResolve() { |
| // replace this object with the singleton |
| return INSTANCE; |
| } |
| } |
| |
| |
| /** |
| * Singleton implementation of the command executor interface |
| * that ignores any commands. |
| */ |
| final class Inactive |
| implements CommandExecutor, Serializable |
| { |
| public static final CommandExecutor INSTANCE = new Inactive(); |
| public static CommandExecutor instance() { |
| return INSTANCE; |
| } |
| // ensure single instance |
| private Inactive() { |
| super(); |
| } |
| public void execute(Command command) { |
| // do nothing |
| } |
| @Override |
| public String toString() { |
| return StringTools.buildSingletonToString(this); |
| } |
| private static final long serialVersionUID = 1L; |
| private Object readResolve() { |
| // replace this object with the singleton |
| return INSTANCE; |
| } |
| } |
| } |