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/**
* Copyright (c) 2002-2006 IBM Corporation 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:
* IBM - Initial API and implementation
*/
package org.eclipse.emf.common.command;
import java.util.Collection;
import java.util.Collections;
import org.eclipse.emf.common.CommonPlugin;
/**
* A command that wraps another command.
* All the {@link Command} methods are delegated to the wrapped command.
*
*
* There are two typical usage patterns.
* One typical use for this command is to modify the behaviour of a command that you can't subclass, i.e., a decorator pattern:
*
* Command decoratedCommand =
* new CommandWrapper(someOtherCommand)
* {
* public void execute()
* {
* doSomethingBeforeExecution();
* super.execute();
* doSomethingAfterExecution();
* }
* public Collection getResult()
* {
* return someOtherResult();
* }
* };
*
* The other typical use is to act as a proxy for a command who's creation is delayed:
*
* Command proxyCommand =
* new CommandWrapper()
* {
* public Command createCommand()
* {
* return createACommandSomehow();
* }
* };
*
*/
public class CommandWrapper extends AbstractCommand
{
/**
* The command for which this is a proxy or decorator.
*/
protected Command command;
/**
* Creates a decorator instance for the given command.
* @param command the command to wrap.
*/
public CommandWrapper(Command command)
{
super(command.getLabel(), command.getDescription());
this.command = command;
}
/**
* Creates a decorator instance with the given label for the given command.
* @param label the label of the wrapper
* @param command the command to wrap.
*/
protected CommandWrapper(String label, Command command)
{
super(label, command.getDescription());
this.command = command;
}
/**
* Creates a decorator instance with the given label and description for the given command.
* @param label the label of the wrapper
* @param description the description of the wrapper
* @param command the command to wrap.
*/
public CommandWrapper(String label, String description, Command command)
{
super(label, description);
this.command = command;
}
/**
* Creates a commandless proxy instance.
* The wrapped command will be created by a {@link #createCommand} callback.
* Since a proxy command like this is pointless unless you override some method, this constructor is protected.
*/
protected CommandWrapper()
{
super();
}
/**
* Creates a commandless proxy instance, with the given label.
* The command will be created by a {@link #createCommand} callback.
* Since a proxy command like this is pointless unless you override some method, this constructor is protected.
* @param label the label of the wrapper
*/
protected CommandWrapper(String label)
{
super(label);
}
/**
* Creates a commandless proxy instance, with the given label and description.
* The command will be created by a {@link #createCommand} callback.
* Since a proxy command like this is pointless unless you override some method, this constructor is protected.
* @param label the label of the wrapper
* @param description the description of the wrapper
*/
protected CommandWrapper(String label, String description)
{
super(label, description);
}
/**
* Returns the command for which this is a proxy or decorator.
* This may be null before {@link #createCommand} is called.
* @return the command for which this is a proxy or decorator.
*/
public Command getCommand()
{
return command;
}
/**
* Create the command being proxied.
* This implementation just return null.
* It is called by {@link #prepare}.
* @return the command being proxied.
*/
protected Command createCommand()
{
return null;
}
/**
* Returns whether the command can execute.
* This implementation creates the command being proxied using {@link #createCommand},
* if the command wasn't given in the constructor.
* @return whether the command can execute.
*/
@Override
protected boolean prepare()
{
if (command == null)
{
command = createCommand();
}
boolean result = command.canExecute();
return result;
}
/**
* Delegates to the execute method of the command.
*/
public void execute()
{
if (command != null)
{
command.execute();
}
}
/**
* Delegates to the canUndo method of the command.
*/
@Override
public boolean canUndo()
{
return command == null || command.canUndo();
}
/**
* Delegates to the undo method of the command.
*/
@Override
public void undo()
{
if (command != null)
{
command.undo();
}
}
/**
* Delegates to the redo method of the command.
*/
public void redo()
{
if (command != null)
{
command.redo();
}
}
/**
* Delegates to the getResult method of the command.
* @return the result.
*/
@Override
public Collection getResult()
{
return
command == null ?
Collections.EMPTY_LIST :
command.getResult();
}
/**
* Delegates to the getAffectedObjects method of the command.
* @return the result.
*/
@Override
public Collection getAffectedObjects()
{
return
command == null ?
Collections.EMPTY_LIST :
command.getAffectedObjects();
}
/**
* Delegates to the getLabel method of the command.
* @return the label.
*/
@Override
public String getLabel()
{
return
label == null ?
command == null ?
CommonPlugin.INSTANCE.getString("_UI_CommandWrapper_label") :
command.getLabel() :
label;
}
/**
* Delegates to the getDescription method of the command.
* @return the description.
*/
@Override
public String getDescription()
{
return
description == null ?
command == null ?
CommonPlugin.INSTANCE.getString("_UI_CommandWrapper_description") :
command.getDescription() :
description;
}
/**
* Delegates to the dispose method of the command.
*/
@Override
public void dispose()
{
if (command != null)
{
command.dispose();
}
}
/*
* Javadoc copied from base class.
*/
@Override
public String toString()
{
StringBuffer result = new StringBuffer(super.toString());
result.append(" (command: " + command + ")");
return result.toString();
}
}