net.sf.jguiraffe.gui.cmd

Class CommandBase

java.lang.Object

net.sf.jguiraffe.gui.cmd.CommandBase

All Implemented Interfaces:

Command

Direct Known Subclasses:

BgTaskCommand, CreateFileCommand, CreateViewSettingsCommand, OpenWindowCommand

public abstract class CommandBase
extends Object
implements Command

An abstract base class for implementations of the Command interface.

This abstract class provides some simple base implementations for methods required by the Command interface. It also defines some utility methods that are useful in GUI applications.

The main execution method of course must be implemented in concrete sub classes. The onException() method passes the exception to a logger. For onFinally() an empty dummy implementation is provided. GUI updates can be performed in the performGUIUpdate() method. This method will be executed by a Runnable object in the application's event handler thread if the UpdateGUI property is set to true.

Version:

$Id: CommandBase.java 205 2012-01-29 18:29:57Z oheger $

Author:

Oliver Heger

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	CommandBase() Creates a new instance of CommandBase.
protected	CommandBase(boolean updateGUI) Creates a new instance of CommandBase and sets the UpdateGUI property.

Method Summary

Modifier and Type	Method and Description
Throwable	getException() Returns an exception that was thrown during the execution of this command.
Runnable	getGUIUpdater() Returns a Runnable object for updating the GUI.
protected org.apache.commons.logging.Log	getLog() Returns the logger used by this object.
boolean	isUpdateGUI() Returns the value of the UpdateGUI property.
void	onException(Throwable t) This method is called if an exception occurs.
void	onFinally() This method is called after each command execution.
protected void	performGUIUpdate() Performs GUI updates.
void	setException(Throwable exception) Sets an exception that was thrown during the execution of this command.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface net.sf.jguiraffe.gui.cmd.Command

execute

Constructor Detail

CommandBase

protected CommandBase()

Creates a new instance of CommandBase. The UpdateGUI property is set to true.

CommandBase

protected CommandBase(boolean updateGUI)

Creates a new instance of CommandBase and sets the UpdateGUI property.

Parameters:

updateGUI - a flag if GUI updates are to be performed

Method Detail

onException

public void onException(Throwable t)

This method is called if an exception occurs. This implementation calls setException(Throwable) to store the exception.

Specified by:

onException in interface Command

Parameters:

t - the exception

onFinally

public void onFinally()

This method is called after each command execution. This is an empty dummy implementation.

Specified by:

onFinally in interface Command

getGUIUpdater

public Runnable getGUIUpdater()

Returns a Runnable object for updating the GUI. This implementation returns either null or a Runnable object that invokes the performGUIUpdate() method, depending on the value of the UpdateGUI property.

Specified by:

getGUIUpdater in interface Command

Returns:

an object for updating the GUI

isUpdateGUI

public boolean isUpdateGUI()

Returns the value of the UpdateGUI property. This flag can be set in the constructor. If set to true, the performGUIUpdate() method will be invoked on the event dispatch thread after the command was executed. If a derived class needs a more complex logic that can be implemented using a final flag, it can override this method to return a value that is computed based on arbitrary criteria.

Returns:

the UpdateGUI property

getException

public Throwable getException()

Returns an exception that was thrown during the execution of this command. Result can be null, which means that no exception was thrown.

Returns:

an exception thrown during the execution of this command

setException

public void setException(Throwable exception)

Sets an exception that was thrown during the execution of this command. The onException(Throwable) implementation invokes this method to store the exception passed to this method. It can then be queried by the methods invoked later in the command's life-cycle (e.g. onFinally() or performGUIUpdate()) to find out whether the command's execution was successful.

Parameters:

exception - an exception

getLog

protected org.apache.commons.logging.Log getLog()

Returns the logger used by this object.

Returns:

the logger

performGUIUpdate

protected void performGUIUpdate()

Performs GUI updates. Here the code for thread safe GUI updates can be placed. If the UpdateGUI property is set, this method will automatically be invoked in the event dispatch thread after the command has been executed (also if an exception was thrown - in this case the exception can be queried using the getException() method). This base implementation is empty.