ptolemy.util
Class MessageHandler

java.lang.Object
  ptolemy.util.MessageHandler

public class MessageHandler
extends java.lang.Object

This is a class that is used to report errors. It provides a set of static methods that are called to report errors. However, the actual reporting of the errors is deferred to an instance of this class that is set using the setMessageHandler() method. Normally there is only one instance, set up by the application, so the class is a singleton. But this is not enforced.

This base class simply writes the errors to System.err. When an applet or application starts up, it may wish to set a subclass of this class as the message handler, to allow a nicer way of reporting errors. For example, a Swing application will probably want to report errors in a dialog box, using for example the derived class GraphicalMessageHandler.

Since:

Ptolemy II 4.0

Version:

$Id: MessageHandler.java 57040 2010-01-27 20:52:32Z cxh $

Author:

Edward A. Lee, Steve Neuendorffer, Elaine Cheong

See Also:

ptolemy.gui.GraphicalMessageHandler

Accepted Rating:

Green (cxh)

Proposed Rating:

Green (cxh)

Field Summary

private static MessageHandler

_handler

Constructor Summary

MessageHandler()

Method Summary

protected void	_error(java.lang.String info) Show the specified error message.
protected void	_error(java.lang.String info, java.lang.Throwable throwable) Show the specified message and throwable information.
protected void	_message(java.lang.String info) Display the warning message.
protected void	_warning(java.lang.String info) Show the specified message.
protected void	_warning(java.lang.String info, java.lang.Throwable throwable) Display the warning message and throwable information.
protected boolean	_yesNoCancelQuestion(java.lang.String question) Ask the user a yes/no/cancel question, and return true if the answer is yes.
protected boolean	_yesNoQuestion(java.lang.String question) Ask the user a yes/no question, and return true if the answer is yes.
static void	error(java.lang.String info) Defer to the set message handler to show the specified error message.
static void	error(java.lang.String info, java.lang.Throwable throwable) Defer to the set message handler to show the specified message and throwable information.
static MessageHandler	getMessageHandler() Return the message handler instance that is used by the static methods in this class.
static void	message(java.lang.String info) Defer to the set message handler to show the specified message.
static void	setMessageHandler(MessageHandler handler) Set the message handler instance that is used by the static methods in this class.
static java.lang.String	shortDescription(java.lang.Throwable throwable) Return a short description of the throwable.
static void	warning(java.lang.String info) Display the warning message.
static void	warning(java.lang.String info, java.lang.Throwable throwable) Display the warning message and throwable information.
static boolean	yesNoCancelQuestion(java.lang.String question) Ask the user a yes/no/cancel question, and return true if the answer is yes.
static boolean	yesNoQuestion(java.lang.String question) Ask the user a yes/no question, and return true if the answer is yes.

Methods inherited from class java.lang.Object

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

Field Detail

_handler

private static MessageHandler _handler

Constructor Detail

MessageHandler

public MessageHandler()

Method Detail

error

public static void error(java.lang.String info)

Defer to the set message handler to show the specified error message.

Parameters:

info - The message.

error

public static void error(java.lang.String info,
                         java.lang.Throwable throwable)

Defer to the set message handler to show the specified message and throwable information. If the throwable is an instance of CancelException, then it is not shown.

Parameters:

info - The message.

throwable - The throwable.

See Also:

CancelException

getMessageHandler

public static MessageHandler getMessageHandler()

Return the message handler instance that is used by the static methods in this class.

Returns:

The message handler.

See Also:

setMessageHandler(MessageHandler)

message

public static void message(java.lang.String info)

Defer to the set message handler to show the specified message.

Parameters:

info - The message.

setMessageHandler

public static void setMessageHandler(MessageHandler handler)

Set the message handler instance that is used by the static methods in this class. If the given handler is null, then do nothing.

Parameters:

handler - The message handler.

See Also:

getMessageHandler()

shortDescription

public static java.lang.String shortDescription(java.lang.Throwable throwable)

Return a short description of the throwable.

Parameters:

throwable - The throwable

Returns:

If the throwable is an Exception, return "Exception", if it is an Error, return "Error", if it is a Throwable, return "Throwable".

warning

public static void warning(java.lang.String info)
                    throws CancelException

Display the warning message. In this base class, the the default handler merely prints the warning to stderr. Derived classes such as ptolemy.gui.GraphicalMessageHandler might display the message graphically.

Parameters:

info - The message.

Throws:

CancelException - If the user clicks on the "Cancel" button.

warning

public static void warning(java.lang.String info,
                           java.lang.Throwable throwable)
                    throws CancelException

Display the warning message and throwable information. In this base class, the the default handler merely prints the warning to stderr. Derived classes such as ptolemy.gui.GraphicalMessageHandler might display the message graphically.

Parameters:

info - The message.

throwable - The throwable associated with this warning.

Throws:

CancelException - If the user clicks on the "Cancel" button.

yesNoQuestion

public static boolean yesNoQuestion(java.lang.String question)

Ask the user a yes/no question, and return true if the answer is yes.

Parameters:

question - The yes/no question.

Returns:

True if the answer is yes.

yesNoCancelQuestion

public static boolean yesNoCancelQuestion(java.lang.String question)
                                   throws CancelException

Ask the user a yes/no/cancel question, and return true if the answer is yes. If the user clicks on the "Cancel" button, then throw an exception.

Parameters:

question - The yes/no/cancel question.

Returns:

True if the answer is yes.

Throws:

CancelException - If the user clicks on the "Cancel" button.

_error

protected void _error(java.lang.String info)

Show the specified error message.

Parameters:

info - The message.

_error

protected void _error(java.lang.String info,
                      java.lang.Throwable throwable)

Show the specified message and throwable information. If the throwable is an instance of CancelException, then nothing is shown.

Parameters:

info - The message.

throwable - The throwable.

See Also:

CancelException

_message

protected void _message(java.lang.String info)

Display the warning message. In this base class, the the default handler merely prints the warning to stderr.

Parameters:

info - The message.

_warning

protected void _warning(java.lang.String info)
                 throws CancelException

Show the specified message. In this base class, the message is printed to standard error.

Derived classes might show the specified message in a modal dialog. If the user clicks on the "Cancel" button, then throw an exception. This gives the user the option of not continuing the execution, something that is particularly useful if continuing execution will result in repeated warnings.

Parameters:

info - The message.

Throws:

CancelException - If the user clicks on the "Cancel" button.

_warning

protected void _warning(java.lang.String info,
                        java.lang.Throwable throwable)
                 throws CancelException

Display the warning message and throwable information. In this base class, the the default handler merely prints the warning to stderr.

Parameters:

info - The message.

throwable - The Throwable.

Throws:

CancelException - If the user clicks on the "Cancel" button.

_yesNoQuestion

protected boolean _yesNoQuestion(java.lang.String question)

Ask the user a yes/no question, and return true if the answer is yes. In this base class, this prints the question on standard output and looks for the reply on standard input.

Parameters:

question - The yes/no question to be asked.

Returns:

True if the answer is yes.

_yesNoCancelQuestion

protected boolean _yesNoCancelQuestion(java.lang.String question)
                                throws CancelException

Ask the user a yes/no/cancel question, and return true if the answer is yes. If the user chooses "cancel", then throw an exception. In this base class, this prints the question on the standard output and looks for the reply on the standard input.

Parameters:

question - The yes/no/cancel question to be asked.

Returns:

True if the answer is yes.

Throws:

CancelException - If the user chooses "cancel".