Bug 121709 [Commands] parameters: Add types
I'm going to attach a patch that adds support for typed command parameters. This addresses several issues: - parameter values are strings, but handlers may want to work on objects - multiple handlers of a command should have a consistent way of converting string parameter values to objects - tooling to construct parameterized commands that starts with object parameter values needs a way of producing string parameter values that will work when the command is executed - there should be a way to classify commands by their object parameter types so, given an object, a set of commands that may work with it can be suggested To address these issues, the patch allows parameter types to be declared in the extension-point XML. The example below defines a command for negating integers and a parameter type that works with it. <extension point="org.eclipse.ui.commands"> <command id="org.example.commands.negateInteger" defaultHandler="org.example.commands.NegateIntegerHandler" name="Negate an Integer"> <commandParameter id="param" name="the param" optional="false" typeId="org.example.commands.Integer"/> </command> <commandParameterType id="org.example.commands.Integer" converter="org.example.commands.IntegerConverter" type="java.lang.Integer"/> </extension> In addition to extending the schema for org.eclipse.ui.commands, code has been added to a number of plugins (primarily org.eclipse.core.commands) to support the notion of typed parameters.
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/Command.java
*             instead.
	 */
	public final Object execute(final ExecutionEvent event)
			throws ExecutionException, NotHandledException {
		firePreExecute(event);
		final IHandler handler = this.handler;
		
		if ((handler != null) && (handler.isHandled())) {
			try {
				final Object returnValue = handler.execute(event);
				firePostExecuteSuccess(returnValue);
				return returnValue;
			} catch (final ExecutionException e) {
				firePostExecuteFailure(e);
				throw e;
			}
		}
		final NotHandledException e = new NotHandledException(
				"There is no handler to execute."); 
		fireNotHandled(e);
		throw e;
	}
	/**
	 * Executes this command by delegating to the current handler, if any. If
	 * the debugging flag is set, then this method prints information about
	 * which handler is selected for performing this command. This does checks
	 * to see if the command is enabled and defined. If it is not both enabled
	 * and defined, then the execution listeners will be notified and an
	 * exception thrown.
	 *