org.scijava.command

Class ContextCommand

java.lang.Object

org.scijava.AbstractContextual

org.scijava.command.ContextCommand

All Implemented Interfaces:

Runnable, Cancelable, Command, Contextual, SciJavaPlugin

Direct Known Subclasses:

UnimplementedCommand

public abstract class ContextCommand
extends AbstractContextual
implements Cancelable, Command

A command that knows its context. Its service parameters are automatically populated when AbstractContextual.setContext(org.scijava.Context) is called, to make it easier to use via Java API calls (i.e., without invoking it via CommandService.run(java.lang.String, boolean, java.lang.Object...)). This improves compile-time safety of downstream code that calls the command.

Here is an example command execution using CommandService.run(java.lang.String, boolean, java.lang.Object...):

Future<CommandModule<FindEdges>> future =<br/> commandService.run(findEdges.class, "display", myDisplay);<br/> CommandModule<FindEdges> module = future.get(); // block till complete<br/> ImageDisplay outDisplay = (ImageDisplay) module.getOutput("display");

Note that FindEdges also has two other inputs, an ImageDisplayService and an OverlayService, which get automatically populated when the application context is injected.

Here is the same command execution via direct Java calls:

FindEdges findEdges = new FindEdges();<br/> findEdges.setContext(context); // populates service parameters<br/> findEdges.setDisplay(myDisplay);<br/> findEdges.run(); // execute on the same thread<br/> ImageDisplay outDisplay = findEdges.getDisplay();

We believe the latter is more intuitive for most Java programmers, and so encourage commands to extend this class and provide API to use them directly.

That said, there are times when you cannot extend a particular class (usually because you must extend a different class instead). In that case, you can still implement the Command interface and end up with a perfectly serviceable command. The consequence is only that other Java programmers will not be able to use the latter paradigm above to invoke your code in a fully compile-time-safe way.

Author:

Curtis Rueden

Constructor Summary

Constructors

Constructor and Description
ContextCommand()

Method Summary

Methods

Modifier and Type	Method and Description
void	cancel(String reason) Cancels the command execution, with the given reason for doing so.
String	getCancelReason() Gets a message describing why the operation was canceled.
boolean	isCanceled() Gets whether the operation has been canceled.

Methods inherited from class org.scijava.AbstractContextual

context, getContext, setContext

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Runnable

run

Constructor Detail

ContextCommand

public ContextCommand()

Method Detail

isCanceled

public boolean isCanceled()

Description copied from interface: Cancelable

Gets whether the operation has been canceled.

Specified by:

isCanceled in interface Cancelable

cancel

public void cancel(String reason)

Cancels the command execution, with the given reason for doing so.

Specified by:

cancel in interface Cancelable

Parameters:

reason - A message describing why the operation is being canceled.

getCancelReason

public String getCancelReason()

Description copied from interface: Cancelable

Gets a message describing why the operation was canceled.

Specified by:

getCancelReason in interface Cancelable

Returns:

The reason for cancelation, which may be null if no reason was given, or if the operation was not in fact canceled.