First, the “Select All” action should be similar to other eclipse standard actions, like “Undo” and “Delete”, so I expected some treatment similar to these actions – a SelectAllRetargetAction or something similar. There is a SelectAllAction class in the GEF framework, but I was not sure how to plug it in. First, I saw that this action was already registered in the actionRegistry in GraphicalEditor.createActions() function. So why was it disabled? More code reading showed me that also the undo and redo actions are registered there, but I also had to create for them a retargetable action in the ActionBarContributor of my editor. So I added this code to the OPMGraphicalEditorActionBarContributor.buildActions() method (the last line):

	@Override
	protected void buildActions() {
		addRetargetAction(new UndoRetargetAction());
		addRetargetAction(new RedoRetargetAction());
		addRetargetAction(new DeleteRetargetAction());
		addRetargetAction(new RetargetAction(GEFActionConstants.TOGGLE_GRID_VISIBILITY,
				GEFMessages.ToggleGrid_Label,
				IAction.AS_CHECK_BOX));
		addRetargetAction(new RetargetAction(GEFActionConstants.TOGGLE_SNAP_TO_GEOMETRY,
				GEFMessages.ToggleSnapToGeometry_Label,
				IAction.AS_CHECK_BOX));
		addRetargetAction(new RetargetAction(GEFActionConstants.SELECT_ALL, GEFMessages.SelectAllAction_Label));
	}

The “Select All” menu item became available and the action worked, even with the expected “Ctrl+A” keyboard accelerator. But the editor showed me that the GEFActionConstants.SELECT_ALL constant is deprecated, and that I should use the ActionFactory.SELECT_ALL.getId()… I scratched my head a bit… I had a new lead on my problem, but where to search for clues? Obviously, the org.eclipse.gef.examples.logic project! And there it was: the ActionBarContributor.declareGlobalActionKeys() function calls addGlobalActionKey(ActionFactory.SELECT_ALL.getId()). In two minutes I removed my old line and added this one to my contributor class, and there it was again, the “Select All” action worked, and the code was clean of warnings.

Seems strange to me that although the action was already registered, only when I added here the action became available. The name of the function (and it’s location) is also confusing: why the Bar in ActionBarContributor? And another nice thing in the code of this class is the warning in the class comment:

/**
 * Contributes actions to the workbench. !!Warning: This class is subject to
 * change.
 */

But the “Select All” action works, and that is what matters.

Related posts:

1. Creating a GEF Editor – Part 12: Enable Save Action on the Editor
2. Creating an OPM GEF Editor – Part 18: Snapping to Grid and to Geometry
3. Creating a GEF Editor – Part 8: Delete, Undo and Redo

Some thoughts on my implementation:

First, I do no parameter validation or error checking. So what can happen? here are a few examples:

• The input file may not exist.
• The input file exists but is not a zip file.
• The output directory does not exist.
• Problems may occur in the middle of the process of reading from the input file or writing to the file system (for example if your output file system is a network disk and your cat just ate the network cable).

As you can see, many things can go wrong (and will), so a GOOD implementation (not a simple example) should check for these problems and deal with them as best as it can. I personally don’t like the way Java forces you to catch all exceptions, because it makes code harder to read. But in real systems you cannot have this luxury.

Second, the implementation assumes that the Enumeration returned by the ZipFile is ordered – directories before the files in the directories. I didn’t find any comments about this in the documentation of ZipFile… maybe it’s part of the zip standard.

Related posts:

1. Java Examples Repository – First Example: Copy a File from a URL to a Local Path
2. Creating a GEF Editor – Part 5: Loading the Model from an EMF File
3. The Quest for the Perfect Java Graph Framework

/*******************************************************************************
 * Copyright (c) 2012 Arieh 'Vainolo' Bibliowicz
 * You can use this code for educational purposes. For any other uses
 * please contact me: vainolo@gmail.com
 *******************************************************************************/
package com.vainolo.examples.net;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.net.URL;
import java.net.URLConnection;

public class NetworkFileCopier {
	public static File copyFileFromWeb(String address, String filePath) throws Exception {
		byte[] buffer = new byte[1024];
		int bytesRead;

		URL url = new URL(address);
		BufferedInputStream inputStream = null;
		BufferedOutputStream outputStream = null;
		URLConnection connection = url.openConnection();
		// If you need to use a proxy for your connection, the URL class has another openConnection method.
		// For example, to connect to my local SOCKS proxy I can use:
		// url.openConnection(new Proxy(Proxy.Type.SOCKS, newInetSocketAddress("localhost", 5555)));
		inputStream = new BufferedInputStream(connection.getInputStream());
		File f = new File(filePath);
		outputStream = new BufferedOutputStream(new FileOutputStream(f));
		while ((bytesRead = inputStream.read(buffer)) != -1) {
			outputStream.write(buffer, 0, bytesRead);
		}
		inputStream.close();
		outputStream.close();
		return f;
	}
}

The code is available on the Vainosamples repository. Oh, and if you have a better implementation, please do tell me!

Related posts:

1. Learning JUNG – Java Universal Network/Graph Framework
2. JGraph – Another Java Graph Framework
3. Creating a GEF Editor – Part 5: Loading the Model from an EMF File

In its most simplest form, a factory method simply replaces the constructor:

And we can show how this works using a sequence diagram:

We can obviously add more functionality to the createProduct() method, but this is trivial. A more complex example is to use polymorphism to get factories that can create different kinds of objects, all of which comply to the same abstraction. This is how it is described by the GOF (fairly overlapping the abstract factory pattern):

This implementation completely decouples the client from the implementation. The client is only aware of a Creator and an Abstraction with complete disregard of their implementations. The creator is somehow available to the client (via dependency injection). So now that we have a static model, is there a way to describe the dynamics of this diagram using a sequence diagram? Let’s try:

It turns out that to model the flow of operations I am actually modeling how polymorphism, late binding and all that stuff works. I guess that in this case, a sequence diagram is not only irrelevant, but actually confusing. But I had to try

Related posts:

1. Singleton Design Pattern – Sequence Diagram

Keyboard shortcuts are very useful for activating actions. There are many shortcuts that are common in all environments – and for better usability, enabling this shortcuts give the user a better user experience. In my case, I wanted to let the user edit the name of a thing (or state) using the F2 key, which is commonly used for this purpose.

Adding keyboard shortcuts to GEF is fairly easy. You only need to define a <code>KeyHandler</code> and attach it to the graphical viewer. I defined two key shortcuts: F2 for direct editing, and F3 for my own ResizeToContentsAction action.

	private void configureKeyboardShortcuts() {
		getGraphicalViewer().getKeyHandler();<br> GraphicalViewerKeyHandler keyHandler = new GraphicalViewerKeyHandler(getGraphicalViewer())
		keyHandler.put(KeyStroke.getPressed(SWT.F2, 0), getActionRegistry().getAction(GEFActionConstants.DIRECT_EDIT));
		keyHandler.put(KeyStroke.getPressed(SWT.F3, 0),
				getActionRegistry().getAction(ResizeToContentsAction.RESIZE_TO_CONTENTS_ID));
		getGraphicalViewer().setKeyHandler(keyHandler);
	}

This function is called from the configureGraphicalViewer. And that is all! You can find the source for this change in my github repository: https://github.com/vainolo/Object-Process-Programming.

Related posts:

1. Creating an OPM GEF Editor – Part 20: Creating a Context Menu and Adding Custom Actions
2. Creating an OPM GEF Editor – Part 18: Snapping to Grid and to Geometry
3. Creating an OPM GEF Editor – Part 15: Adding Structural Links