[otj-users] callins in callbacks and multiple base calls

[Marco Mosconi]

Hi Miguel,

1) To make the callin work also for the GUI thread, you have to activate 
the team for all threads (either by using 
aTeam.activate(Team.ALL_THREADS) or using the Eclipse run configuration 
tab named "Team Activation"). This is described in OTJLD §5 (global vs. 
thread-local activation).

2) For the racing issues in the output, this is because you use 
System.err in the role and System.out elsewhere. Changing to System.out 
gives the intended result.

Cheers,
Marco

Miguel Pessoa Monteiro schrieb:
> Hi everybody,
> 
> One experiment of mine gave rise to a few issues, one of which quite surprised me.
> The code below is a simplified version that illustrates them. It comprises class
> Window (extending JFrame) with a JButton in it, along an ActionListener object -
> ButtonAction - with the action for click events.
> 
> ButtonAction also has a buttonClicked method that is called from both method main
> (class Main) and method actionPerformed called by JButton from the swing thread.
> Team has a role that binds to buttonClicked.
> 
> One issue is that the callin does not seem to work when calls to buttonClicked
> originate from the swing component (and thread). It only works when buttonClicked is
> called from Main. From this, I would assume that callins are implemented in a way
> akin to AspectJ advice weaving for the call pointcut designator (PCD), as opposed to
> AspectJ's execution PCD. In AspectJ speak, we would say that callins do not work for
> events originating outside the control flow of code accessed (controlled) by the
> compiler.
> 
> Is there a way to circumvent this hurdle? Is there a way to "capture" events
> originating from code not owned by the project?
> 
> As for the surprising thing: I expected that for each message to the console from
> buttonClicked(), I would see one message from the role method appearing immediately
> after. Instead, the role seems to "accumulate" _all_ calls to buttonClicked and only
> then it sends its own messages.
> 
> I couldn't find a mention to this behaviour of callins in the language definition.
> Is it there somewhere?
> 
> Thanks,
> mpm
> 
> ===========================================================================
> import javax.swing.*;
> import java.awt.FlowLayout;
> import java.awt.event.*;
> 
> public class Window extends JFrame {
>    private static final long serialVersionUID = 0L;
> 
>    public Window(ActionListener buttonAction) {
>       super("Testing callins");
>       setLayout(new FlowLayout());
>       JButton button = new JButton("Click me");
>       button.addActionListener(buttonAction);
>       getContentPane().add(button);
> 
>       JButton quitButton = new JButton("Quit");
>       quitButton.addActionListener(
>             new ActionListener() {
>                public void actionPerformed(ActionEvent e) {
>                   System.out.println("Quiting...");
>                   System.exit(0);
>                }
>             }
>          );
>       getContentPane().add(quitButton);
>       setBounds(10, 10, 200, 100);
>       setVisible(true);
>    }
> }
> ===========================================================================
> 
> import java.awt.event.ActionListener;
> import java.awt.event.ActionEvent;
> 
> public class ButtonAction implements ActionListener {
>    public void actionPerformed(ActionEvent event) {
>       System.out.print("Click: ");
>       buttonClicked();
>    }
>    public void buttonClicked() {
>       System.out.println(getClass().getSimpleName() + " performing action.");
>    }
> }
> ===========================================================================
> 
> public team class Team {
>    public class Role playedBy ButtonAction {
>       private void react() {
>          System.err.println("JButton event occurred.");
>       }
>       react <- after buttonClicked;
>    }
> }
> ===========================================================================
> 
> public class Main {
>    public static void main(String[] args) {
>       ButtonAction buttonAction = new ButtonAction();
>       Team aTeam = new Team();
>       aTeam.activate();
>       Window window = new Window(buttonAction);
>       for(int i=0; i<10;i++) buttonAction.buttonClicked();
>    }
> }
> ===========================================================================
> 
> 

-- 
Dipl.-Inform. Marco Mosconi
Technische Universität Berlin
Fak. IV, Fachg. Softwaretechnik