Question

I’m working on a Java Swing application with Google Guice as an IOC container. I’m injecting the components directly, but this let Guice create component outside EDT.

The application looks somewhat like this:

private Panel1 panel1;
private Panel2 panel2;

@Inject
public class Application(Panel1 panel1, Panel2 panel2) {
    this.panel1 = panel1;
    this.panel2 = panel2;
}

Looking at the questions here and here, I became to the conclusion of injecting a loader instead of directly a component.

private PanelLoader1 loader1;
private PanelLoader2 loader2;

private Panel1 panel1;
private Panel2 panel2;

@Inject
public class Application(PanelLoader1 loader1, PanelLoader2 loader2) {
    this.loader1 = loader1;
    this.loader2 = loader2;

    loader1.load();
    loader2.load();

    this.panel1 = loader1.get();
    this.panel2 = loader2.get();
}

public class PanelLoader {
    private Panel panel;
    public void load() {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                panel = new Panel();
            }
        });
    }
    public Panel get() {
        return panel;
    }
}

Is this correct? There is any best practice for doing that?

Answer 1

If you want to use a ‘loader’ you should implement com.google.inject.Provider. Look at the examples at http://code.google.com/p/google-guice/wiki/InjectingProviders

You don’t need to inject the providers themselves, you can configure the module to inject the objects created by the providers:

public class PanelModule extends AbstractModule {

@Override
protected void configure() {
    bind(Panel1.class).toProvider(Panel1Provider.class);
}

private static class Panel1Provider implements Provider<Panel1> {

    private Panel1 panel1;

    @Override
    public Panel1 get() {
        try {
            EventQueue.invokeAndWait(new Runnable() {
                @Override
                public void run() {
                    panel1 = new Panel1();
                }
            });
        } catch (InvocationTargetException e) {
            throw new RuntimeException(e); // should not happen
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        }
    }
    return panel1;
}

Or alternatively if you need only one instance per component you can bind directly the instances to the type:

public class PanelModule extends AbstractModule {

Panel1 panel1;
Panel2 panel2;

@Override
protected void configure() {

    try {
        EventQueue.invokeAndWait(new Runnable() {
            @Override
            public void run() {
                panel1 = new Panel1();
                panel2 = new Panel2();
            }
        });
    } catch (InvocationTargetException e) {
        throw new RuntimeException(e); // should not happen
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
    }

    bind(Panel1.class).toInstance(panel1);
    bind(Panel2.class).toInstance(panel2);
}