如何等待反射线程完成

Question

I have an application class which allows the user to download a jar file, this jar file is then accessed using reflection.

public void install() {
    File app = new File("C:/Temp/" + this.name + ".jar");
    if(!app.exists())
        download();

    URLClassLoader appLoader;
    Class<?> appBuilder = null;

    try {
        appLoader = URLClassLoader.newInstance(new URL[] { new URL("C:/Temp/" + this.name + ".jar") });
        appBuilder = appLoader.loadClass("iezon.app.App");
    } catch (MalformedURLException | ClassNotFoundException e) {
        WebSocket.addError(e);
    }

    this.application = appBuilder;
}

private void download() {
    try {
        FileUtils.copyURLToFile(new URL(this.downloadUrl), new File("C:/Temp/" + this.name + ".jar"));
    } catch (IOException e) {
        WebSocket.addError(e);
    }
}

Here, I am creating a new instance of the jar file:

public void start() {
    try {
        App.createWindow(this.application.getClass());
    } catch (InstantiationException | IllegalAccessException e) {
        WebSocket.addError(e);
    }
}

Window is custom extension of a JFrame that is used as a base template for GUI design.

public static int createWindow(Class<?> window) throws InstantiationException, IllegalAccessException {
    factory.add((Window) window.newInstance());
    factory.get(factory.size() - 1).windowId = factory.size() - 1;
    factory.get(factory.size() - 1).run();
    return factory.size() - 1;
}

Since the jar file, once instanced, cannot access this code to load the home screen window on exit, I was wondering how I can wait for the jar file instance to be closed and then relaunch the home screen:

ie in suedo code:

when (create App.createWindow(this.application.getClass()))
dies
create App.createWindow(HomeScreen.class)

Is there a way I can use wait() and notify() methods? Or possibly add a listener when instancing the Class like factory.get(factory.size() - 1).addSomeExitListener.....() ?

Answer 1

You can forget about the reflection part, it's not really relevant since the same would be true if you were given a regularly constructed instance.

You'll need to design your Window class in a way that it works as desired, eg let it callback you when it's done. Since it is a JFrame you could also use it's window close listener like:

public static int createWindow(Class<?> window) throws InstantiationException, IllegalAccessException {
    Window instance = (Window) window.newInstance();
    factory.add(instance);
    instance.windowId = factory.size() - 1;
    if (window != HomeScreen.class) {
        // instance.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); // ?
        instance.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosed(WindowEvent e) {
                App.createWindow(HomeScreen.class);
            }
        });
    }
    instance.run();
    return factory.size() - 1;
}