Spring Dependency Injection not working correctly

Question

I have a Spring/Swing application in which I'm experimenting DI but whatever I've done so far, I couldn't make it work properly. Here are some example classes I work on;

public class Launcher {

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            public void run() {
                ApplicationContext context = null;
                try {
                    context = new AnnotationConfigApplicationContext(AppConfig.class);
                    MainFrame mainFrame = (MainFrame) context.getBean("mainFrame");
                    mainFrame.init();
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (context != null)
                        ((ConfigurableApplicationContext) context).close();
                }
            }
        });

    }

}


@Configuration
@ComponentScan("tr.com.example.*")
public class AppConfig {

    @Bean(name = "mainFrame")
    public MainFrame createMainFrame() {
        return new MainFrame();
    }
}


public class MyPanel{

    @Autowired
    MyManager manager;

    ...do stuff
}


@Service
public class MyManager{
    ...do stuff
}

So, when I try to inject MyManager to MyPanel, I'm getting NullPointerException. But if I try to inject it to MainFrame it works.

Can someone please explain me what's wrong here and how should I make it correctly?

Thanks in advance.

Answer 1

It is not working beacuse you have not use @Component over MyPanel

public class Launcher {

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            public void run() {
                ApplicationContext context = null;
                try {
                    context = new AnnotationConfigApplicationContext(AppConfig.class);
                    MainFrame mainFrame = (MainFrame) context.getBean("mainFrame");
                    mainFrame.init();
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (context != null)
                        ((ConfigurableApplicationContext) context).close();
                }
            }
        });

    }

}


@Configuration
@ComponentScan("tr.com.example.*")
public class AppConfig {

    @Bean(name = "mainFrame")
    public MainFrame createMainFrame() {
        return new MainFrame();
    }
}

@Component
public class MyPanel{

    @Autowired
    MyManager manager;

    ...do stuff
}


@Service
public class MyManager{
    ...do stuff
}

Answer 2

Your MyPanel is not a @Component, therefore it's invisible to Spring and any @Autowired or other annotations won't be processed.

The key to Spring is to use it fully. Unless you know that something shouldn't be a bean (i.e. a domain class, entity or so on) it probably should be a bean.