What does beanInterface refer here?

public class SpringHelloWorld extends com.itmill.toolkit.Application {

    public void init() {
        final Window main = new Window("Hello window");
        setMainWindow(main);

        SpringContextHelper helper = new SpringContextHelper(this);
        MyBeanInterface bean = (MyBeanInterface) 
           开发者_JAVA技巧     helper.getBean("myBean");
        main.addComponent(new Label( bean.myMethod() ));
    }
}

http://qastegiano.blogspot.com/2008/01/itmill-toolkit-5-spring.html

Is it a custom class or we should define something out there.

You've got to define something out there. It's an example of how to get a bean out of the bean factory; substitute a useful class of your own.