Java annotation to execute some code before and af

问题:

I'm writing an swing app and i'd like to have 'wait' cursor when some methods are executed. We can do it this way:

public void someMethod() {
    MainUI.getInstance().setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
    //method code
    MainUI.getInstance().setCursor(Cursor.getDefaultCursor());
}

What I'd like to achieve is a java annotation, that would set wait cursor before method execution and set it back to normal after execution. So previous example would look something like this

@WaitCursor    
public void someMethod() {
    //method code
}

How can i achieve this? Suggestions about other variants of solving this problem are also welcome. Thanks!

P.S. - We use Google Guice in our project, but i don't get how to solve the problem using it. If someone would provide me with simple example of similar problem, that would be very helpful

回答1:

You may use AspectJ, or use Google Guice which bring its own AOP.

The object having the method annotated with your WaitCursor annotation must be injected with Guice.

You define your annotation

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface WaitCursor {}

You add a MethodInterceptor :

public class WaitCursorInterceptor implements MethodInterceptor {
    public Object invoke(MethodInvocation invocation) throws Throwable {
        // show the cursor
        MainUI.getInstance().setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
        // execute the method annotated with `@WaitCursor`
        Object result = invocation.proceed();
        // hide the waiting cursor
        MainUI.getInstance().setCursor(Cursor.getDefaultCursor());
        return result;
    }
}

And define a module where you bind the interceptor on any method having your annotation.

public class WaitCursorModule extends AbstractModule {
    protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.annotatedWith(WaitCursor.class), new WaitCursorInterceptor());
    }
}

You can see more advanced uses on this page

回答2:

You might want to look at using around() advice in AspectJ in conjunction with your annotation to associate the around() advice with all methods that are qualified with your annotation.