I often hear complaints from users of the springframework event listener API. It seems that the vast majority of user’s end up littering their code with instanceof checks to only perform work for specific events. Something like this:
public class MyObject implements ApplicationListener {
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof MyEvent) {
//do stuff
}
}
}
Well, here’s a simple little solution that should take all that pain away.
public abstract class AbstractSpecificApplicationEventListener implements ApplicationListener {
private final Class targetClass;
public AbstractSpecificApplicationEventListener(Class targetClass) {
this.targetClass = targetClass;
}
protected abstract void onSpecificApplicationEvent(ApplicationEvent event);
public void onApplicationEvent(ApplicationEvent event) {
if (event.getClass().isAssignableFrom(targetClass)) {
onSpecificApplicationEvent(event);
}
}
}
All you need to do now is extend this class, and implement the method you want to do the work. Quite a bit cleaner!
public class MyObject extends AbstractSpecificApplicationEventListener {
public MyObject() {
super(MyEvent.class);
}
protected void onSpecificApplicationEvent(ApplicationEvent event) {
//do stuff
}
}