com.automationrockstars.gunter.events.DecoratorFinder Maven / Gradle / Ivy

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package com.automationrockstars.gunter.events;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;

import eu.infomas.annotation.AnnotationDetector;
import eu.infomas.annotation.AnnotationDetector.MethodReporter;

public class DecoratorFinder {

	private static List decorators = Lists.newArrayList();
	private static Logger LOG = LoggerFactory.getLogger(DecoratorFinder.class);
	static {
		AnnotationDetector detector = new AnnotationDetector(new DecoratorReporter());
		try {
			detector.detect();
		} catch (IOException e) {
			LOG.error("Cannot execute detection for {}",DecoratorFinder.class);
		}
	}
	
	public static Event decorate(Event event){
		for (Method decorator : decorators){
			try {
				event = (Event) decorator.invoke(null, event);
			} catch (Throwable e) {
				LOG.error("Decorator {} failed on event {}",decorator,event);
			}
		}
		return event;
	}
	
	public static class DecoratorReporter implements MethodReporter {

		@SuppressWarnings("unchecked")
		@Override
		public Class[] annotations() {
			return new Class[] {EventDecorator.class};
		}

		@Override
		public void reportMethodAnnotation(Class annotation, String className,
				String methodName) {
			try {
				for (Method method : Class.forName(className).getMethods()){
					Preconditions.checkArgument(Modifier.isStatic(method.getModifiers()) && Modifier.isPublic(method.getModifiers()),"Decorator method needs to be public static");
					Preconditions.checkArgument(Event.class.isAssignableFrom(method.getReturnType()),"Decorator method needs to return TestEvent");
					Preconditions.checkArgument(method.getParameterTypes().length == 1 && Event.class.isAssignableFrom(method.getParameterTypes()[0]),"Decorator method needs to accept one argument of type TestEvent");
					decorators.add(method);
				}
			} catch (SecurityException | ClassNotFoundException | IllegalArgumentException e) {
				LOG.error("Cannot use decorator method {} due to {}",methodName,e.toString());
			}
			
		}
		
	}
}