AnnotationUtil.java 文件源码

/**
 * Execute the supplied runnable once (in same thread) if the supplied method has the supplied annotation.
 * This method supports inheritance of method annotations. If the supplied method overrides a superclass or
 * implements an interface with the annotation the runnable will be executed. Even if the annotation is available
 * from multiple levels of the class hierarchy the runnable will only execute once.
 *
 * @param meth         The method to test
 * @param r            The runnable that will run depending on the annotation
 * @param runIfPresent true to run when the annotation is found, false to run when it's not found.
 * @param annotation   The annotation we are looking for
 */
public void runIfMethodAnnotated(Method meth, Runnable r, boolean runIfPresent,
                                 Class<? extends Annotation> annotation) {
  if (!annotation.isAnnotationPresent(Inherited.class)) {
    boolean annotationPresent = meth.isAnnotationPresent(annotation);
    if (runIfPresent && annotationPresent || !runIfPresent && !annotationPresent) {
      r.run();
    }
  } else {
    Set<Class> classes = new HashSet<>();
    Class<?> clazz = meth.getDeclaringClass();
    collectInterfaces(classes, clazz);
    while (clazz != Object.class) {
      classes.add(clazz);
      clazz = clazz.getSuperclass();
    }

    // now iterate all superclasses and interfaces looking for a method with identical signature that has 
    // the annotation in question.
    boolean found = false;
    for (Class<?> c : classes) {
      try {
        Method m = c.getMethod(meth.getName(), meth.getParameterTypes());
        Annotation[] declaredAnnotations = m.getDeclaredAnnotations();
        for (Annotation a : declaredAnnotations) {
          found |= annotation == a.annotationType();
          if (runIfPresent && found) {
            r.run();
            return;
          }
        }
      } catch (NoSuchMethodException ignored) {
      }
    }
    if (!runIfPresent && !found) {
      r.run();
    }
  }
}