AnnotationAwareOrderComparator类分析

解析

类继承了OrderComparator

public class AnnotationAwareOrderComparator extends OrderComparator {
}

• 属性就一个，该对象的实例

  //public static final AnnotationAwareOrderComparator INSTANCE = new AnnotationAwareOrderComparator();
  public static final AnnotationAwareOrderComparator INSTANCE = new AnnotationAwareOrderComparator();

• 剩下的都是静态方法
  这个方法的每一行都比较清晰。通过这个方法能学到不少东西：
  1、对于类，我们能通过OrderUtils.getOrder((Class<?>) obj)获取
  2、对于注解类型，我们能通过AnnotationUtils.getAnnotation来获取注解内容。
  3、方法，我们通过AnnotationUtils.findAnnotation((Method) obj, Order.class);获取。大家可以自行实验下。

  @Override
      @Nullable
      protected Integer findOrder(Object obj) {
          // Check for regular Ordered interface
          Integer order = super.findOrder(obj);
          if (order != null) {
              return order;
          }
  
          // Check for @Order and @Priority on various kinds of elements
          if (obj instanceof Class) {
              return OrderUtils.getOrder((Class<?>) obj);
          }
          else if (obj instanceof Method) {
              Order ann = AnnotationUtils.findAnnotation((Method) obj, Order.class);
              if (ann != null) {
                  return ann.value();
              }
          }
          else if (obj instanceof AnnotatedElement) {
              Order ann = AnnotationUtils.getAnnotation((AnnotatedElement) obj, Order.class);
              if (ann != null) {
                  return ann.value();
              }
          }
          else {
              order = OrderUtils.getOrder(obj.getClass());
              if (order == null && obj instanceof DecoratingProxy) {
                  order = OrderUtils.getOrder(((DecoratingProxy) obj).getDecoratedClass());
              }
          }
  
          return order;
      }