apollo-client/src/main/java/com/ctrip/framework/apollo/spring/annotation/ApolloProcessor.java/ApolloProcessor/findAllField
class ApolloProcessor:  private List<Field> findAllField(Class clazz) {
    final List<Field> res = new LinkedList<>();
    ReflectionUtils.doWithFields(clazz, new ReflectionUtils.FieldCallback() {
      @Override
      public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
        res.add(field);
      }
    });
    return res;
  }