private static Field getAccessibleField(final Object obj, final String fieldName) {
        Validate.notNull(obj, "object can't be null");
        Validate.notBlank(fieldName, "fieldName can't be blank");
        for (Class<?> superClass = obj.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()) {
            try {
                Field field = superClass.getDeclaredField(fieldName);
                makeAccessible(field);
                return field;
            } catch (NoSuchFieldException e) {
                // Field is not defined in the current class and continues to transition up
                // new add
            }
        }
        return null;
    }
get the object's declared field.

@param obj       object
@param fieldName tje field name
@return {@linkplain Field}
shenyu-common/src/main/java/org/apache/shenyu/common/utils/ReflectUtils.java