org.apache.inlong.sort.filesystem.shaded.software.amazon.ion.facet.Faceted Maven / Gradle / Ivy
/*
* Copyright 2011-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at:
*
* http://aws.amazon.com/apache2.0/
*
* or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
* language governing permissions and limitations under the License.
*/
package software.amazon.ion.facet;
/**
* Provides access to optional extension interfaces of a subject instance.
* Users can request a facet of the subject by passing the desired type token
* to {@link #asFacet(Class)}. Different implementations, or even different
* instances, of a subject may support different facets.
* Consult the subject's documentation to determine which facets are available
* in each circumstance.
*
* Design Notes
*
* Given a concrete {@link Faceted} class, it may be that some instances
* support a particular facet while others do not, depending on the state of
* the subject or the way it was constructed. In such cases
* {@link #asFacet(Class) asFacet} should choose whether to return the facet
* based on the subject's state.
* Such classes should not extend the facet
* interface (directly or indirectly), since that allows clients to bypass
* {@link #asFacet(Class) asFacet} and simply downcast the subject to the facet,
* causing problems for instances that can't support the facet.
*
* @see Facets
*
*/
public interface Faceted
{
/**
* Returns a facet of this subject if supported.
*
* @param The requested facet type.
* @param facetType The type token of the requested facet type.
*
* @return An instance of T representing the facet of the subject, or
* null if the facet is not supported by the subject.
*
* @see Facets#asFacet(Class, Faceted)
* @see Facets#assumeFacet(Class, Faceted)
*/
public T asFacet(Class facetType);
}