////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2017 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.api;
import java.util.Set;
import com.puppycrawl.tools.checkstyle.Checker;
/**
* The following interface should be implemented by each module (inheritor of
* {@link AbstractCheck}, implementor of {@link FileSetCheck}, or {@link Filter}) which uses
* external resources of any kind for its configuration. Such modules must declare external
* resource locations as a set of {@link String} which will be returned from
* {@link #getExternalResourceLocations}. This allows Checkstyle to invalidate (clear) cache
* when the content of at least one external configuration resource of the module is changed.
*
* @author Andrei Selkin
*/
public interface ExternalResourceHolder {
/**
* Returns a set of external configuration resource locations which are used by the module.
* ATTENTION!
* If 'getExternalResourceLocations()' return null, there will be
* {@link NullPointerException} in {@link Checker}.
* Such behaviour will signal that your module (check or filter) is designed incorrectly.
* It make sense to return an empty set from 'getExternalResourceLocations()'
* only for composite modules like {@link com.puppycrawl.tools.checkstyle.TreeWalker}.
* @return a set of external configuration resource locations which are used by the module.
*/
Set<String> getExternalResourceLocations();
}