/*
* Copyright 2018 Red Hat, Inc. and/or its affiliates
* and other contributors as indicated by the @author tags.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License 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 org.keycloak.models.cache.infinispan;
import java.util.function.Supplier;
/**
* <p>A functional interface that can be used to return data {@code D} from a source {@code S} where implementations are free to define how and when
* data is fetched from source as well how it is internally cached.
*
* <p>The source does not need to worry about caching data but always fetch data as demanded. The way data will actually be cached is an implementation detail.
*
* @author <a href="mailto:psilva@redhat.com">Pedro Igor</a>
* @see DefaultLazyLoader
*/
public interface LazyLoader<S, D> {
/**
* Returns data from the given {@code source}. Data is only fetched from {@code source} once and only if necessary, it is
* up to implementations to decide the momentum to actually fetch data from source.
*
* @param source the source from where data will be fetched.
* @return the data from source
*/
D get(Supplier<S> source);
}