001/* -*- mode: Java; c-basic-offset: 2; indent-tabs-mode: nil; coding: utf-8-unix -*- 002 * 003 * Copyright © 2017–2019 microBean. 004 * 005 * Licensed under the Apache License, Version 2.0 (the "License"); 006 * you may not use this file except in compliance with the License. 007 * You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 014 * implied. See the License for the specific language governing 015 * permissions and limitations under the License. 016 */ 017package org.microbean.configuration.spi; 018 019import java.util.Map; 020 021import java.util.concurrent.ConcurrentHashMap; 022 023import java.util.function.Function; 024 025import org.microbean.configuration.spi.AbstractResourceLoadingConfiguration.Resource; 026 027public class CachingResourceLoader<T> implements Function<Map<? extends String, ? extends String>, Resource<? extends T>> { 028 029 private final Function<? super Map<? extends String, ? extends String>, ? extends Resource<? extends T>> delegate; 030 031 private final Map<Map<? extends String, ? extends String>, Resource<? extends T>> cache; 032 033 public CachingResourceLoader(final Function<? super Map<? extends String, ? extends String>, ? extends Resource<? extends T>> delegate) { 034 super(); 035 this.delegate = delegate; 036 this.cache = delegate == null ? null : new ConcurrentHashMap<>(); 037 } 038 039 public Resource<? extends T> apply(final Map<? extends String, ? extends String> requestedConfigurationCoordinates) { 040 return this.cache == null ? null : this.cache.computeIfAbsent(requestedConfigurationCoordinates, k -> this.delegate.apply(k)); 041 } 042 043}