001/*
002 * Copyright 2002-2019 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.core.io.support;
018
019import org.springframework.core.io.ResourceLoader;
020import org.springframework.util.ResourceUtils;
021
022/**
023 * Utility class for determining whether a given URL is a resource
024 * location that can be loaded via a {@link ResourcePatternResolver}.
025 *
026 * <p>Callers will usually assume that a location is a relative path
027 * if the {@link #isUrl(String)} method returns {@code false}.
028 *
029 * @author Juergen Hoeller
030 * @since 1.2.3
031 */
032public abstract class ResourcePatternUtils {
033
034        /**
035         * Return whether the given resource location is a URL: either a
036         * special "classpath" or "classpath*" pseudo URL or a standard URL.
037         * @param resourceLocation the location String to check
038         * @return whether the location qualifies as a URL
039         * @see ResourcePatternResolver#CLASSPATH_ALL_URL_PREFIX
040         * @see org.springframework.util.ResourceUtils#CLASSPATH_URL_PREFIX
041         * @see org.springframework.util.ResourceUtils#isUrl(String)
042         * @see java.net.URL
043         */
044        public static boolean isUrl(String resourceLocation) {
045                return (resourceLocation != null &&
046                                (resourceLocation.startsWith(ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX) ||
047                                                ResourceUtils.isUrl(resourceLocation)));
048        }
049
050        /**
051         * Return a default {@link ResourcePatternResolver} for the given {@link ResourceLoader}.
052         * <p>This might be the {@code ResourceLoader} itself, if it implements the
053         * {@code ResourcePatternResolver} extension, or a default
054         * {@link PathMatchingResourcePatternResolver} built on the given {@code ResourceLoader}.
055         * @param resourceLoader the ResourceLoader to build a pattern resolver for
056         * (may be {@code null} to indicate a default ResourceLoader)
057         * @return the ResourcePatternResolver
058         * @see PathMatchingResourcePatternResolver
059         */
060        public static ResourcePatternResolver getResourcePatternResolver(ResourceLoader resourceLoader) {
061                if (resourceLoader instanceof ResourcePatternResolver) {
062                        return (ResourcePatternResolver) resourceLoader;
063                }
064                else if (resourceLoader != null) {
065                        return new PathMatchingResourcePatternResolver(resourceLoader);
066                }
067                else {
068                        return new PathMatchingResourcePatternResolver();
069                }
070        }
071
072}