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.lang.Nullable;
021import org.springframework.util.ResourceUtils;
022
023/**
024 * Utility class for determining whether a given URL is a resource
025 * location that can be loaded via a {@link ResourcePatternResolver}.
026 *
027 * <p>Callers will usually assume that a location is a relative path
028 * if the {@link #isUrl(String)} method returns {@code false}.
029 *
030 * @author Juergen Hoeller
031 * @since 1.2.3
032 */
033public abstract class ResourcePatternUtils {
034
035        /**
036         * Return whether the given resource location is a URL: either a
037         * special "classpath" or "classpath*" pseudo URL or a standard URL.
038         * @param resourceLocation the location String to check
039         * @return whether the location qualifies as a URL
040         * @see ResourcePatternResolver#CLASSPATH_ALL_URL_PREFIX
041         * @see org.springframework.util.ResourceUtils#CLASSPATH_URL_PREFIX
042         * @see org.springframework.util.ResourceUtils#isUrl(String)
043         * @see java.net.URL
044         */
045        public static boolean isUrl(@Nullable String resourceLocation) {
046                return (resourceLocation != null &&
047                                (resourceLocation.startsWith(ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX) ||
048                                                ResourceUtils.isUrl(resourceLocation)));
049        }
050
051        /**
052         * Return a default {@link ResourcePatternResolver} for the given {@link ResourceLoader}.
053         * <p>This might be the {@code ResourceLoader} itself, if it implements the
054         * {@code ResourcePatternResolver} extension, or a default
055         * {@link PathMatchingResourcePatternResolver} built on the given {@code ResourceLoader}.
056         * @param resourceLoader the ResourceLoader to build a pattern resolver for
057         * (may be {@code null} to indicate a default ResourceLoader)
058         * @return the ResourcePatternResolver
059         * @see PathMatchingResourcePatternResolver
060         */
061        public static ResourcePatternResolver getResourcePatternResolver(@Nullable ResourceLoader resourceLoader) {
062                if (resourceLoader instanceof ResourcePatternResolver) {
063                        return (ResourcePatternResolver) resourceLoader;
064                }
065                else if (resourceLoader != null) {
066                        return new PathMatchingResourcePatternResolver(resourceLoader);
067                }
068                else {
069                        return new PathMatchingResourcePatternResolver();
070                }
071        }
072
073}