001/*
002 * Copyright 2002-2016 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;
018
019import org.springframework.util.ResourceUtils;
020
021/**
022 * Strategy interface for loading resources (e.. class path or file system
023 * resources). An {@link org.springframework.context.ApplicationContext}
024 * is required to provide this functionality, plus extended
025 * {@link org.springframework.core.io.support.ResourcePatternResolver} support.
026 *
027 * <p>{@link DefaultResourceLoader} is a standalone implementation that is
028 * usable outside an ApplicationContext, also used by {@link ResourceEditor}.
029 *
030 * <p>Bean properties of type Resource and Resource array can be populated
031 * from Strings when running in an ApplicationContext, using the particular
032 * context's resource loading strategy.
033 *
034 * @author Juergen Hoeller
035 * @since 10.03.2004
036 * @see Resource
037 * @see org.springframework.core.io.support.ResourcePatternResolver
038 * @see org.springframework.context.ApplicationContext
039 * @see org.springframework.context.ResourceLoaderAware
040 */
041public interface ResourceLoader {
042
043        /** Pseudo URL prefix for loading from the class path: "classpath:" */
044        String CLASSPATH_URL_PREFIX = ResourceUtils.CLASSPATH_URL_PREFIX;
045
046
047        /**
048         * Return a Resource handle for the specified resource location.
049         * <p>The handle should always be a reusable resource descriptor,
050         * allowing for multiple {@link Resource#getInputStream()} calls.
051         * <p><ul>
052         * <li>Must support fully qualified URLs, e.g. "file:C:/test.dat".
053         * <li>Must support classpath pseudo-URLs, e.g. "classpath:test.dat".
054         * <li>Should support relative file paths, e.g. "WEB-INF/test.dat".
055         * (This will be implementation-specific, typically provided by an
056         * ApplicationContext implementation.)
057         * </ul>
058         * <p>Note that a Resource handle does not imply an existing resource;
059         * you need to invoke {@link Resource#exists} to check for existence.
060         * @param location the resource location
061         * @return a corresponding Resource handle (never {@code null})
062         * @see #CLASSPATH_URL_PREFIX
063         * @see Resource#exists()
064         * @see Resource#getInputStream()
065         */
066        Resource getResource(String location);
067
068        /**
069         * Expose the ClassLoader used by this ResourceLoader.
070         * <p>Clients which need to access the ClassLoader directly can do so
071         * in a uniform manner with the ResourceLoader, rather than relying
072         * on the thread context ClassLoader.
073         * @return the ClassLoader (only {@code null} if even the system
074         * ClassLoader isn't accessible)
075         * @see org.springframework.util.ClassUtils#getDefaultClassLoader()
076         */
077        ClassLoader getClassLoader();
078
079}