/*
 * Copyright 2002-2018 the original author or authors.
 *
 * 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.springframework.core.io;

import org.springframework.lang.Nullable;
import org.springframework.util.ResourceUtils;

Strategy interface for loading resources (e.. class path or file system resources). An ApplicationContext is required to provide this functionality, plus extended ResourcePatternResolver support. 
DefaultResourceLoader is a standalone implementation that is usable outside an ApplicationContext, also used by ResourceEditor. 
Bean properties of type Resource and Resource array can be populated
from Strings when running in an ApplicationContext, using the particular
context's resource loading strategy.
Author:
Juergen Hoeller
See Also:
Resource
ResourcePatternResolver
ApplicationContext
ResourceLoaderAware
Since:
10.03.2004/**
 * Strategy interface for loading resources (e.. class path or file system
 * resources). An {@link org.springframework.context.ApplicationContext}
 * is required to provide this functionality, plus extended
 * {@link org.springframework.core.io.support.ResourcePatternResolver} support.
 *
 * <p>{@link DefaultResourceLoader} is a standalone implementation that is
 * usable outside an ApplicationContext, also used by {@link ResourceEditor}.
 *
 * <p>Bean properties of type Resource and Resource array can be populated
 * from Strings when running in an ApplicationContext, using the particular
 * context's resource loading strategy.
 *
 * @author Juergen Hoeller
 * @since 10.03.2004
 * @see Resource
 * @see org.springframework.core.io.support.ResourcePatternResolver
 * @see org.springframework.context.ApplicationContext
 * @see org.springframework.context.ResourceLoaderAware
 */
public interface ResourceLoader {

	
Pseudo URL prefix for loading from the class path: "classpath:". /** Pseudo URL prefix for loading from the class path: "classpath:". */
	String CLASSPATH_URL_PREFIX = ResourceUtils.CLASSPATH_URL_PREFIX;


	
Return a Resource handle for the specified resource location.
The handle should always be a reusable resource descriptor, allowing for multiple InputStreamSource.getInputStream() calls. 

Must support fully qualified URLs, e.g. "file:C:/test.dat".
Must support classpath pseudo-URLs, e.g. "classpath:test.dat".
Should support relative file paths, e.g. "WEB-INF/test.dat".
(This will be implementation-specific, typically provided by an
ApplicationContext implementation.)

Note that a Resource handle does not imply an existing resource; you need to invoke Resource.exists to check for existence. 
Params:
location – the resource location
See Also:
CLASSPATH_URL_PREFIX
Resource.exists()
InputStreamSource.getInputStream()
Returns:
a corresponding Resource handle (never null)/**
	 * Return a Resource handle for the specified resource location.
	 * <p>The handle should always be a reusable resource descriptor,
	 * allowing for multiple {@link Resource#getInputStream()} calls.
	 * <p><ul>
	 * <li>Must support fully qualified URLs, e.g. "file:C:/test.dat".
	 * <li>Must support classpath pseudo-URLs, e.g. "classpath:test.dat".
	 * <li>Should support relative file paths, e.g. "WEB-INF/test.dat".
	 * (This will be implementation-specific, typically provided by an
	 * ApplicationContext implementation.)
	 * </ul>
	 * <p>Note that a Resource handle does not imply an existing resource;
	 * you need to invoke {@link Resource#exists} to check for existence.
	 * @param location the resource location
	 * @return a corresponding Resource handle (never {@code null})
	 * @see #CLASSPATH_URL_PREFIX
	 * @see Resource#exists()
	 * @see Resource#getInputStream()
	 */
	Resource getResource(String location);

	
Expose the ClassLoader used by this ResourceLoader.
Clients which need to access the ClassLoader directly can do so
in a uniform manner with the ResourceLoader, rather than relying
on the thread context ClassLoader.
See Also:
ClassUtils.getDefaultClassLoader()
ClassUtils.forName(String, ClassLoader)
Returns:
the ClassLoader (only null if even the system ClassLoader isn't accessible)/**
	 * Expose the ClassLoader used by this ResourceLoader.
	 * <p>Clients which need to access the ClassLoader directly can do so
	 * in a uniform manner with the ResourceLoader, rather than relying
	 * on the thread context ClassLoader.
	 * @return the ClassLoader
	 * (only {@code null} if even the system ClassLoader isn't accessible)
	 * @see org.springframework.util.ClassUtils#getDefaultClassLoader()
	 * @see org.springframework.util.ClassUtils#forName(String, ClassLoader)
	 */
	@Nullable
	ClassLoader getClassLoader();

}