/*
* Copyright 2002-2016 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 java.net.MalformedURLException;
import java.net.URL;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;
/**
* Default implementation of the {@link ResourceLoader} interface.
* Used by {@link ResourceEditor}, and serves as base class for
* {@link org.springframework.context.support.AbstractApplicationContext}.
* Can also be used standalone.
*
* <p>Will return a {@link UrlResource} if the location value is a URL,
* and a {@link ClassPathResource} if it is a non-URL path or a
* "classpath:" pseudo-URL.
*
* @author Juergen Hoeller
* @since 10.03.2004
* @see FileSystemResourceLoader
* @see org.springframework.context.support.ClassPathXmlApplicationContext
*/
public class DefaultResourceLoader implements ResourceLoader {
private ClassLoader classLoader;
private final Set<ProtocolResolver> protocolResolvers = new LinkedHashSet<>(4);
private final Map<Class<?>, Map<Resource, ?>> resourceCaches = new ConcurrentHashMap<>(4);
/**
* Create a new DefaultResourceLoader.
* <p>ClassLoader access will happen using the thread context class loader
* at the time of this ResourceLoader's initialization.
* @see java.lang.Thread#getContextClassLoader()
*/
public DefaultResourceLoader() {
this.classLoader = ClassUtils.getDefaultClassLoader();
}
/**
* Create a new DefaultResourceLoader.
* @param classLoader the ClassLoader to load class path resources with, or {@code null}
* for using the thread context class loader at the time of actual resource access
*/
public DefaultResourceLoader(ClassLoader classLoader) {
this.classLoader = classLoader;
}
/**
* Specify the ClassLoader to load class path resources with, or {@code null}
* for using the thread context class loader at the time of actual resource access.
* <p>The default is that ClassLoader access will happen using the thread context
* class loader at the time of this ResourceLoader's initialization.
*/
public void setClassLoader(ClassLoader classLoader) {
this.classLoader = classLoader;
}
/**
* Return the ClassLoader to load class path resources with.
* <p>Will get passed to ClassPathResource's constructor for all
* ClassPathResource objects created by this resource loader.
* @see ClassPathResource
*/
@Override
public ClassLoader getClassLoader() {
return (this.classLoader != null ? this.classLoader : ClassUtils.getDefaultClassLoader());
}
/**
* Register the given resolver with this resource loader, allowing for
* additional protocols to be handled.
* <p>Any such resolver will be invoked ahead of this loader's standard
* resolution rules. It may therefore also override any default rules.
* @since 4.3
* @see #getProtocolResolvers()
*/
public void addProtocolResolver(ProtocolResolver resolver) {
Assert.notNull(resolver, "ProtocolResolver must not be null");
this.protocolResolvers.add(resolver);
}
/**
* Return the collection of currently registered protocol resolvers,
* allowing for introspection as well as modification.
* @since 4.3
*/
public Collection<ProtocolResolver> getProtocolResolvers() {
return this.protocolResolvers;
}
/**
* Obtain a cache for the given value type, keyed by {@link Resource}.
* @param valueType the value type, e.g. an ASM {@code MetadataReader}
* @return the cache {@link Map}, shared at the {@code ResourceLoader} level
* @since 5.0
*/
@SuppressWarnings("unchecked")
public <T> Map<Resource, T> getResourceCache(Class<T> valueType) {
return (Map<Resource, T>) this.resourceCaches.computeIfAbsent(valueType, key -> new ConcurrentHashMap<>());
}
/**
* Clear all resource caches in this resource loader.
* @since 5.0
* @see #getResourceCache
*/
public void clearResourceCaches() {
this.resourceCaches.clear();
}
@Override
public Resource getResource(String location) {
Assert.notNull(location, "Location must not be null");
for (ProtocolResolver protocolResolver : this.protocolResolvers) {
Resource resource = protocolResolver.resolve(location, this);
if (resource != null) {
return resource;
}
}
if (location.startsWith("/")) {
return getResourceByPath(location);
}
else if (location.startsWith(CLASSPATH_URL_PREFIX)) {
return new ClassPathResource(location.substring(CLASSPATH_URL_PREFIX.length()), getClassLoader());
}
else {
try {
// Try to parse the location as a URL...
URL url = new URL(location);
return new UrlResource(url);
}
catch (MalformedURLException ex) {
// No URL -> resolve as resource path.
return getResourceByPath(location);
}
}
}
/**
* Return a Resource handle for the resource at the given path.
* <p>The default implementation supports class path locations. This should
* be appropriate for standalone implementations but can be overridden,
* e.g. for implementations targeted at a Servlet container.
* @param path the path to the resource
* @return the corresponding Resource handle
* @see ClassPathResource
* @see org.springframework.context.support.FileSystemXmlApplicationContext#getResourceByPath
* @see org.springframework.web.context.support.XmlWebApplicationContext#getResourceByPath
*/
protected Resource getResourceByPath(String path) {
return new ClassPathContextResource(path, getClassLoader());
}
/**
* ClassPathResource that explicitly expresses a context-relative path
* through implementing the ContextResource interface.
*/
protected static class ClassPathContextResource extends ClassPathResource implements ContextResource {
public ClassPathContextResource(String path, ClassLoader classLoader) {
super(path, classLoader);
}
@Override
public String getPathWithinContext() {
return getPath();
}
@Override
public Resource createRelative(String relativePath) {
String pathToUse = StringUtils.applyRelativePath(getPath(), relativePath);
return new ClassPathContextResource(pathToUse, getClassLoader());
}
}
}