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/*
* Copyright 2002-2012 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 spark.resource;
import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URL;
/**
* Interface for a resource descriptor that abstracts from the actual
* type of underlying resource, such as a file or class path resource.
* An InputStream can be opened for every resource if it exists in
* physical form, but a URL or File handle can just be returned for
* certain resources. The actual behavior is implementation-specific.
*
* @author Juergen Hoeller
* @see #getInputStream()
* @see #getURL()
* @see #getURI()
* @see #getFile()
* @see ClassPathResource
* @see InputStreamResource
* Code copied from Spring source. Modifications made (mostly removal of methods) by Per Wendel.
*/
public interface Resource extends InputStreamResource {
/**
* Return whether this resource actually exists in physical form.
*
This method performs a definitive existence check, whereas the
* existence of a {@code Resource} handle only guarantees a
* valid descriptor handle.
*
* @return if exists
*/
boolean exists();
/**
* Return whether the contents of this resource can be read,
* e.g. via {@link #getInputStream()} or {@link #getFile()}.
*
Will be {@code true} for typical resource descriptors;
* note that actual content reading may still fail when attempted.
* However, a value of {@code false} is a definitive indication
* that the resource content cannot be read.
*
* @return if readable
* @see #getInputStream()
*/
boolean isReadable();
/**
* Return whether this resource represents a handle with an open
* stream. If true, the InputStream cannot be read multiple times,
* and must be read and closed to avoid resource leaks.
*
Will be {@code false} for typical resource descriptors.
*
* @return if open
*/
boolean isOpen();
/**
* @return a URL handle for this resource.
* @throws IOException if the resource cannot be resolved as URL,
* i.e. if the resource is not available as descriptor
*/
URL getURL() throws IOException;
/**
* @return a URI handle for this resource.
* @throws IOException if the resource cannot be resolved as URI,
* i.e. if the resource is not available as descriptor
*/
URI getURI() throws IOException;
/**
* @return a File handle for this resource.
* @throws IOException if the resource cannot be resolved as absolute
* file path, i.e. if the resource is not available in a file system
*/
File getFile() throws IOException;
/**
* @return the content length for this resource.
* @throws IOException if the resource cannot be resolved
* (in the file system or as some other known physical resource type)
*/
long contentLength() throws IOException;
/**
* @return the last-modified timestamp for this resource.
* @throws IOException if the resource cannot be resolved
* (in the file system or as some other known physical resource type)
*/
long lastModified() throws IOException;
/**
* @param relativePath the relative path (relative to this resource)
* @return the resource handle for the relative resource
* @throws IOException if the relative resource cannot be determined
*/
Resource createRelative(String relativePath) throws IOException;
/**
* Determine a filename for this resource, i.e. typically the last
* part of the path: for example, "myfile.txt".
*
Returns {@code null} if this type of resource does not
* have a filename.
*
* @return the file name.
*/
String getFilename();
/**
* @return a description for this resource,
* to be used for error output when working with the resource.
*
Implementations are also encouraged to return this value
* from their {@code toString} method.
* @see Object#toString()
*/
String getDescription();
}