leap.lang.resource.Resource Maven / Gradle / Ivy
/*
* 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 leap.lang.resource;
import leap.lang.Charsets;
import leap.lang.exception.NestedIOException;
import leap.lang.io.InputStreamSource;
import java.io.*;
import java.net.URI;
import java.net.URL;
import java.nio.charset.Charset;
/**
* 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
*/
public interface Resource extends InputStreamSource {
/**
* Returns a new {@link InputStreamReader} wraps the {@link InputStream} returned from {@link #getInputStream()} with default charset.
*
* @throws NestedIOException if I/O error occured.
*
* @see Charsets#defaultCharset()
*/
InputStreamReader getInputStreamReader() throws NestedIOException;
/**
* Returns a new {@link InputStreamReader} wraps {@link InputStream} returned from {@link #getInputStream()} with the given charset.
*
* @throws NestedIOException if I/O error occured.
*/
InputStreamReader getInputStreamReader(Charset charset) throws NestedIOException;
/**
* Reads the content as string from the underlying {@link InputStream}.
*/
String getContent() throws NestedIOException;
/**
* Return whether this resource actually exists in physical form.
*
This method performs a definitive existence check, whereas the
* existence of a Resource handle only guarantees a
* valid descriptor handle.
*/
boolean exists();
/**
* Return whether the contents of this resource can be read,
* e.g. via {@link #getInputStream()} or {@link #getFile()}.
*
Will be true for typical resource descriptors;
* note that actual content reading may still fail when attempted.
* However, a value of false is a definitive indication
* that the resource content cannot be read.
* @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 false for typical resource descriptors.
*/
boolean isOpen();
/**
* Returns whether this resources is a {@link File}.
*/
boolean isFile();
/**
* Returns true if the resource is a directory.
*/
default boolean isDirectory() {
return isFile() && getFile().isDirectory();
}
/**
* 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;
/**
* Returns the external form of the {@link URL} returned by calling {@link #getURL()}.
*
* @throws IllegalStateException if error calling {@link #getURL()}
*/
String getURLString() throws IllegalStateException;
/**
* 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 IllegalStateException 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 NestedIOException,IllegalStateException;
/**
* Determine 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;
/**
* Determine 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;
/**
* Create a resource relative to this resource.
* @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;
/**
* Throws {@link UncheckedIOException} instead of {@link IOException}
*/
default Resource createRelativeUnchecked(String relativePath) throws UncheckedIOException {
try {
return createRelative(relativePath);
}catch (IOException e) {
throw new UncheckedIOException("Err create relative resource '" + relativePath + "'", e);
}
}
/**
* Converts this resource to {@link SimpleFileResource} if this resource is a {@link File}.
*
*
* Returns itself if this resource is {@link SimpleFileResource}.
*
* @throws IllegalStateException if not a {@link File}.
*/
FileResource toFileResource() throws IllegalStateException;
/**
* Determine a filename for this resource, i.e. typically the last
* part of the path: for example, "myfile.txt".
*
Returns null if this type of resource does not
* have a filename.
*/
String getFilename();
/**
* Returns the absolute path of the underlying {@link File}.
*
*
* Returns {@link #getURLString()} if not a {@link File}.
*/
String getFilepath() throws IllegalStateException;
/**
* Returns true if the class path is exists.
*/
default boolean hasClasspath() {
return null != getClasspath();
}
/**
* Returns the class path of this resource.
*
*
*
* Returns null if this resource is not a classpath resource.
*/
String getClasspath();
/**
* 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 toString method.
* @see java.lang.Object#toString()
*/
String getDescription();
/**
* Return the path within context or file path, or full url.
*/
default String getPath() {
if(hasClasspath()) {
return getClasspath();
}
if(isFile()) {
return getFilepath();
}
return getURLString();
}
}