/*
* Copyright 2002-2010 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.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import org.springframework.core.NestedIOException;
import org.springframework.util.ResourceUtils;
/**
* Convenience base class for {@link Resource} implementations,
* pre-implementing typical behavior.
*
* <p>The "exists" method will check whether a File or InputStream can
* be opened; "isOpen" will always return false; "getURL" and "getFile"
* throw an exception; and "toString" will return the description.
*
* @author Juergen Hoeller
* @since 28.12.2003
*/
public abstract class AbstractResource implements Resource {
/**
* This implementation checks whether a File can be opened,
* falling back to whether an InputStream can be opened.
* This will cover both directories and content resources.
*/
public boolean exists() {
// Try file existence: can we find the file in the file system?
try {
return getFile().exists();
}
catch (IOException ex) {
// Fall back to stream existence: can we open the stream?
try {
InputStream is = getInputStream();
is.close();
return true;
}
catch (Throwable isEx) {
return false;
}
}
}
/**
* This implementation always returns <code>true</code>.
*/
public boolean isReadable() {
return true;
}
/**
* This implementation always returns <code>false</code>.
*/
public boolean isOpen() {
return false;
}
/**
* This implementation throws a FileNotFoundException, assuming
* that the resource cannot be resolved to a URL.
*/
public URL getURL() throws IOException {
throw new FileNotFoundException(getDescription() + " cannot be resolved to URL");
}
/**
* This implementation builds a URI based on the URL returned
* by {@link #getURL()}.
*/
public URI getURI() throws IOException {
URL url = getURL();
try {
return ResourceUtils.toURI(url);
}
catch (URISyntaxException ex) {
throw new NestedIOException("Invalid URI [" + url + "]", ex);
}
}
/**
* This implementation throws a FileNotFoundException, assuming
* that the resource cannot be resolved to an absolute file path.
*/
public File getFile() throws IOException {
throw new FileNotFoundException(getDescription() + " cannot be resolved to absolute file path");
}
/**
* This implementation checks the timestamp of the underlying File,
* if available.
* @see #getFile()
*/
public long contentLength() throws IOException {
return getFile().length();
}
/**
* This implementation checks the timestamp of the underlying File,
* if available.
* @see #getFileForLastModifiedCheck()
*/
public long lastModified() throws IOException {
long lastModified = getFileForLastModifiedCheck().lastModified();
if (lastModified == 0L) {
throw new FileNotFoundException(getDescription() +
" cannot be resolved in the file system for resolving its last-modified timestamp");
}
return lastModified;
}
/**
* Determine the File to use for timestamp checking.
* <p>The default implementation delegates to {@link #getFile()}.
* @return the File to use for timestamp checking (never <code>null</code>)
* @throws IOException if the resource cannot be resolved as absolute
* file path, i.e. if the resource is not available in a file system
*/
protected File getFileForLastModifiedCheck() throws IOException {
return getFile();
}
/**
* This implementation throws a FileNotFoundException, assuming
* that relative resources cannot be created for this resource.
*/
public Resource createRelative(String relativePath) throws IOException {
throw new FileNotFoundException("Cannot create a relative resource for " + getDescription());
}
/**
* This implementation always throws IllegalStateException,
* assuming that the resource does not have a filename.
*/
public String getFilename() throws IllegalStateException {
throw new IllegalStateException(getDescription() + " does not have a filename");
}
/**
* This implementation returns the description of this resource.
* @see #getDescription()
*/
@Override
public String toString() {
return getDescription();
}
/**
* This implementation compares description strings.
* @see #getDescription()
*/
@Override
public boolean equals(Object obj) {
return (obj == this ||
(obj instanceof Resource && ((Resource) obj).getDescription().equals(getDescription())));
}
/**
* This implementation returns the description's hash code.
* @see #getDescription()
*/
@Override
public int hashCode() {
return getDescription().hashCode();
}
}
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