/*
* Copyright 2002-2017 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 java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import org.springframework.core.NestedIOException;
import org.springframework.util.Assert;
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.
*/
@Override
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}.
*/
@Override
public boolean isReadable() {
return true;
}
/**
* This implementation always returns {@code false}.
*/
@Override
public boolean isOpen() {
return false;
}
/**
* This implementation always returns {@code false}.
*/
@Override
public boolean isFile() {
return false;
}
/**
* This implementation throws a FileNotFoundException, assuming
* that the resource cannot be resolved to a URL.
*/
@Override
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()}.
*/
@Override
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.
*/
@Override
public File getFile() throws IOException {
throw new FileNotFoundException(getDescription() + " cannot be resolved to absolute file path");
}
/**
* This implementation returns {@link Channels#newChannel(InputStream)}
* with the result of {@link #getInputStream()}.
* <p>This is the same as in {@link Resource}'s corresponding default method
* but mirrored here for efficient JVM-level dispatching in a class hierarchy.
*/
@Override
public ReadableByteChannel readableChannel() throws IOException {
return Channels.newChannel(getInputStream());
}
/**
* This implementation reads the entire InputStream to calculate the
* content length. Subclasses will almost always be able to provide
* a more optimal version of this, e.g. checking a File length.
* @see #getInputStream()
*/
@Override
public long contentLength() throws IOException {
InputStream is = getInputStream();
Assert.state(is != null, "Resource InputStream must not be null");
try {
long size = 0;
byte[] buf = new byte[255];
int read;
while ((read = is.read(buf)) != -1) {
size += read;
}
return size;
}
finally {
try {
is.close();
}
catch (IOException ex) {
}
}
}
/**
* This implementation checks the timestamp of the underlying File,
* if available.
* @see #getFileForLastModifiedCheck()
*/
@Override
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})
* @throws FileNotFoundException if the resource cannot be resolved as
* an absolute file path, i.e. is not available in a file system
* @throws IOException in case of general resolution/reading failures
*/
protected File getFileForLastModifiedCheck() throws IOException {
return getFile();
}
/**
* This implementation throws a FileNotFoundException, assuming
* that relative resources cannot be created for this resource.
*/
@Override
public Resource createRelative(String relativePath) throws IOException {
throw new FileNotFoundException("Cannot create a relative resource for " + getDescription());
}
/**
* This implementation always returns {@code null},
* assuming that this resource type does not have a filename.
*/
@Override
public String getFilename() {
return null;
}
/**
* 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();
}
}