/*
 * Copyright 2002-2020 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
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
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 * 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
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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.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.NestedIOException;
import org.springframework.lang.Nullable;
import org.springframework.util.ResourceUtils;

Convenience base class for Resource implementations, pre-implementing typical behavior.

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, Sam Brannen
Since:28.12.2003
/** * 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 * @author Sam Brannen * @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.
/** * 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? if (isFile()) { try { return getFile().exists(); } catch (IOException ex) { Log logger = LogFactory.getLog(getClass()); if (logger.isDebugEnabled()) { logger.debug("Could not retrieve File for existence check of " + getDescription(), ex); } } } // Fall back to stream existence: can we open the stream? try { getInputStream().close(); return true; } catch (Throwable ex) { Log logger = LogFactory.getLog(getClass()); if (logger.isDebugEnabled()) { logger.debug("Could not retrieve InputStream for existence check of " + getDescription(), ex); } return false; } }
This implementation always returns true for a resource that exists (revised as of 5.1).
/** * This implementation always returns {@code true} for a resource * that {@link #exists() exists} (revised as of 5.1). */
@Override public boolean isReadable() { return exists(); }
This implementation always returns false.
/** * This implementation always returns {@code false}. */
@Override public boolean isOpen() { return false; }
This implementation always returns 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.
/** * 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 getURL().
/** * 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.
/** * 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 Channels.newChannel(InputStream) with the result of InputStreamSource.getInputStream().

This is the same as in Resource's corresponding default method but mirrored here for efficient JVM-level dispatching in a class hierarchy.

/** * 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 method reads the entire InputStream to determine the content length.

For a custom sub-class of InputStreamResource, we strongly recommend overriding this method with a more optimal implementation, e.g. checking File length, or possibly simply returning -1 if the stream can only be read once.

See Also:
/** * This method reads the entire InputStream to determine the content length. * <p>For a custom sub-class of {@code InputStreamResource}, we strongly * recommend overriding this method with a more optimal implementation, e.g. * checking File length, or possibly simply returning -1 if the stream can * only be read once. * @see #getInputStream() */
@Override public long contentLength() throws IOException { InputStream is = getInputStream(); try { long size = 0; byte[] buf = new byte[256]; int read; while ((read = is.read(buf)) != -1) { size += read; } return size; } finally { try { is.close(); } catch (IOException ex) { Log logger = LogFactory.getLog(getClass()); if (logger.isDebugEnabled()) { logger.debug("Could not close content-length InputStream for " + getDescription(), ex); } } } }
This implementation checks the timestamp of the underlying File, if available.
See Also:
  • getFileForLastModifiedCheck()
/** * This implementation checks the timestamp of the underlying File, * if available. * @see #getFileForLastModifiedCheck() */
@Override public long lastModified() throws IOException { File fileToCheck = getFileForLastModifiedCheck(); long lastModified = fileToCheck.lastModified(); if (lastModified == 0L && !fileToCheck.exists()) { throw new FileNotFoundException(getDescription() + " cannot be resolved in the file system for checking its last-modified timestamp"); } return lastModified; }
Determine the File to use for timestamp checking.

The default implementation delegates to getFile().

Throws:
  • FileNotFoundException – if the resource cannot be resolved as an absolute file path, i.e. is not available in a file system
  • IOException – in case of general resolution/reading failures
Returns:the File to use for timestamp checking (never null)
/** * 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.
/** * 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 null, assuming that this resource type does not have a filename.
/** * This implementation always returns {@code null}, * assuming that this resource type does not have a filename. */
@Override @Nullable public String getFilename() { return null; }
This implementation compares description strings.
See Also:
  • getDescription()
/** * This implementation compares description strings. * @see #getDescription() */
@Override public boolean equals(@Nullable Object other) { return (this == other || (other instanceof Resource && ((Resource) other).getDescription().equals(getDescription()))); }
This implementation returns the description's hash code.
See Also:
  • getDescription()
/** * This implementation returns the description's hash code. * @see #getDescription() */
@Override public int hashCode() { return getDescription().hashCode(); }
This implementation returns the description of this resource.
See Also:
  • getDescription()
/** * This implementation returns the description of this resource. * @see #getDescription() */
@Override public String toString() { return getDescription(); } }