AbstractResource.java

package jef.tools.resource;

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 jef.tools.ResourceUtils;

public abstract class AbstractResource implements IResource {

	/**
	 * 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(){
		throw new UnsupportedOperationException(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 IOException("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 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()
	 */
	public long contentLength() throws IOException {
		InputStream is = getInputStream();
		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()
	 */
	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 IResource createRelative(String relativePath) throws IOException {
		throw new FileNotFoundException("Cannot create a relative resource for " + getDescription());
	}

	/**
	 * This implementation always returns <code>null</code>, assuming that this
	 * resource type does not have a filename.
	 */
	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 && ((IResource) obj).getDescription().equals(getDescription())));
	}

	/**
	 * This implementation returns the description's hash code.
	 * 
	 * @see #getDescription()
	 */
	@Override
	public int hashCode() {
		return getDescription().hashCode();
	}

}