Resource.java

//
//  ========================================================================
//  Copyright (c) 1995-2015 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.util.resource;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;

import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;

/* ------------------------------------------------------------ */
/**g
 * Abstract resource class.
 */
public abstract class Resource
{
    private static final Logger LOG = Log.getLogger(Resource.class);
    public static boolean __defaultUseCaches = true;
    volatile Object _associate;

    /* ------------------------------------------------------------ */
    /** Construct a resource from a url.
     * @param url A URL.
     * @return A Resource object.
     * @throws IOException Problem accessing URL
     */
    public static Resource newResource(URL url)
        throws IOException
    {
        return newResource(url, __defaultUseCaches);
    }

    /* ------------------------------------------------------------ */
    /**
     * Construct a resource from a url.
     * @param url the url for which to make the resource
     * @param useCaches true enables URLConnection caching if applicable to the type of resource
     * @return
     */
    static Resource newResource(URL url, boolean useCaches)
    {
        if (url==null)
            return null;

        return new URLResource(url,null,useCaches);
    }

    /* ------------------------------------------------------------ */
    /** Construct a resource from a string.
     * @param resource A URL or filename.
     * @return A Resource object.
     */
    public static Resource newResource(String resource)
        throws MalformedURLException, IOException
    {
        return newResource(resource, __defaultUseCaches);
    }

    /* ------------------------------------------------------------ */
    /** Construct a resource from a string.
     * @param resource A URL or filename.
     * @param useCaches controls URLConnection caching
     * @return A Resource object.
     */
    public static Resource newResource (String resource, boolean useCaches)
    throws MalformedURLException, IOException
    {
        URL url=null;
        try
        {
            // Try to format as a URL?
            url = new URL(resource);
        }
        catch(MalformedURLException e)
        {
            LOG.warn("Bad Resource: "+resource);
            throw e;
        }

        return newResource(url);
    }

    /* ------------------------------------------------------------ */
    @Override
    protected void finalize()
    {
        release();
    }

    /* ------------------------------------------------------------ */
    /** Release any temporary resources held by the resource.
     */
    public abstract void release();

    /* ------------------------------------------------------------ */
    /**
     * Returns an input stream to the resource
     */
    public abstract InputStream getInputStream()
        throws java.io.IOException;
}