/*

 * Copyright (c) 1995, 2011, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

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 */

package java.net;

import java.io.IOException;

/**

 * The abstract class <code>ContentHandler</code> is the superclass

 * of all classes that read an <code>Object</code> from a

 * <code>URLConnection</code>.

 * <p>

 * An application does not generally call the

 * <code>getContent</code> method in this class directly. Instead, an

 * application calls the <code>getContent</code> method in class

 * <code>URL</code> or in <code>URLConnection</code>.

 * The application's content handler factory (an instance of a class that

 * implements the interface <code>ContentHandlerFactory</code> set

 * up by a call to <code>setContentHandler</code>) is

 * called with a <code>String</code> giving the MIME type of the

 * object being received on the socket. The factory returns an

 * instance of a subclass of <code>ContentHandler</code>, and its

 * <code>getContent</code> method is called to create the object.

 * <p>

 * If no content handler could be found, URLConnection will

 * look for a content handler in a user-defineable set of places.

 * By default it looks in sun.net.www.content, but users can define a

 * vertical-bar delimited set of class prefixes to search through in

 * addition by defining the java.content.handler.pkgs property.

 * The class name must be of the form:

 * <pre>

 *     {package-prefix}.{major}.{minor}

 * e.g.

 *     YoyoDyne.experimental.text.plain

 * </pre>

 * If the loading of the content handler class would be performed by

 * a classloader that is outside of the delegation chain of the caller,

 * the JVM will need the RuntimePermission "getClassLoader".

 *

 * @author  James Gosling

 * @see     java.net.ContentHandler#getContent(java.net.URLConnection)

 * @see     java.net.ContentHandlerFactory

 * @see     java.net.URL#getContent()

 * @see     java.net.URLConnection

 * @see     java.net.URLConnection#getContent()

 * @see     java.net.URLConnection#setContentHandlerFactory(java.net.ContentHandlerFactory)

 * @since   JDK1.0

 */

abstract public class ContentHandler {

    /**

     * Given a URL connect stream positioned at the beginning of the

     * representation of an object, this method reads that stream and

     * creates an object from it.

     *

     * @param      urlc   a URL connection.

     * @return     the object read by the <code>ContentHandler</code>.

     * @exception  IOException  if an I/O error occurs while reading the object.

     */

    abstract public Object getContent(URLConnection urlc) throws IOException;

    /**

     * Given a URL connect stream positioned at the beginning of the

     * representation of an object, this method reads that stream and

     * creates an object that matches one of the types specified.

     *

     * The default implementation of this method should call getContent()

     * and screen the return type for a match of the suggested types.

     *

     * @param      urlc   a URL connection.

     * @param      classes      an array of types requested

     * @return     the object read by the <code>ContentHandler</code> that is

     *                 the first match of the suggested types.

     *                 null if none of the requested  are supported.

     * @exception  IOException  if an I/O error occurs while reading the object.

     * @since 1.3

     */

        Object obj = getContent(urlc);

        for (int i = 0; i < classes.length; i++) {

          if (classes[i].isInstance(obj)) {

                return obj;

          }

        }

        return null;

    }

}