1 /*

     2  * Copyright 1995-2006 Sun Microsystems, Inc.  All Rights Reserved.

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

     4  *

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

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

     7  * published by the Free Software Foundation.  Sun designates this

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

     9  * by Sun in the LICENSE file that accompanied this code.

    10  *

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

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

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

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

    15  * accompanied this code).

    16  *

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

    18  * 2 along with this work; if not, write to the Free Software Foundation,

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

    20  *

    21  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    22  * CA 95054 USA or visit www.sun.com if you need additional information or

    23  * have any questions.

    24  */

    25 

    26 package java.net;

    27 

    28 import java.io.IOException;

    29 

    30 /**

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

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

    33  * <code>URLConnection</code>.

    34  * <p>

    35  * An application does not generally call the

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

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

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

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

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

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

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

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

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

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

    46  * <p>

    47  * If no content handler could be found, URLConnection will

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

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

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

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

    52  * The class name must be of the form:

    53  * <pre>

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

    55  * e.g.

    56  *     YoyoDyne.experimental.text.plain

    57  * </pre>

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

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

    60  * the JVM will need the RuntimePermission "getClassLoader".

    61  *

    62  * @author  James Gosling

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

    64  * @see     java.net.ContentHandlerFactory

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

    66  * @see     java.net.URLConnection

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

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

    69  * @since   JDK1.0

    70  */

    71 abstract public class ContentHandler {

    72     /**

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

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

    75      * creates an object from it.

    76      *

    77      * @param      urlc   a URL connection.

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

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

    80      */

    81     abstract public Object getContent(URLConnection urlc) throws IOException;

    82 

    83     /**

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

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

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

    87      *

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

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

    90      *

    91      * @param      urlc   a URL connection.

    92      * @param      classes      an array of types requested

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

    94      *                 the first match of the suggested types.

    95      *                 null if none of the requested  are supported.

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

    97      * @since 1.3

    98      */

    99     public Object getContent(URLConnection urlc, Class[] classes) throws IOException {

   100         Object obj = getContent(urlc);

   101 

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

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

   104                 return obj;

   105           }

   106         }

   107         return null;

   108     }

   109 

   110 }