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/* ClassPersistenceDelegate.java - A PersistenceDelegate for the Class type.

   Copyright (C) 2005 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath 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 for more details.

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

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.java.beans.encoder;

import java.beans.Encoder;

import java.beans.Expression;

import java.beans.PersistenceDelegate;

/** <p>The <code>ClassPersistenceDelegate</code> creates

 * <code>Expression</code> instances which denote class resolutions.</p>

 *

 * <p>The class resolution is always the last step when serializing a tree

 * of objects. Due to the recursive nature of the algorithm we need a way

 * to end the recursion. This is achieved by the implementation of this

 * {@link instantiate} method. Arbitrary classes are described with a call

 * to <code>Class.forName</code>. However for the <code>Class</code> class

 * we call <code>getClass()</code> on a <code>String.class</code> instance.

 * This in turn lead to the resolution of the String class which is always

 * encoded as <code>"".getClass()</code>. Finally the <code>Encoder</code>

 * treats strings in a special way so that the recursion ends here.

 *

 * @author Robert Schuster (robertschuster@fsfe.org)

 */

public class ClassPersistenceDelegate extends PersistenceDelegate

{

  protected Expression instantiate(Object oldInstance, Encoder out)

  {

    Class oldClass = (Class) oldInstance;

    // Due to the special handling of String instances in the Encoder

    // this Expression does not lead to further class resolutions.

    if (oldClass == String.class)

      return new Expression(oldClass, "", "getClass", null);

    // This Expression will lead to the class resolution of String.class.

    if (oldClass == Class.class)

      return new Expression(oldClass, String.class, "getClass", null);

    // This Expression will lead to the class resolution of Class.class.

    return new Expression(oldClass, Class.class, "forName",

                          new Object[] { oldClass.getName() });

  }

}