/*

 * Copyright 1997-1999 Sun Microsystems, Inc.  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.  Sun designates this

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

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

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

 * have any questions.

 */

package javax.activation;

import java.io.*;

import java.beans.Beans;

/**

 * The CommandInfo class is used by CommandMap implementations to

 * describe the results of command requests. It provides the requestor

 * with both the verb requested, as well as an instance of the

 * bean. There is also a method that will return the name of the

 * class that implements the command but <i>it is not guaranteed to

 * return a valid value</i>. The reason for this is to allow CommandMap

 * implmentations that subclass CommandInfo to provide special

 * behavior. For example a CommandMap could dynamically generate

 * JavaBeans. In this case, it might not be possible to create an

 * object with all the correct state information solely from the class

 * name.

 *

 * @since 1.6

 */

public class CommandInfo {

    private String verb;

    private String className;

    /**

     * The Constructor for CommandInfo.

     * @param verb The command verb this CommandInfo decribes.

     * @param className The command's fully qualified class name.

     */

    public CommandInfo(String verb, String className) {

        this.verb = verb;

        this.className = className;

    }

    /**

     * Return the command verb.

     *

     * @return the command verb.

     */

    public String getCommandName() {

        return verb;

    }

    /**

     * Return the command's class name. <i>This method MAY return null in

     * cases where a CommandMap subclassed CommandInfo for its

     * own purposes.</i> In other words, it might not be possible to

     * create the correct state in the command by merely knowing

     * its class name. <b>DO NOT DEPEND ON THIS METHOD RETURNING

     * A VALID VALUE!</b>

     *

     * @return The class name of the command, or <i>null</i>

     */

    public String getCommandClass() {

        return className;

    }

    /**

     * Return the instantiated JavaBean component.

     * <p>

     * Begin by instantiating the component with

     * <code>Beans.instantiate()</code>.

     * <p>

     * If the bean implements the <code>javax.activation.CommandObject</code>

     * interface, call its <code>setCommandContext</code> method.

     * <p>

     * If the DataHandler parameter is null, then the bean is

     * instantiated with no data. NOTE: this may be useful

     * if for some reason the DataHandler that is passed in

     * throws IOExceptions when this method attempts to

     * access its InputStream. It will allow the caller to

     * retrieve a reference to the bean if it can be

     * instantiated.

     * <p>

     * If the bean does NOT implement the CommandObject interface,

     * this method will check if it implements the

     * java.io.Externalizable interface. If it does, the bean's

     * readExternal method will be called if an InputStream

     * can be acquired from the DataHandler.<p>

     *

     * @param dh        The DataHandler that describes the data to be

     *                  passed to the command.

     * @param loader    The ClassLoader to be used to instantiate the bean.

     * @return The bean

     * @see java.beans.Beans#instantiate

     * @see javax.activation.CommandObject

     */

    public Object getCommandObject(DataHandler dh, ClassLoader loader)

                        throws IOException, ClassNotFoundException {

        Object new_bean = null;

        // try to instantiate the bean

        new_bean = java.beans.Beans.instantiate(loader, className);

        // if we got one and it is a CommandObject

        if (new_bean != null) {

            if (new_bean instanceof CommandObject) {

                ((CommandObject)new_bean).setCommandContext(verb, dh);

            } else if (new_bean instanceof Externalizable) {

                if (dh != null) {

                    InputStream is = dh.getInputStream();

                    if (is != null) {

                        ((Externalizable)new_bean).readExternal(

                                               new ObjectInputStream(is));

                    }

                }

            }

        }

        return new_bean;

    }

}