autohit.server.command.CommandRegistry.java Source code

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Here is the source code for autohit.server.command.CommandRegistry.java

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/**
 * AUTOHIT 2003
 * Copyright Erich P Gatejen (c) 1989,1997,2003,2004
 * 
 * This program 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 of the License, or (at
 * your option) any later version.
 * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Additional license information can be found in the documentation.
 * @author Erich P Gatejen
 */
package autohit.server.command;

import java.io.InputStream;

import org.apache.commons.collections.ExtendedProperties;

import autohit.common.Constants;
import autohit.server.ServerException;

/**
 * Command registry implementation.  This is immutable.  Once created it is
 * set.  If you need to catch changes in the registry, you need to create
 * a new instance.  Using the default constructor will cause an exception!
 * <p>
 * This version of the registry will implement it as a ExtendedProperties
 * set.
 * <p>
 * The registry has two sections.  The first section associates the commands
 * with numerics.  There may ne NO duplicate numerics.  (If there are, the system 
 * state is undefined.)  This section is constructed as follows:<p>
 * <code>
 * command.1=compile
 * command.2=dump
 * <br>
 * ("command.")(numeric)("=")(string name)</code><p>
 * The second section contains entries for the commands defined in section one.
 * This section is as follows:<p>
 * <code>
 * compile.class=autohit.server.command.CommandCompile
 * compile.help=This will compile a script found at the target.
 * <br>
 * (string name)(".class=")(class name for implementation)
 * (string name)(".help=")(string giving a hint about the command)</code><p>
 * 
 * @author Erich P. Gatejen
 * @version 1.0
 * <i>Version History</i>
 * <code>EPG - Initial - 25Jul03</code>
 * 
 */
public class CommandRegistry extends ExtendedProperties {

    final static long serialVersionUID = 1;

    /**
     * field literals
     */
    public final static String FL_COMMAND = "command.";
    public final static String FL_CLASS = ".class";
    public final static String FL_HELP = ".help";

    /**
     * Default Constructor.  Don't use!
     * @throws ServerException
     */
    public CommandRegistry() throws ServerException {
        throw new ServerException("Programmer used default constructor for CommandRegsitry.  this is a bug.",
                ServerException.CODE_SW_DETECTED_FAULT);
    }

    /**
     * Constructor to create and load from an input stream.
     * @param is input stream from where to read the registry
     * @throws ServerException
     */
    public CommandRegistry(InputStream is) throws ServerException {
        super();
        try {
            load(is);
        } catch (Exception e) {
            throw new ServerException("Failed to load the command registry.  message=" + e.getMessage(),
                    ServerException.CODE_COMMAND_REGISTRY_FAULT);
        }
    }

    /**
     * Get an instance of the command specified by the numeric
     * @param numeric numeric for the command
     * @throws ServerException
     * @return the object instance.
     */
    public Object instance(int numeric) throws ServerException {

        String name = Constants.UNKNOWN;
        Command target = null;
        String classname = Constants.UNKNOWN;

        try {
            // See if the atom points to a valid command
            String numericS = FL_COMMAND + Integer.toString(numeric);
            if (this.containsKey(numericS)) {

                // Find the name
                name = this.getString(numericS);
                classname = this.getString(name + FL_CLASS);

                // create the instance
                Class t = Class.forName(classname);
                target = (Command) t.newInstance();

            } else {
                throw new ServerException(
                        "Command Registry does not have requested command.  Command ignored.  Command numeric="
                                + numeric,
                        ServerException.CODE_COMMAND_UNKNOWN);
            }

        } catch (ClassCastException cee) {
            throw new ServerException("Command Registry instance() failed because of malformed '.class' entry for "
                    + name + ".  numeric=" + numeric, ServerException.CODE_COMMAND_REGISTRY_FAULT, cee);
        } catch (ClassNotFoundException cne) {
            throw new ServerException(
                    "Command Registry instance() failed because of malformed '.class' entry for " + name
                            + ".  ClassNotFound for entry=[" + classname + "].",
                    ServerException.CODE_COMMAND_REGISTRY_FAULT, cne);
        } catch (ServerException se) {
            throw se;
        } catch (Exception ee) {
            throw new ServerException(
                    "Command Registry instance() failed to gross exception.  message=" + ee.getMessage(),
                    ServerException.CODE_COMMAND_REGISTRY_FAULT, ee);
        }
        return target;
    }
}