DefaultObjectFactory

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 *    (http://www.exolab.org/).
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 * THIS SOFTWARE IS PROVIDED BY INTALIO, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
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 * INTALIO, INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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 * Copyright 2003 (C) Intalio, Inc. All Rights Reserved.
 *
 * $Id$
 *
 * Date         Author          Changes
 * 04/21/2003   Keith Visco     Created
 */

package org.exolab.castor.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

import org.exolab.castor.core.exceptions.CastorIllegalStateException;

/**
 * The default implementation of ObjectFactory used for
 * creating class instances
 *
 * @author <a href="mailto:kvisco@intalio.com">Keith Visco</a>
 * @version $Revision$ $Date: 2006-04-25 15:08:23 -0600 (Tue, 25 Apr 2006) $
 * @see ObjectFactory
 */
public class DefaultObjectFactory implements ObjectFactory {

    /**
     * Creates a default instance of the given class.
     *
     * @param type the Class to create an instance of
     * @return the new instance of the given class
     */
    public Object createInstance(Class type)
        throws IllegalAccessException, InstantiationException
    {
        return createInstance(type, null, null);
    } //-- createInstance

    /**
     * Creates a default instance of the given class.
     *
     * @param type the Class to create an instance of
     * @param args the array of arguments to pass to the Class constructor
     * @return the new instance of the given class
     */
    public Object createInstance(Class type, Object[] args)
        throws IllegalAccessException, InstantiationException
    {
        return createInstance(type, null, args);
    } //-- createInstance

    /**
     * Creates a default instance of the given class.
     *
     * @param type the Class to create an instance of
     * @param argTypes the Class types for each argument, used
     * to find the correct constructor
     * @param args the array of arguments to pass to the Class constructor
     * @return the new instance of the given class
     */
    public Object createInstance(Class type, Class[] argTypes, Object[] args)
        throws IllegalAccessException, InstantiationException
    {
        if ((args == null) || (args.length == 0)) {
            if (java.util.Date.class.isAssignableFrom(type)) {
                return handleDates(type);
            }
            return type.newInstance();
        }

        argTypes = checkArguments(argTypes, args);

        return instantiateUsingConstructor(type, argTypes, args);

    } //-- createInstance

    /**
     * Create a new instance of the given type by calling a public constructor
     * of this class, passing the given arguments to the constructor call.
     * @param type The class type to instantiate
     * @param argTypes Argument types.
     * @param args Arguments (to be used as parameters to the constructor class).
     * @return An instance of the class type provided
     * @throws InstantiationException If the given class type does not expose a constructor
     *  with the given number of argument (types).
     * @throws IllegalAccessException If the given constructor failed during invocation.
     */
    private Object instantiateUsingConstructor(Class type, Class[] argTypes, Object[] args) throws InstantiationException, IllegalAccessException {
        try {
            Constructor cons = type.getConstructor(argTypes);
            return cons.newInstance(args);
        }
        catch(java.lang.NoSuchMethodException nsmx) {
            String err = "unable to find matching public constructor for class: " + type.getName();
            err += " with argument types: ";
            for (int i = 0; i < argTypes.length; i++) {
                if (i > 0) err += ", ";
                err += argTypes[i].getName();
            }
            throw new InstantiationException(err);
        } catch(InvocationTargetException ite) {
            throw new CastorIllegalStateException(
                    ite.getMessage(), ite.getTargetException());
        }
    }

    /**
     * Check the arguments (incl. argument types, if provided) for consistency, and
     * deduce argument types if not provided.
     * @param argTypes Argumemnt types.
     * @param args Arguments
     * @return A class array for the argument types provided.
     */
    private Class[] checkArguments(Class[] argTypes, Object[] args) {
        if (argTypes == null) {
            argTypes = new Class[args.length];
            for (int i = 0; i < args.length; i++) {
                if (args[i] != null) {
                    argTypes[i] = args[i].getClass();
                } else {
                    String err = "null arguments to constructor not accepted " +
                        "if the 'argTypes' array is null.";
                    throw new IllegalStateException(getClass().getName() + ": " + err);
                }
            }
        } else if (argTypes.length != args.length) {
            String err = "The argument type array must be the same length as argument value array.";
            throw new IllegalArgumentException(getClass().getName() + ": " + err);
        }
        return argTypes;
    }


    /**
     * Handles 'Date' types in a special way.
     * @param type The Class type
     * @return A new instance of the type given
     * @throws InstantiationException If the given class type cannot be successfully instantiated.
     * @throws IllegalAccessException If the given constructor failed during invocation.
     */
    private Object handleDates(Class type)
        throws IllegalAccessException, InstantiationException
    {

        java.util.Date date = new java.util.Date();

        if (java.util.Date.class == type) {
            return date;
        }
        else if (java.sql.Date.class == type) {
            long time = date.getTime();
            return new java.sql.Date(time);
        }
        else if (java.sql.Time.class == type) {
            long time = date.getTime();
            return new java.sql.Time(time);
        }
        else if (java.sql.Timestamp.class == type) {
            long time = date.getTime();
            return new java.sql.Timestamp(time);
        }
        else {
            return type.newInstance();
        }

    } //-- handleDates

} //-- DefaultObjectFactory