DefaultObjectFactory

/**
 * Redistribution and use of this software and associated documentation ("Software"), with or
 * without modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright statements and notices. Redistributions
 * must also contain a copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
 * conditions and the following disclaimer in the documentation and/or other materials provided with
 * the distribution.
 *
 * 3. The name "Exolab" must not be used to endorse or promote products derived from this Software
 * without prior written permission of Intalio, Inc. For written permission, please contact
 * info@exolab.org.
 *
 * 4. Products derived from this Software may not be called "Exolab" nor may "Exolab" appear in
 * their names without prior written permission of Intalio, Inc. Exolab is a registered trademark of
 * Intalio, Inc.
 *
 * 5. Due credit should be given to the Exolab Project (http://www.exolab.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY INTALIO, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESSED OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTALIO, INC. OR ITS
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * 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