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 *
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 * must also contain a copy of this document.
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 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
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 * the distribution.
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 * without prior written permission of Intalio, Inc. For written permission, please contact
 * info@exolab.org.
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 * 4. Products derived from this Software may not be called "Exolab" nor may "Exolab" appear in
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 * Intalio, Inc.
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 * 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
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 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 2002 (C) Intalio, Inc. All Rights Reserved.
 *
 * $Id$
 */
package org.exolab.castor.xml.handlers;

import org.exolab.castor.mapping.FieldHandler;
import org.exolab.castor.mapping.ValidityException;
import org.exolab.castor.xml.util.ContainerElement;

/**
 * The FieldHandler for ContainerElement.
 *
 * @author <a href="kvisco@intalio.com">Keith Visco</a>
 * @version $Revision$ $Date: 2006-04-25 15:08:23 -0600 (Tue, 25 Apr 2006) $
 * @see FieldDescriptor org.exolab.castor.mapping.FieldDescriptor
 * @see FieldHandler org.exolab.castor.mapping.FieldHandler
 */
public final class ContainerFieldHandler implements FieldHandler {

  /** Automatically choose the mode to use. */
  public static final int MODE_AUTO = 0;
  /** When the field is not a ContainerElement, this mode is used. */
  public static final int MODE_PARENT_LINK = 1;
  /** The mode for a ContainerElement. getValue and setValue operate on the parent. */
  public static final int MODE_CHILD_LINK = 2;

  /** The actual FieldHandler to delegate to. */
  private final FieldHandler _handler;
  /** Mode to use for this ContainerFieldHandler. */
  private final int _mode = MODE_AUTO;

  /**
   * Creates a new ContainerFieldHandler with the given FieldHandler.
   * 
   * @param handler The field handler to delegate to.
   */
  public ContainerFieldHandler(final FieldHandler handler) {
    super();
    _handler = handler;
  } // -- ContainerFieldHandler

  // -----------------------------/
  // - Methods from FieldHandler -/
  // -----------------------------/

  /**
   * Returns the value of the field from the object. If mode is MODE_CHILD_LINK or mode is MODE_AUTO
   * and the object is a ContainerElement, then the value of the parent is returned. Otherwise, a
   * new ContainerElement is returned. The value of this new ContainerElement is the value of the
   * provided object and the parent of the new ContainerElement is the provided object.
   *
   * @param object The object to get the value of
   * @return The value of the field
   * @throws IllegalStateException The Java object has changed and is no longer supported by this
   *         handler, or the handler is not compatible with the Java object
   */
  public Object getValue(final Object object) throws IllegalStateException {
    int mode = _mode;
    if (mode == MODE_AUTO) {
      if (object instanceof ContainerElement) {
        mode = MODE_CHILD_LINK;
      } else {
        mode = MODE_PARENT_LINK;
      }
    }

    if (mode == MODE_CHILD_LINK) {
      return _handler.getValue(((ContainerElement) object).getParent());
    }

    // MODE_PARENT_LINK
    ContainerElement container = new ContainerElement(_handler.getValue(object));
    container.setParent(object);
    return container;
  } // -- getValue

  /**
   * Creates a new instance of the object described by this field. Of the object provided is a
   * ContainerElement, then a new isntance of the parent object is returned. Otherwise a new
   * ContainerElement is created and returned, with the parent set to the provided object.
   *
   * @param parent The object for which the field is created
   * @return A new instance of the field's value
   * @throws IllegalStateException This field is a simple type and cannot be instantiated
   */
  public Object newInstance(final Object parent) throws IllegalStateException {
    // -- MODE_CHILD_LINK and MODE_AUTO
    if (parent instanceof ContainerElement) {
      return _handler.newInstance(((ContainerElement) parent).getParent());
    }

    // MODE_PARENT_LINK
    ContainerElement container = new ContainerElement();
    container.setParent(parent);
    return container;
  } // -- newInstance

  /**
   * Sets the value of the field to a default value.
   * <p>
   * Reference fields are set to null, primitive fields are set to their default value, collection
   * fields are emptied of all elements.
   *
   * @param object The object
   * @throws IllegalStateException The Java object has changed and is no longer supported by this
   *         handler, or the handler is not compatiable with the Java object
   */
  public void resetValue(final Object object) throws IllegalStateException {
    _handler.resetValue(object);
  }

  /**
   * Sets the value of the field on the object. That is, sets the value of the container parent to
   * the provided value.
   *
   * @param object The object whose value to set.
   * @param value The new value
   * @throws IllegalStateException The Java object has changed and is no longer supported by this
   *         handler, or the handler is not compatiable with the Java object
   * @throws IllegalArgumentException The value passed is not of a supported type
   */
  public void setValue(final Object object, final Object value)
      throws IllegalStateException, IllegalArgumentException {
    if (_mode == MODE_PARENT_LINK) {
      // Do nothing for MODE_PARENT_LINK; the container is not part of the object model
      return;
    }

    // For MODE_AUTO and MODE_CHILD_LINK:
    if (object instanceof ContainerElement) {
      _handler.setValue(((ContainerElement) object).getParent(), value);
    }
  } // -- setValue

  /**
   * Checks the field validity. Returns successfully if the field can be stored, is valid, etc,
   * throws an exception otherwise.
   *
   * @param object The object
   * @throws ValidityException The field is invalid, is required and null, or any other validity
   *         violation
   * @throws IllegalStateException The Java object has changed and is no longer supported by this
   *         handler, or the handler is not compatiable with the Java object
   */
  public void checkValidity(final Object object) throws ValidityException, IllegalStateException {
    // -- deprecated...do nothing
  } // -- checkValidity

} // -- ContainerFieldHandler
