MarkupFragmentFinder.java :  » J2EE » wicket-1.4 » org » apache » wicket » Java Open Source

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.wicket;

import org.apache.wicket.markup.ComponentTag;
import org.apache.wicket.markup.MarkupElement;
import org.apache.wicket.markup.MarkupStream;
import org.apache.wicket.markup.html.border.Border;
import org.apache.wicket.markup.html.panel.Fragment;

/**
 * Responding to an AJAX request requires that we position the markup stream at the component
 * associated with the AJAX request. That is straight forward in most cases except for "transparent"
 * components and for components which implement there own IComponentResolver.
 * 
 * @author Juergen Donnerstag
 */
final class MarkupFragmentFinder
{
  /**
   * Construct
   */
  public MarkupFragmentFinder()
  {
  }

  /**
   * Get the markup stream and position it at the component
   * 
   * @param component
   * @return A MarkupStream which is positioned at the component
   */
  final MarkupStream find(final Component component)
  {
    // Get the parent's associated markup stream.
    MarkupContainer parentWithAssociatedMarkup = component.findParentWithAssociatedMarkup();
    MarkupStream markupStream = null;

    // Might be that we have to walk up the component hierarchy
    while (true)
    {
      markupStream = parentWithAssociatedMarkup.getAssociatedMarkupStream(true);

      // In case the component has already been rendered, this is a
      // performance short cut. But actually this was necessary because
      // transparent containers and components which implement
      // IComponentResolver destroy the 1:1 match between component path
      // and markup path.
      if (component.markupIndex != -1)
      {
        // Might be that the markup has been reloaded and that the
        // position has changed. Make sure the component is still
        // available
        try
        {
          markupStream.setCurrentIndex(component.markupIndex);
          MarkupElement elem = markupStream.get();
          if (elem instanceof ComponentTag)
          {
            ComponentTag tag = (ComponentTag)elem;
            String id = tag.getId();
            if ((id != null) && id.equals(component.getId()))
            {
              // Ok, found it
              return markupStream;
            }
            else
            {
              // WICKET-1560
              Component parent = component.getParent();
              if (id != null && id.equals(parent.getId()))
              {
                return markupStream;
              }
            }
          }
        }
        catch (IndexOutOfBoundsException ex)
        {
          // fall through. Don't do anything
        }
      }

      // Make sure the markup stream is positioned at the correct element
      String relativePath = getComponentRelativePath(component, parentWithAssociatedMarkup);

      // If the component is defined in the markup
      int index = markupStream.findComponentIndex(relativePath, component.getId());
      if (index != -1)
      {
        // than position the stream at the beginning of the component
        markupStream.setCurrentIndex(index);
        return markupStream;
      }

      if (parentWithAssociatedMarkup instanceof Fragment)
      {
        markupStream = ((Fragment)parentWithAssociatedMarkup).findComponentIndex(component.getId());
        return markupStream;
      }

      // Yet another exception for Border in the code base.
      // However if the container with the markup is a Border, than
      // ...
      if (parentWithAssociatedMarkup instanceof Border)
      {
        parentWithAssociatedMarkup = parentWithAssociatedMarkup.findParentWithAssociatedMarkup();
      }
      else
      {
        throw new WicketRuntimeException(
          "Unable to find the markup for the component. That may be due to transparent containers or components implementing IComponentResolver: " +
            component.toString());
      }

      // Not found, reset the stream
      markupStream = null;
    }
  }

  /**
   * Get component path relative to the parent container with associated markup
   * 
   * @param component
   * @param parentWithAssociatedMarkup
   * @return the relative path
   */
  private String getComponentRelativePath(final Component component,
    final MarkupContainer parentWithAssociatedMarkup)
  {
    final String componentPath = component.getParent().getPageRelativePath();
    final String parentWithAssociatedMarkupPath = parentWithAssociatedMarkup.getPageRelativePath();
    String relativePath = componentPath.substring(parentWithAssociatedMarkupPath.length());
    if (relativePath.startsWith(":"))
    {
      relativePath = relativePath.substring(1);
    }
    return relativePath;
  }
}