WicketRemoveTagHandler.java :  » J2EE » wicket-1.4 » org » apache » wicket » markup » parser » filter » 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.markup.parser.filter;

import java.text.ParseException;

import org.apache.wicket.markup.ComponentTag;
import org.apache.wicket.markup.MarkupElement;
import org.apache.wicket.markup.WicketTag;
import org.apache.wicket.markup.parser.AbstractMarkupFilter;


/**
 * This is a markup inline filter. It identifies preview regions useful for HTML designers to design
 * the page. But they must be removed prior to sending the markup to the client. Preview regions are
 * enclosed by <wicket:remove> tags.
 * 
 * @author Juergen Donnerstag
 */
public final class WicketRemoveTagHandler extends AbstractMarkupFilter
{
  static
  {
    // register "wicket:remove"
    WicketTagIdentifier.registerWellKnownTagName("remove");
  }

  /**
   * Construct.
   */
  public WicketRemoveTagHandler()
  {
  }

  /**
   * Removes preview regions enclosed by <wicket:remove> tags. Note that for obvious
   * reasons, nested components are not allowed.
   * 
   * @see org.apache.wicket.markup.parser.IMarkupFilter#nextTag()
   * @return The next tag to be processed. Null, if not more tags are available
   */
  public final MarkupElement nextTag() throws ParseException
  {
    // Get the next tag from the next MarkupFilter in the chain
    // If null, no more tags are available
    final ComponentTag openTag = (ComponentTag)getParent().nextTag();
    if (openTag == null)
    {
      return openTag;
    }

    // If it is not a remove tag, than we are finished
    if (!(openTag instanceof WicketTag) || !((WicketTag)openTag).isRemoveTag())
    {
      return openTag;
    }

    // remove tag must not be open-close tags
    if (openTag.isOpenClose())
    {
      throw new ParseException("Wicket remove tag must not be an open-close tag: " +
        openTag.toUserDebugString(), openTag.getPos());
    }

    // Find the corresponding close tag and remove all tags in between
    ComponentTag closeTag;
    while (null != (closeTag = (ComponentTag)getParent().nextTag()))
    {
      // No Wicket component tags are allowed within the preview region.
      // Wicket components will a component name assigned.
      if (closeTag.getId() == null)
      {
        continue;
      }

      // The first Wicket component following the preview region open
      // tag, must be it's corresponding close tag.
      if (closeTag.closes(openTag))
      {
        // The tag (from open to close) should be ignored by
        // MarkupParser and not be added to the Markup.
        openTag.setIgnore(true);
        return openTag;
      }

      throw new ParseException(
        "Markup remove regions must not contain Wicket component tags. tag: " +
          closeTag.toUserDebugString(), closeTag.getPos());
    }

    throw new ParseException("Did not find close tag for markup remove region. Open tag: " +
      openTag.toUserDebugString(), openTag.getPos());
  }
}