Class ElementRemover

java.lang.Object
org.cyberneko.html.filters.DefaultFilter
org.cyberneko.html.filters.ElementRemover
All Implemented Interfaces:
org.apache.xerces.xni.parser.XMLComponent, org.apache.xerces.xni.parser.XMLDocumentFilter, org.apache.xerces.xni.parser.XMLDocumentSource, org.apache.xerces.xni.XMLDocumentHandler, HTMLComponent

public class ElementRemover extends DefaultFilter
This class is a document filter capable of removing specified elements from the processing stream. There are two options for processing document elements:
  • specifying those elements which should be accepted and, optionally, which attributes of that element should be kept; and
  • specifying those elements whose tags and content should be completely removed from the event stream.

The first option allows the application to specify which elements appearing in the event stream should be accepted and, therefore, passed on to the next stage in the pipeline. All elements not in the list of acceptable elements have their start and end tags stripped from the event stream unless those elements appear in the list of elements to be removed.

The second option allows the application to specify which elements should be completely removed from the event stream. When an element appears that is to be removed, the element's start and end tag as well as all of that element's content is removed from the event stream.

A common use of this filter would be to only allow rich-text and linking elements as well as the character content to pass through the filter — all other elements would be stripped. The following code shows how to configure this filter to perform this task:

  ElementRemover remover = new ElementRemover();
  remover.acceptElement("b", null);
  remover.acceptElement("i", null);
  remover.acceptElement("u", null);
  remover.acceptElement("a", new String[] { "href" });
 

However, this would still allow the text content of other elements to pass through, which may not be desirable. In order to further "clean" the input, the removeElement option can be used. The following piece of code adds the ability to completely remove any <SCRIPT> tags and content from the stream.

  remover.removeElement("script");
 

Note: All text and accepted element children of a stripped element is retained. To completely remove an element's content, use the removeElement method.

Note: Care should be taken when using this filter because the output may not be a well-balanced tree. Specifically, if the application removes the <HTML> element (with or without retaining its children), the resulting document event stream will no longer be well-formed.

Version:
$Id: ElementRemover.java,v 1.5 2005/02/14 03:56:54 andyc Exp $
Author:
Andy Clark
  • Field Details

    • NULL

      protected static final Object NULL
      A "null" object.
    • fAcceptedElements

      protected Hashtable fAcceptedElements
      Accepted elements.
    • fRemovedElements

      protected Hashtable fRemovedElements
      Removed elements.
    • fElementDepth

      protected int fElementDepth
      The element depth.
    • fRemovalElementDepth

      protected int fRemovalElementDepth
      The element depth at element removal.
  • Constructor Details

    • ElementRemover

      public ElementRemover()
  • Method Details

    • acceptElement

      public void acceptElement(String element, String[] attributes)
      Specifies that the given element should be accepted and, optionally, which attributes of that element should be kept.
      Parameters:
      element - The element to accept.
      attributes - The list of attributes to be kept or null if no attributes should be kept for this element. see #removeElement
    • removeElement

      public void removeElement(String element)
      Specifies that the given element should be completely removed. If an element is encountered during processing that is on the remove list, the element's start and end tags as well as all of content contained within the element will be removed from the processing stream.
      Parameters:
      element - The element to completely remove.
    • startDocument

      public void startDocument(org.apache.xerces.xni.XMLLocator locator, String encoding, org.apache.xerces.xni.NamespaceContext nscontext, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Start document.
      Specified by:
      startDocument in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      startDocument in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • startDocument

      public void startDocument(org.apache.xerces.xni.XMLLocator locator, String encoding, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Start document.
      Overrides:
      startDocument in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • startPrefixMapping

      public void startPrefixMapping(String prefix, String uri, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Start prefix mapping.
      Overrides:
      startPrefixMapping in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • startElement

      public void startElement(org.apache.xerces.xni.QName element, org.apache.xerces.xni.XMLAttributes attributes, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Start element.
      Specified by:
      startElement in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      startElement in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • emptyElement

      public void emptyElement(org.apache.xerces.xni.QName element, org.apache.xerces.xni.XMLAttributes attributes, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Empty element.
      Specified by:
      emptyElement in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      emptyElement in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • comment

      public void comment(org.apache.xerces.xni.XMLString text, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Comment.
      Specified by:
      comment in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      comment in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • processingInstruction

      public void processingInstruction(String target, org.apache.xerces.xni.XMLString data, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Processing instruction.
      Specified by:
      processingInstruction in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      processingInstruction in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • characters

      public void characters(org.apache.xerces.xni.XMLString text, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Characters.
      Specified by:
      characters in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      characters in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • ignorableWhitespace

      public void ignorableWhitespace(org.apache.xerces.xni.XMLString text, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Ignorable whitespace.
      Specified by:
      ignorableWhitespace in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      ignorableWhitespace in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • startGeneralEntity

      public void startGeneralEntity(String name, org.apache.xerces.xni.XMLResourceIdentifier id, String encoding, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Start general entity.
      Specified by:
      startGeneralEntity in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      startGeneralEntity in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • textDecl

      public void textDecl(String version, String encoding, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Text declaration.
      Specified by:
      textDecl in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      textDecl in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • endGeneralEntity

      public void endGeneralEntity(String name, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      End general entity.
      Specified by:
      endGeneralEntity in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      endGeneralEntity in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • startCDATA

      public void startCDATA(org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      Start CDATA section.
      Specified by:
      startCDATA in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      startCDATA in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • endCDATA

      public void endCDATA(org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      End CDATA section.
      Specified by:
      endCDATA in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      endCDATA in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • endElement

      public void endElement(org.apache.xerces.xni.QName element, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      End element.
      Specified by:
      endElement in interface org.apache.xerces.xni.XMLDocumentHandler
      Overrides:
      endElement in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • endPrefixMapping

      public void endPrefixMapping(String prefix, org.apache.xerces.xni.Augmentations augs) throws org.apache.xerces.xni.XNIException
      End prefix mapping.
      Overrides:
      endPrefixMapping in class DefaultFilter
      Throws:
      org.apache.xerces.xni.XNIException
    • elementAccepted

      protected boolean elementAccepted(String element)
      Returns true if the specified element is accepted.
    • elementRemoved

      protected boolean elementRemoved(String element)
      Returns true if the specified element should be removed.
    • handleOpenTag

      protected boolean handleOpenTag(org.apache.xerces.xni.QName element, org.apache.xerces.xni.XMLAttributes attributes)
      Handles an open tag.