Class NodeVisitor

The base class for the 'Visitor' pattern. Classes that wish to use visitAllNodesWith() will subclass this class and provide implementations for methods they are interested in processing.

The operation of visitAllNodesWith() is to call beginParsing(), then visitXXX() according to the types of nodes encountered in depth-first order and finally finishedParsing().

Typical code to print all the link tags:

 import org.htmlparser.Parser;
 import org.htmlparser.Tag;
 import org.htmlparser.Text;
 import org.htmlparser.util.ParserException;
 import org.htmlparser.visitors.NodeVisitor;
 
 public class MyVisitor extends NodeVisitor
 {
     public MyVisitor ()
     {
     }

     public void visitTag (Tag tag)
     {
         System.out.println ("\n" + tag.getTagName () + tag.getStartPosition ());
     }

     public void visitStringNode (Text string)
     {
         System.out.println (string);
     }

     public static void main (String[] args) throws ParserException
     {
         Parser parser = new Parser ("http://cbc.ca");
         Visitor visitor = new MyVisitor ();
         parser.visitAllNodesWith (visitor);
     }
 }
 

If you want to handle more than one tag type with the same visitor you will need to check the tag type in the visitTag method. You can do that by either checking the tag name:

     public void visitTag (Tag tag)
     {
        if (tag.getName ().equals ("BODY"))
            ... do something with the BODY tag
        else if (tag.getName ().equals ("FRAME"))
            ... do something with the FRAME tag
    }
 

or you can use instanceof if all the tags you want to handle have a registered tag (i.e. they are generated by the NodeFactory):

     public void visitTag (Tag tag)
     {
        if (tag instanceof BodyTag)
        {
            BodyTag body = (BodyTag)tag;
            ... do something with body
        }
        else if (tag instanceof FrameTag)
        {
            FrameTag frame = (FrameTag)tag;
            ... do something with frame
        }
        else // other specific tags and generic TagNode objects
        {
        }
    }