org.htmlparser.visitors
Class NodeVisitor
public abstract 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
{
}
}
NodeVisitor() - Creates a node visitor that recurses itself and it's children.
|
NodeVisitor(boolean recurseChildren) - Creates a node visitor that recurses itself and it's children
only if
recurseChildren is true .
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NodeVisitor(boolean recurseChildren, boolean recurseSelf) - Creates a node visitor that recurses itself only if
recurseSelf is true and it's children
only if recurseChildren is true .
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NodeVisitor
public NodeVisitor()
Creates a node visitor that recurses itself and it's children.
NodeVisitor
public NodeVisitor(boolean recurseChildren)
Creates a node visitor that recurses itself and it's children
only if recurseChildren
is true
.
recurseChildren
- If true
, the visitor will
visit children, otherwise only the top level nodes are recursed.
NodeVisitor
public NodeVisitor(boolean recurseChildren,
boolean recurseSelf)
Creates a node visitor that recurses itself only if
recurseSelf
is true
and it's children
only if recurseChildren
is true
.
recurseChildren
- If true
, the visitor will
visit children, otherwise only the top level nodes are recursed.recurseSelf
- If true
, the visitor will
visit the top level node.
beginParsing
public void beginParsing()
Override this method if you wish to do special
processing prior to the start of parsing.
finishedParsing
public void finishedParsing()
Override this method if you wish to do special
processing upon completion of parsing.
shouldRecurseChildren
public boolean shouldRecurseChildren()
Depth traversal predicate.
true
if children are to be visited.
shouldRecurseSelf
public boolean shouldRecurseSelf()
Self traversal predicate.
true
if a node itself is to be visited.
visitEndTag
public void visitEndTag(Tag tag)
Called for each Tag
visited that is an end tag.
tag
- The end tag being visited.
visitRemarkNode
public void visitRemarkNode(Remark remark)
Called for each RemarkNode
visited.
remark
- The remark node being visited.
visitStringNode
public void visitStringNode(Text string)
Called for each StringNode
visited.
string
- The string node being visited.
visitTag
public void visitTag(Tag tag)
Called for each Tag
visited.
tag
- The tag being visited.
| © 2005 Derrick Oswald Mai 08, 2008 |
HTML Parser is an open source library released under LGPL. |  |