org.htmlparser.visitors
public abstract class NodeVisitor extends Object
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 {@link org.htmlparser.PrototypicalNodeFactory#registerTag 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 { } }
Constructor Summary | |
---|---|
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 . | |
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 . |
Method Summary | |
---|---|
void | beginParsing()
Override this method if you wish to do special
processing prior to the start of parsing. |
void | finishedParsing()
Override this method if you wish to do special
processing upon completion of parsing. |
boolean | shouldRecurseChildren()
Depth traversal predicate. |
boolean | shouldRecurseSelf()
Self traversal predicate. |
void | visitEndTag(Tag tag)
Called for each Tag visited that is an end tag. |
void | visitRemarkNode(Remark remark)
Called for each RemarkNode visited. |
void | visitStringNode(Text string)
Called for each StringNode visited. |
void | visitTag(Tag tag)
Called for each Tag visited. |
recurseChildren
is true
.Parameters: recurseChildren If true
, the visitor will
visit children, otherwise only the top level nodes are recursed.
recurseSelf
is true
and it's children
only if recurseChildren
is true
.Parameters: 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.
Returns: true
if children are to be visited.
Returns: true
if a node itself is to be visited.
Tag
visited that is an end tag.Parameters: tag The end tag being visited.
RemarkNode
visited.Parameters: remark The remark node being visited.
StringNode
visited.Parameters: string The string node being visited.
Tag
visited.Parameters: tag The tag being visited.
HTML Parser is an open source library released under LGPL. | |