org.htmlparser.nodes

Class AbstractNode

Implemented Interfaces:
Cloneable, Node, Serializable
Known Direct Subclasses:
RemarkNode, TagNode, TextNode

public abstract class AbstractNode
extends Object
implements Node, Serializable

The concrete base class for all types of nodes (tags, text remarks). This class provides basic functionality to hold the Page, the starting and ending position in the page, the parent and the list of children.

Field Summary

protected NodeList
children
The children of this node.
protected Page
mPage
The page this node came from.
protected int
nodeBegin
The beginning position of the tag in the line
protected int
nodeEnd
The ending position of the tag in the line
protected Node
parent
The parent of this node.

Constructor Summary

AbstractNode(Page page, int start, int end)
Create an abstract node with the page positions given.

Method Summary

abstract void
accept(NodeVisitor visitor)
Visit this node.
Object
clone()
Clone this object.
void
collectInto(NodeList list, NodeFilter filter)
Collect this node and its child nodes (if-applicable) into the collectionList parameter, provided the node satisfies the filtering criteria.
void
doSemanticAction()
Perform the meaning of this tag.
NodeList
getChildren()
Get the children of this node.
int
getEndPosition()
Gets the ending position of the node.
Node
getFirstChild()
Get the first child of this node.
Node
getLastChild()
Get the last child of this node.
Node
getNextSibling()
Get the next sibling to this node.
Page
getPage()
Get the page this node came from.
Node
getParent()
Get the parent of this node.
Node
getPreviousSibling()
Get the previous sibling to this node.
int
getStartPosition()
Gets the starting position of the node.
String
getText()
Returns the text of the node.
void
setChildren(NodeList children)
Set the children of this node.
void
setEndPosition(int position)
Sets the ending position of the node.
void
setPage(Page page)
Set the page this node came from.
void
setParent(Node node)
Sets the parent of this node.
void
setStartPosition(int position)
Sets the starting position of the node.
void
setText(String text)
Sets the string contents of the node.
String
toHtml()
Return the HTML for this node.
abstract String
toHtml(boolean verbatim)
Return the HTML for this node.
abstract String
toPlainTextString()
Returns a string representation of the node.
abstract String
toString()
Return a string representation of the node.

Field Details

children

protected NodeList children
The children of this node.

mPage

protected Page mPage
The page this node came from.

nodeBegin

protected int nodeBegin
The beginning position of the tag in the line

nodeEnd

protected int nodeEnd
The ending position of the tag in the line

parent

protected Node parent
The parent of this node.

Constructor Details

AbstractNode

public AbstractNode(Page page,
                    int start,
                    int end)
Create an abstract node with the page positions given. Remember the page and start & end cursor positions.
Parameters:
page - The page this tag was read from.
start - The starting offset of this node within the page.
end - The ending offset of this node within the page.

Method Details

accept

public abstract void accept(NodeVisitor visitor)
Visit this node.
Specified by:
accept in interface Node
Parameters:
visitor - The visitor that is visiting this node.

clone

public Object clone()
            throws CloneNotSupportedException
Clone this object. Exposes java.lang.Object clone as a public method.
Specified by:
clone in interface Node
Returns:
A clone of this object.

collectInto

public void collectInto(NodeList list,
                        NodeFilter filter)
Collect this node and its child nodes (if-applicable) into the collectionList parameter, provided the node satisfies the filtering criteria.

This mechanism allows powerful filtering code to be written very easily, without bothering about collection of embedded tags separately. e.g. when we try to get all the links on a page, it is not possible to get it at the top-level, as many tags (like form tags), can contain links embedded in them. We could get the links out by checking if the current node is a CompositeTag, and going through its children. So this method provides a convenient way to do this.

Using collectInto(), programs get a lot shorter. Now, the code to extract all links from a page would look like:

 NodeList collectionList = new NodeList();
 NodeFilter filter = new TagNameFilter ("A");
 for (NodeIterator e = parser.elements(); e.hasMoreNodes();)
      e.nextNode().collectInto(collectionList, filter);
 
Thus, collectionList will hold all the link nodes, irrespective of how deep the links are embedded.

Another way to accomplish the same objective is:

 NodeList collectionList = new NodeList();
 NodeFilter filter = new TagClassFilter (LinkTag.class);
 for (NodeIterator e = parser.elements(); e.hasMoreNodes();)
      e.nextNode().collectInto(collectionList, filter);
 
This is slightly less specific because the LinkTag class may be registered for more than one node name, e.g. <LINK> tags too.
Specified by:
collectInto in interface Node
Parameters:
list - The node list to collect acceptable nodes into.
filter - The filter to determine which nodes are retained.

doSemanticAction

public void doSemanticAction()
            throws ParserException
Perform the meaning of this tag. The default action is to do nothing.
Specified by:
doSemanticAction in interface Node
Throws:
ParserException - Not used. Provides for subclasses that may want to indicate an exceptional condition.

getChildren

public NodeList getChildren()
Get the children of this node.
Specified by:
getChildren in interface Node
Returns:
The list of children contained by this node, if it's been set, null otherwise.

getEndPosition

public int getEndPosition()
Gets the ending position of the node.
Specified by:
getEndPosition in interface Node
Returns:
The end position.

getFirstChild

public Node getFirstChild()
Get the first child of this node.
Specified by:
getFirstChild in interface Node
Returns:
The first child in the list of children contained by this node, null otherwise.

getLastChild

public Node getLastChild()
Get the last child of this node.
Specified by:
getLastChild in interface Node
Returns:
The last child in the list of children contained by this node, null otherwise.

getNextSibling

public Node getNextSibling()
Get the next sibling to this node.
Specified by:
getNextSibling in interface Node
Returns:
The next sibling to this node if one exists, null otherwise.

getPage

public Page getPage()
Get the page this node came from.
Specified by:
getPage in interface Node
Returns:
The page that supplied this node.

getParent

public Node getParent()
Get the parent of this node. This will always return null when parsing without scanners, i.e. if semantic parsing was not performed. The object returned from this method can be safely cast to a CompositeTag.
Specified by:
getParent in interface Node
Returns:
The parent of this node, if it's been set, null otherwise.

getPreviousSibling

public Node getPreviousSibling()
Get the previous sibling to this node.
Specified by:
getPreviousSibling in interface Node
Returns:
The previous sibling to this node if one exists, null otherwise.

getStartPosition

public int getStartPosition()
Gets the starting position of the node.
Specified by:
getStartPosition in interface Node
Returns:
The start position.

getText

public String getText()
Returns the text of the node.
Specified by:
getText in interface Node
Returns:
The text of this node. The default is null.

setChildren

public void setChildren(NodeList children)
Set the children of this node.
Specified by:
setChildren in interface Node
Parameters:
children - The new list of children this node contains.

setEndPosition

public void setEndPosition(int position)
Sets the ending position of the node.
Specified by:
setEndPosition in interface Node
Parameters:
position - The new end position.

setPage

public void setPage(Page page)
Set the page this node came from.
Specified by:
setPage in interface Node
Parameters:
page - The page that supplied this node.

setParent

public void setParent(Node node)
Sets the parent of this node.
Specified by:
setParent in interface Node
Parameters:
node - The node that contains this node. Must be a CompositeTag.

setStartPosition

public void setStartPosition(int position)
Sets the starting position of the node.
Specified by:
setStartPosition in interface Node
Parameters:
position - The new start position.

setText

public void setText(String text)
Sets the string contents of the node.
Specified by:
setText in interface Node
Parameters:
text - The new text for the node.

toHtml

public String toHtml()
Return the HTML for this node. This should be the sequence of characters that were encountered by the parser that caused this node to be created. Where this breaks down is where broken nodes (tags and remarks) have been encountered and fixed. Applications reproducing html can use this method on nodes which are to be used or transferred as they were received or created.
Specified by:
toHtml in interface Node
Returns:
The sequence of characters that would cause this node to be returned by the parser or lexer.

toHtml

public abstract String toHtml(boolean verbatim)
Return the HTML for this node. This should be the exact sequence of characters that were encountered by the parser that caused this node to be created. Where this breaks down is where broken nodes (tags and remarks) have been encountered and fixed. Applications reproducing html can use this method on nodes which are to be used or transferred as they were received or created.
Specified by:
toHtml in interface Node
Parameters:
verbatim - If true return as close to the original page text as possible.
Returns:
The (exact) sequence of characters that would cause this node to be returned by the parser or lexer.

toPlainTextString

public abstract String toPlainTextString()
Returns a string representation of the node. It allows a simple string transformation of a web page, regardless of node type.
Typical application code (for extracting only the text from a web page) would then be simplified to:
 Node node;
 for (Enumeration e = parser.elements (); e.hasMoreElements (); )
 {
     node = (Node)e.nextElement();
     System.out.println (node.toPlainTextString ());
     // or do whatever processing you wish with the plain text string
 }
 
Specified by:
toPlainTextString in interface Node
Returns:
The 'browser' content of this node.

toString

public abstract String toString()
Return a string representation of the node. Subclasses must define this method, and this is typically to be used in the manner
System.out.println(node)
Specified by:
toString in interface Node
Returns:
A textual representation of the node suitable for debugging

HTML Parser is an open source library released under LGPL. SourceForge.net