org.htmlparser

Class PrototypicalNodeFactory

public class PrototypicalNodeFactory extends Object implements Serializable, NodeFactory

A node factory based on the prototype pattern. This factory uses the prototype pattern to generate new nodes. These are cloned as needed to form new Text, Remark and Tag nodes.

Text and remark nodes are generated from prototypes accessed via the textPrototype and remarkPrototype properties respectively. Tag nodes are generated as follows:

Prototype tags, in the form of undifferentiated tags, are held in a hash table. On a request for a tag, the attributes are examined for the name of the tag to be created. If a prototype of that name has been registered (exists in the hash table), it is cloned and the clone is given the characteristics ( Attributes, start and end position) of the requested tag.

In the case that no tag has been registered under that name, a generic tag is created from the prototype acessed via the tagPrototype property.

The hash table of registered tags can be automatically populated with all the known tags from the org.htmlparser.tags package when the factory is constructed, or it can start out empty and be populated explicitly.

Here is an example of how to override all text issued from Text.toPlainTextString(), in this case decoding (converting character references), which illustrates the use of setting the text prototype:

 PrototypicalNodeFactory factory = new PrototypicalNodeFactory ();
 factory.setTextPrototype (
     // create a inner class that is a subclass of TextNode
     new TextNode () {
         public String toPlainTextString()
         {
             String original = super.toPlainTextString ();
             return (org.htmlparser.util.Translate.decode (original));
         }
     });
 Parser parser = new Parser ();
 parser.setNodeFactory (factory);
 

Here is an example of using a custom link tag, in this case just printing the URL, which illustrates registering a tag:


 class PrintingLinkTag extends LinkTag
 {
     public void doSemanticAction ()
         throws
             ParserException
     {
         System.out.println (getLink ());
     }
 }
 PrototypicalNodeFactory factory = new PrototypicalNodeFactory ();
 factory.registerTag (new PrintingLinkTag ());
 Parser parser = new Parser ();
 parser.setNodeFactory (factory);
 

Field Summary
protected MapmBlastocyst
The list of tags to return.
protected RemarkmRemark
The prototypical remark node.
protected TagmTag
The prototypical tag node.
protected TextmText
The prototypical text node.
Constructor Summary
PrototypicalNodeFactory()
Create a new factory with all tags registered.
PrototypicalNodeFactory(boolean empty)
Create a new factory.
PrototypicalNodeFactory(Tag tag)
Create a new factory with the given tag as the only registered tag.
PrototypicalNodeFactory(Tag[] tags)
Create a new factory with the given tags registered.
Method Summary
voidclear()
Clean out the registry.
RemarkcreateRemarkNode(Page page, int start, int end)
Create a new remark node.
TextcreateStringNode(Page page, int start, int end)
Create a new string node.
TagcreateTagNode(Page page, int start, int end, Vector attributes)
Create a new tag node.
Tagget(String id)
Gets a tag from the registry.
RemarkgetRemarkPrototype()
Get the object that is cloned to generate remark nodes.
SetgetTagNames()
Get the list of tag names.
TaggetTagPrototype()
Get the object that is cloned to generate tag nodes.
TextgetTextPrototype()
Get the object that is cloned to generate text nodes.
Tagput(String id, Tag tag)
Adds a tag to the registry.
voidregisterTag(Tag tag)
Register a tag.
PrototypicalNodeFactoryregisterTags()
Register all known tags in the tag package.
Tagremove(String id)
Remove a tag from the registry.
voidsetRemarkPrototype(Remark remark)
Set the object to be used to generate remark nodes.
voidsetTagPrototype(Tag tag)
Set the object to be used to generate tag nodes.
voidsetTextPrototype(Text text)
Set the object to be used to generate text nodes.
voidunregisterTag(Tag tag)
Unregister a tag.

Field Detail

mBlastocyst

protected Map mBlastocyst
The list of tags to return. The list is keyed by tag name.

mRemark

protected Remark mRemark
The prototypical remark node.

mTag

protected Tag mTag
The prototypical tag node.

mText

protected Text mText
The prototypical text node.

Constructor Detail

PrototypicalNodeFactory

public PrototypicalNodeFactory()
Create a new factory with all tags registered. Equivalent to PrototypicalNodeFactory(false).

PrototypicalNodeFactory

public PrototypicalNodeFactory(boolean empty)
Create a new factory.

Parameters: empty If true, creates an empty factory, otherwise create a new factory with all tags registered.

PrototypicalNodeFactory

public PrototypicalNodeFactory(Tag tag)
Create a new factory with the given tag as the only registered tag.

Parameters: tag The single tag to register in the otherwise empty factory.

PrototypicalNodeFactory

public PrototypicalNodeFactory(Tag[] tags)
Create a new factory with the given tags registered.

Parameters: tags The tags to register in the otherwise empty factory.

Method Detail

clear

public void clear()
Clean out the registry.

createRemarkNode

public Remark createRemarkNode(Page page, int start, int end)
Create a new remark node.

Parameters: page The page the node is on. start The beginning position of the remark. end The ending positiong of the remark.

Returns: A remark node comprising the indicated characters from the page.

createStringNode

public Text createStringNode(Page page, int start, int end)
Create a new string node.

Parameters: page The page the node is on. start The beginning position of the string. end The ending position of the string.

Returns: A text node comprising the indicated characters from the page.

createTagNode

public Tag createTagNode(Page page, int start, int end, Vector attributes)
Create a new tag node. Note that the attributes vector contains at least one element, which is the tag name (standalone attribute) at position zero. This can be used to decide which type of node to create, or gate other processing that may be appropriate.

Parameters: page The page the node is on. start The beginning position of the tag. end The ending positiong of the tag. attributes The attributes contained in this tag.

Returns: A tag node comprising the indicated characters from the page.

get

public Tag get(String id)
Gets a tag from the registry.

Parameters: id The name of the tag to return.

Returns: The tag registered under the id name, or null if none.

getRemarkPrototype

public Remark getRemarkPrototype()
Get the object that is cloned to generate remark nodes.

Returns: The prototype for Remark nodes.

See Also: PrototypicalNodeFactory

getTagNames

public Set getTagNames()
Get the list of tag names.

Returns: The names of the tags currently registered.

getTagPrototype

public Tag getTagPrototype()
Get the object that is cloned to generate tag nodes. Clones of this object are returned from PrototypicalNodeFactory when no specific tag is found in the list of registered tags.

Returns: The prototype for Tag nodes.

See Also: PrototypicalNodeFactory

getTextPrototype

public Text getTextPrototype()
Get the object that is cloned to generate text nodes.

Returns: The prototype for Text nodes.

See Also: PrototypicalNodeFactory

put

public Tag put(String id, Tag tag)
Adds a tag to the registry.

Parameters: id The name under which to register the tag. For proper operation, the id should be uppercase so it will be matched by a Map lookup. tag The tag to be returned from a PrototypicalNodeFactory call.

Returns: The tag previously registered with that id if any, or null if none.

registerTag

public void registerTag(Tag tag)
Register a tag. Registers the given tag under every id that the tag has (i.e. all names returned by tag.getIds().

For proper operation, the ids are converted to uppercase so they will be matched by a Map lookup.

Parameters: tag The tag to register.

registerTags

public PrototypicalNodeFactory registerTags()
Register all known tags in the tag package. Registers tags from the tag package by calling registerTag().

Returns: 'this' nodefactory as a convenience.

remove

public Tag remove(String id)
Remove a tag from the registry.

Parameters: id The name of the tag to remove.

Returns: The tag that was registered with that id, or null if none.

setRemarkPrototype

public void setRemarkPrototype(Remark remark)
Set the object to be used to generate remark nodes.

Parameters: remark The prototype for Remark nodes. If null the prototype is set to the default (RemarkNode).

See Also: PrototypicalNodeFactory

setTagPrototype

public void setTagPrototype(Tag tag)
Set the object to be used to generate tag nodes. Clones of this object are returned from PrototypicalNodeFactory when no specific tag is found in the list of registered tags.

Parameters: tag The prototype for Tag nodes. If null the prototype is set to the default (TagNode).

See Also: PrototypicalNodeFactory

setTextPrototype

public void setTextPrototype(Text text)
Set the object to be used to generate text nodes.

Parameters: text The prototype for Text nodes. If null the prototype is set to the default (TextNode).

See Also: PrototypicalNodeFactory

unregisterTag

public void unregisterTag(Tag tag)
Unregister a tag. Unregisters the given tag from every id the tag has.

The ids are converted to uppercase to undo the operation of registerTag.

Parameters: tag The tag to unregister.

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