org.htmlparser.lexer
Class Lexer

java.lang.Object
  org.htmlparser.lexer.Lexer

All Implemented Interfaces:

NodeFactory, Serializable

public class Lexer

extends Object

implements Serializable, NodeFactory

This class parses the HTML stream into nodes. There are three major types of nodes (lexemes):

RemarkNode

StringNode

TagNode

Each time nextNode() is called, another node is returned until the stream is exhausted, and null is returned.

See Also:

Serialized Form

Field Summary

protected Cursor	mCursor The current position on the page.
protected static int	mDebugLineTrigger Line number to trigger on.
protected NodeFactory	mFactory The factory for new nodes.
protected Page	mPage The page lexemes are retrieved from.

Constructor Summary

Lexer()
Creates a new instance of a Lexer.

Lexer(Page page)
Creates a new instance of a Lexer.

Lexer(String text)
Creates a new instance of a Lexer.

Lexer(URLConnection connection)
Creates a new instance of a Lexer.

Method Summary

Node	createRemarkNode(Page page, int start, int end) Create a new remark node.
Node	createStringNode(Page page, int start, int end) Create a new string node.
Node	createTagNode(Page page, int start, int end, Vector attributes) Create a new tag node.
String	getCurrentLine() Get the current line.
int	getCurrentLineNumber() Get the current line number.
Cursor	getCursor() Get the current scanning position.
NodeFactory	getNodeFactory() Get the current node factory.
Page	getPage() Get the page this lexer is working on.
int	getPosition()
static void	main(String[] args) Mainline for command line operation
protected Node	makeRemark(Cursor cursor) Create a remark node based on the current cursor and the one provided.
protected Node	makeString(Cursor cursor) Create a string node based on the current cursor and the one provided.
protected Node	makeTag(Cursor cursor, Vector attributes) Create a tag node based on the current cursor and the one provided.
Node	nextNode() Get the next node from the source.
Node	nextNode(boolean quotesmart) Get the next node from the source.
protected Node	parseJsp(Cursor cursor) Parse a java server page node.
protected Node	parseRemark(Cursor cursor, boolean quotesmart) Parse a comment.
protected Node	parseString(Cursor cursor, boolean quotesmart) Parse a string node.
protected Node	parseTag(Cursor cursor) Parse a tag.
void	reset() Reset the lexer to start parsing from the beginning again.
protected void	scanJIS(Cursor cursor) Advance the cursor through a JIS escape sequence.
void	setCursor(Cursor cursor) Set the current scanning position.
void	setNodeFactory(NodeFactory factory) Set the current node factory.
void	setPage(Page page) Set the page this lexer is working on.
void	setPosition(int position)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

mPage

protected Page mPage

The page lexemes are retrieved from.

mCursor

protected Cursor mCursor

The current position on the page.

mFactory

protected NodeFactory mFactory

The factory for new nodes.

mDebugLineTrigger

protected static int mDebugLineTrigger

Line number to trigger on. This is tested on each nextNode() call, as an aid to debugging. Alter this value and set a breakpoint on the line after the test. Remember, these line numbers are zero based, while most editors are one based.

See Also:

nextNode()

Constructor Detail

Lexer

public Lexer()

Creates a new instance of a Lexer.

Lexer

public Lexer(Page page)

Creates a new instance of a Lexer.

Parameters:

page - The page with HTML text.

Lexer

public Lexer(String text)

Creates a new instance of a Lexer.

Parameters:

text - The text to parse.

Lexer

public Lexer(URLConnection connection)
      throws ParserException

Creates a new instance of a Lexer.

Parameters:

connection - The url to parse.

Method Detail

reset

public void reset()

Reset the lexer to start parsing from the beginning again. The underlying components are reset such that the next call to nextNode() will return the first lexeme on the page.

getPage

public Page getPage()

Get the page this lexer is working on.

Returns:

The page that nodes are being read from.

setPage

public void setPage(Page page)

Set the page this lexer is working on.

Returns:

The page that nodes will be read from.

getCursor

public Cursor getCursor()

Get the current scanning position.

Returns:

The lexer's cursor position.

setCursor

public void setCursor(Cursor cursor)

Set the current scanning position.

Parameters:

cursor - The lexer's new cursor position.

getNodeFactory

public NodeFactory getNodeFactory()

Get the current node factory.

Returns:

The lexer's node factory.

setNodeFactory

public void setNodeFactory(NodeFactory factory)

Set the current node factory.

Parameters:

factory - The node factory to be used by the lexer.

getPosition

public int getPosition()

setPosition

public void setPosition(int position)

getCurrentLineNumber

public int getCurrentLineNumber()

Get the current line number.

Returns:

The line number the lexer's working on.

getCurrentLine

public String getCurrentLine()

Get the current line.

Returns:

The string the lexer's working on.

nextNode

public Node nextNode()
              throws ParserException

Get the next node from the source.

Returns:

A RemarkNode, StringNode or TagNode, or null if no more lexemes are present.

Throws:

ParserException - If there is a problem with the underlying page.

nextNode

public Node nextNode(boolean quotesmart)
              throws ParserException

Get the next node from the source.

Parameters:

quotesmart - If true, strings ignore quoted contents.

Returns:

A RemarkNode, StringNode or TagNode, or null if no more lexemes are present.

Throws:

ParserException - If there is a problem with the underlying page.

scanJIS

protected void scanJIS(Cursor cursor)
                throws ParserException

Advance the cursor through a JIS escape sequence.

Parameters:

cursor - A cursor positioned within the escape sequence.

Throws:

ParserException

parseString

protected Node parseString(Cursor cursor,
                           boolean quotesmart)
                    throws ParserException

Parse a string node. Scan characters until "</", "<%", "<!" or < followed by a letter is encountered, or the input stream is exhausted, in which case null is returned.

Parameters:

cursor - The position at which to start scanning.

quotesmart - If true, strings ignore quoted contents.

Throws:

ParserException

makeString

protected Node makeString(Cursor cursor)
                   throws ParserException

Create a string node based on the current cursor and the one provided.

Throws:

ParserException

parseTag

protected Node parseTag(Cursor cursor)
                 throws ParserException

Parse a tag. Parse the name and attributes from a start tag.

From the HTML 4.01 Specification, W3C Recommendation 24 December 1999 http://www.w3.org/TR/html4/intro/sgmltut.html#h-3.2.2

3.2.2 Attributes

Elements may have associated properties, called attributes, which may have values (by default, or set by authors or scripts). Attribute/value pairs appear before the final ">" of an element's start tag. Any number of (legal) attribute value pairs, separated by spaces, may appear in an element's start tag. They may appear in any order.

In this example, the id attribute is set for an H1 element: <H1 id="section1"> This is an identified heading thanks to the id attribute </H1> By default, SGML requires that all attribute values be delimited using either double quotation marks (ASCII decimal 34) or single quotation marks (ASCII decimal 39). Single quote marks can be included within the attribute value when the value is delimited by double quote marks, and vice versa. Authors may also use numeric character references to represent double quotes (&#34;) and single quotes (&#39;). For doublequotes authors can also use the character entity reference &quot;.

In certain cases, authors may specify the value of an attribute without any quotation marks. The attribute value may only contain letters (a-z and A-Z), digits (0-9), hyphens (ASCII decimal 45), periods (ASCII decimal 46), underscores (ASCII decimal 95), and colons (ASCII decimal 58). We recommend using quotation marks even when it is possible to eliminate them.

Attribute names are always case-insensitive.

Attribute values are generally case-insensitive. The definition of each attribute in the reference manual indicates whether its value is case-insensitive.

All the attributes defined by this specification are listed in the attribute index.

This method uses a state machine with the following states:

1. state 0 - outside of any attribute
2. state 1 - within attributre name
3. state 2 - equals hit
4. state 3 - within naked attribute value.
5. state 4 - within single quoted attribute value
6. state 5 - within double quoted attribute value
7. state 6 - whitespaces after attribute name could lead to state 2 (=)or state 0

The starting point for the various components is stored in an array of integers that match the initiation point for the states one-for-one, i.e. bookmarks[0] is where state 0 began, bookmarks[1] is where state 1 began, etc. Attributes are stored in a Vector having one slot for each whitespace or attribute/value pair. The first slot is for attribute name (kind of like a standalone attribute).

Parameters:

cursor - The position at which to start scanning.

Returns:

The parsed tag.

Throws:

ParserException

makeTag

protected Node makeTag(Cursor cursor,
                       Vector attributes)
                throws ParserException

Create a tag node based on the current cursor and the one provided.

Throws:

ParserException

parseRemark

protected Node parseRemark(Cursor cursor,
                           boolean quotesmart)
                    throws ParserException

Parse a comment. Parse a remark markup.

From the HTML 4.01 Specification, W3C Recommendation 24 December 1999 http://www.w3.org/TR/html4/intro/sgmltut.html#h-3.2.4

3.2.4 Comments

HTML comments have the following syntax:

<!-- this is a comment -->

<!-- and so is this one,

which occupies more than one line -->

White space is not permitted between the markup declaration open delimiter("<!") and the comment open delimiter ("--"), but is permitted between the comment close delimiter ("--") and the markup declaration close delimiter (">"). A common error is to include a string of hyphens ("---") within a comment. Authors should avoid putting two or more adjacent hyphens inside comments. Information that appears between comments has no special meaning (e.g., character references are not interpreted as such). Note that comments are markup.

This method uses a state machine with the following states:

1. state 0 - prior to the first open delimiter
2. state 1 - prior to the second open delimiter
3. state 2 - prior to the first closing delimiter
4. state 3 - prior to the second closing delimiter
5. state 4 - prior to the terminating >

All comment text (everything excluding the < and >), is included in the remark text. We allow terminators like --!> even though this isn't part of the spec.

Parameters:

cursor - The position at which to start scanning.

quotesmart - If true, strings ignore quoted contents.

Throws:

ParserException

makeRemark

protected Node makeRemark(Cursor cursor)
                   throws ParserException

Create a remark node based on the current cursor and the one provided.

Throws:

ParserException

parseJsp

protected Node parseJsp(Cursor cursor)
                 throws ParserException

Parse a java server page node. Scan characters until "%>" is encountered, or the input stream is exhausted, in which case null is returned.

Parameters:

cursor - The position at which to start scanning.

Throws:

ParserException

createStringNode

public Node createStringNode(Page page,
                             int start,
                             int end)

Create a new string node.

Specified by:

createStringNode in interface NodeFactory

Parameters:

page - The page the node is on.

start - The beginning position of the string.

end - The ending positiong of the string.

createRemarkNode

public Node createRemarkNode(Page page,
                             int start,
                             int end)

Create a new remark node.

Specified by:

createRemarkNode in interface NodeFactory

Parameters:

page - The page the node is on.

start - The beginning position of the remark.

end - The ending positiong of the remark.

createTagNode

public Node 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.

Specified by:

createTagNode in interface NodeFactory

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.

main

public static void main(String[] args)
                 throws MalformedURLException,
                        IOException,
                        ParserException

Mainline for command line operation

Throws:

MalformedURLException

IOException

ParserException