Parser (Java SE 17 & JDK 17)
Description: declaration: module: java.desktop, package: javax.swing.text.html.parser, class: Parser
Keywords: javax.swing.text.html.parser.Parser class

Module java.desktop
Package javax.swing.text.html.parser

# Class Parser

java.lang.Object
javax.swing.text.html.parser.Parser

All Implemented Interfaces:
  `DTDConstants`

Direct Known Subclasses:
  `DocumentParser`

public class Parser extends Object implements DTDConstants
A simple DTD-driven HTML parser. The parser reads an HTML file from an InputStream and calls various methods (which should be overridden in a subclass) when tags and data are encountered.

Unfortunately there are many badly implemented HTML parsers out there, and as a result there are many badly formatted HTML files. This parser attempts to parse most HTML files. This means that the implementation sometimes deviates from the SGML specification in favor of HTML.

The parser treats \r and \r\n as \n. Newlines after starttags and before end tags are ignored just as specified in the SGML/HTML specification.

The html spec does not specify how spaces are to be coalesced very well. Specifically, the following scenarios are not discussed (note that a space should be used here, but I am using &nbsp to force the space to be displayed):

'<b>blah <i> <strike> foo' which can be treated as: '<b>blah <i><strike>foo'

as well as: '<p><a href="xx"> <em>Using</em></a></p>' which appears to be treated as: '<p><a href="xx"><em>Using</em></a></p>'

If `strict` is false, when a tag that breaks flow, (`TagElement.breaksFlows`) or trailing whitespace is encountered, all whitespace will be ignored until a non whitespace character is encountered. This appears to give behavior closer to the popular browsers.

See Also:
  - `DTD`
  - `TagElement`
  - `SimpleAttributeSet`

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected DTD`
  `dtd`
  The dtd.
  `protected boolean`
  `strict`
  This flag determines whether or not the Parser will be strict in enforcing SGML compatibility.

  ### Fields declared in interface javax.swing.text.html.parser.DTDConstants

  `ANY, CDATA, CONREF, CURRENT, DEFAULT, EMPTY, ENDTAG, ENTITIES, ENTITY, FIXED, GENERAL, ID, IDREF, IDREFS, IMPLIED, MD, MODEL, MS, NAME, NAMES, NMTOKEN, NMTOKENS, NOTATION, NUMBER, NUMBERS, NUTOKEN, NUTOKENS, PARAMETER, PI, PUBLIC, RCDATA, REQUIRED, SDATA, STARTTAG, SYSTEM`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `Parser(DTD dtd)`
  Creates parser with the specified `dtd`.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected void`
  `endTag(boolean omitted)`
  Handle an end tag.
  `protected void`
  `error(String err)`
  Invokes the error handler with the 1st, 2nd and 3rd error message argument "?".
  `protected void`
  `error(String err, String arg1)`
  Invokes the error handler with the 2nd and 3rd error message argument "?".
  `protected void`
  `error(String err, String arg1, String arg2)`
  Invokes the error handler with the 3rd error message argument "?".
  `protected void`
  `error(String err, String arg1, String arg2, String arg3)`
  Invokes the error handler.
  `protected void`
  `flushAttributes()`
  Removes the current attributes.
  `protected SimpleAttributeSet`
  `getAttributes()`
  Returns attributes for the current tag.
  `protected int`
  `getCurrentLine()`
  `protected int`
  `getCurrentPos()`
  Returns the current position.
  `protected void`
  `handleComment(char[] text)`
  Called when an HTML comment is encountered.
  `protected void`
  `handleEmptyTag(TagElement tag)`
  Called when an empty tag is encountered.
  `protected void`
  `handleEndTag(TagElement tag)`
  Called when an end tag is encountered.
  `protected void`
  `handleEOFInComment()`
  Called when the content terminates without closing the HTML comment.
  `protected void`
  `handleError(int ln, String msg)`
  An error has occurred.
  `protected void`
  `handleStartTag(TagElement tag)`
  Called when a start tag is encountered.
  `protected void`
  `handleText(char[] text)`
  Called when PCDATA is encountered.
  `protected void`
  `handleTitle(char[] text)`
  Called when an HTML title tag is encountered.
  `protected TagElement`
  `makeTag(Element elem)`
  Makes a TagElement.
  `protected TagElement`
  `makeTag(Element elem, boolean fictional)`
  Makes a TagElement.
  `protected void`
  `markFirstTime(Element elem)`
  Marks the first time a tag has been seen in a document
  `void`
  `parse(Reader in)`
  Parse an HTML stream, given a DTD.
  `String`
  `parseDTDMarkup()`
  Parses the Document Type Declaration markup declaration.
  `protected boolean`
  `parseMarkupDeclarations(StringBuffer strBuff)`
  Parse markup declarations.
  `protected void`
  `startTag(TagElement tag)`
  Handle a start tag.

  ### Methods declared in class java.lang.Object

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

- ## Field Details

  - ### dtd

    protected DTD dtd
    The dtd.

  - ### strict

    protected boolean strict
    This flag determines whether or not the Parser will be strict in enforcing SGML compatibility. If false, it will be lenient with certain common classes of erroneous HTML constructs. Strict or not, in either case an error will be recorded.

- ## Constructor Details

  - ### Parser

    public Parser(DTD dtd)
    Creates parser with the specified `dtd`.
    Parameters:
      `dtd` - the dtd.

- ## Method Details

  - ### getCurrentLine

    protected int getCurrentLine()
    Returns:
      the line number of the line currently being parsed

  - ### makeTag

    protected TagElement makeTag(Element elem, boolean fictional)
    Makes a TagElement.
    Parameters:
      `elem` - the element storing the tag definition
      `fictional` - the value of the flag "`fictional`" to be set for the tag
    Returns:
      the created `TagElement`

  - ### makeTag

    protected TagElement makeTag(Element elem)
    Makes a TagElement.
    Parameters:
      `elem` - the element storing the tag definition
    Returns:
      the created `TagElement`

  - ### getAttributes

    protected SimpleAttributeSet getAttributes()
    Returns attributes for the current tag.
    Returns:
      `SimpleAttributeSet` containing the attributes

  - ### flushAttributes

    protected void flushAttributes()
    Removes the current attributes.

  - ### handleText

    protected void handleText(char[] text)
    Called when PCDATA is encountered.
    Parameters:
      `text` - the section text

  - ### handleTitle

    protected void handleTitle(char[] text)
    Called when an HTML title tag is encountered.
    Parameters:
      `text` - the title text

  - ### handleComment

    protected void handleComment(char[] text)
    Called when an HTML comment is encountered.
    Parameters:
      `text` - the comment being handled

  - ### handleEOFInComment

    protected void handleEOFInComment()
    Called when the content terminates without closing the HTML comment.

  - ### handleEmptyTag

    protected void handleEmptyTag(TagElement tag) throws ChangedCharSetException
    Called when an empty tag is encountered.
    Parameters:
      `tag` - the tag being handled
    Throws:
      `ChangedCharSetException` - if the document charset was changed

  - ### handleStartTag

    protected void handleStartTag(TagElement tag)
    Called when a start tag is encountered.
    Parameters:
      `tag` - the tag being handled

  - ### handleEndTag

    protected void handleEndTag(TagElement tag)
    Called when an end tag is encountered.
    Parameters:
      `tag` - the tag being handled

  - ### handleError

    protected void handleError(int ln, String msg)
    An error has occurred.
    Parameters:
      `ln` - the number of line containing the error
      `msg` - the error message

  - ### error

    protected void error(String err, String arg1, String arg2, String arg3)
    Invokes the error handler.
    Parameters:
      `err` - the error type
      `arg1` - the 1st error message argument
      `arg2` - the 2nd error message argument
      `arg3` - the 3rd error message argument

  - ### error

    protected void error(String err, String arg1, String arg2)
    Invokes the error handler with the 3rd error message argument "?".
    Parameters:
      `err` - the error type
      `arg1` - the 1st error message argument
      `arg2` - the 2nd error message argument

  - ### error

    protected void error(String err, String arg1)
    Invokes the error handler with the 2nd and 3rd error message argument "?".
    Parameters:
      `err` - the error type
      `arg1` - the 1st error message argument

  - ### error

    protected void error(String err)
    Invokes the error handler with the 1st, 2nd and 3rd error message argument "?".
    Parameters:
      `err` - the error type

  - ### startTag

    protected void startTag(TagElement tag) throws ChangedCharSetException
    Handle a start tag. The new tag is pushed onto the tag stack. The attribute list is checked for required attributes.
    Parameters:
      `tag` - the tag
    Throws:
      `ChangedCharSetException` - if the document charset was changed

  - ### endTag

    protected void endTag(boolean omitted)
    Handle an end tag. The end tag is popped from the tag stack.
    Parameters:
      `omitted` - `true` if the tag is no actually present in the document, but is supposed by the parser

  - ### markFirstTime

    protected void markFirstTime(Element elem)
    Marks the first time a tag has been seen in a document
    Parameters:
      `elem` - the element represented by the tag

  - ### parseDTDMarkup

    public String parseDTDMarkup() throws IOException
    Parses the Document Type Declaration markup declaration. Currently ignores it.
    Returns:
      the string representation of the markup declaration
    Throws:
      `IOException` - if an I/O error occurs

  - ### parseMarkupDeclarations

    protected boolean parseMarkupDeclarations(StringBuffer strBuff) throws IOException
    Parse markup declarations. Currently only handles the Document Type Declaration markup. Returns true if it is a markup declaration false otherwise.
    Parameters:
      `strBuff` - the markup declaration
    Returns:
      `true` if this is a valid markup declaration; otherwise `false`
    Throws:
      `IOException` - if an I/O error occurs

  - ### parse

    public void parse(Reader in) throws IOException
    Parse an HTML stream, given a DTD.
    Parameters:
      `in` - the reader to read the source from
    Throws:
      `IOException` - if an I/O error occurs

  - ### getCurrentPos

    protected int getCurrentPos()
    Returns the current position.
    Returns:
      the current position