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/OpenJDK 21

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:

Field Summary

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

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()
Returns the line number of the line currently being parsed.
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.
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

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/21/docs/api/java.desktop/javax/swing/text/html/parser/Parser.html