lava.text.html
Class HtmlParser

java.lang.Object
  |
  +--lava.text.html.HtmlParser

public class HtmlParser

extends java.lang.Object

Parses HTML source.

Details: This class parses HTML source by separating the source components into tags, text, and comments. HtmlParser reads text from a PushbackReader and returns a stream of objects representing parsed entities. Each of the objects is an instance of HtmlComponent, which has many subclasses (refer to the see-also section).

To gain an appreciation for the manner in which HtmlParser is able to parse and tokenize HTML source, the following sample program is provided. Try this program on your favorite URL.

import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import lava.io.UnlimitedPushbackReader;
import lava.io.UrlInputStream;
import lava.string.StringEncoder;
import lava.text.ParallelColumnsWriter;
import lava.text.html.HtmlComponent;
import lava.text.html.HtmlParser;



class parseHtml
{



    public static void main (String[] args) throws Exception
    {
        if (args . length != 1)
        {
            System.out . println ("usage: parseHtml <url>");
            return;
        }
        HtmlParser hp = new HtmlParser
        (
            new UnlimitedPushbackReader
            (
                new InputStreamReader
                (
                    new UrlInputStream (args [0])
                )
            )
        );
        ParallelColumnsWriter pcw = new ParallelColumnsWriter
        (
            new OutputStreamWriter (System.out),
            new int[] {15, 60}
        );
        while (true)
        {
            HtmlComponent c = hp . parse ();
            if (c == null)
                break;
            String clname = c . getClass () . getName ();
            clname = clname . substring (clname . lastIndexOf ('.') + 1);
            pcw . writeln
            (
                new String[]
                {
                    clname,
                    StringEncoder.encodeAsciiJavaString (c . getSource ())
                }
            );
        }
        pcw . close ();
        hp . close ();
    }



}

Click here to download source.

Changes:

2002.04.18

Values in name=value pairs may be enclosed in single quotes.

2000.12.21

Added peek ().

Version:

2002.04.18

See Also:

HtmlComponent, HtmlText, HtmlRegularTag, HtmlOpenTag, HtmlCloseTag, HtmlSpecialTag, HtmlComment, HtmlError

Constructor Summary

HtmlParser(java.io.PushbackReader in)
Sets HTML source.

Method Summary

void	close() Closes source input stream.
static boolean	isCloseTag(HtmlComponent c, java.lang.String type)
static boolean	isOpenTag(HtmlComponent c, java.lang.String type)
HtmlComponent	parse() Parses one HTML element.
HtmlComponent	peek() Peeks at next component without consuming.

Methods inherited from class java.lang.Object

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

Constructor Detail

HtmlParser

public HtmlParser(java.io.PushbackReader in)

Sets HTML source.

Details: This constructor sets the PushbackReader from which this HtmlParser reads.

Parameters:

in - the InputStream

Method Detail

parse

public HtmlComponent parse()
                    throws java.io.IOException

Parses one HTML element.

Details: This method parses one element from the HTML source stream and returns it. Use the instanceof operator to determine the type of element that was parsed. parse returns null if no more elements can be parsed.

Returns:

the parsed element

Throws:

java.io.IOException - if the source stream cannot be read

peek

public HtmlComponent peek()
                   throws java.io.IOException

Peeks at next component without consuming.

Details: This method determines the next component without consuming it. The object returned by this method is the same physical object that will be returned by parse the next time it is called.

Returns:

the next component

Throws:

java.io.IOException - if an I/O error occurs

Since:

2000.12.21

close

public void close()
           throws java.io.IOException

Closes source input stream.

Details: This method closes the HTML source input stream. Of course, no more HTML tokens can be parsed after this method is called.

Throws:

java.io.IOException - if an I/O error occurs

isOpenTag

public static boolean isOpenTag(HtmlComponent c,
                                java.lang.String type)

isCloseTag

public static boolean isCloseTag(HtmlComponent c,
                                 java.lang.String type)