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<!-- author cam@mcc.id.au                                                      -->
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<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V2.0//EN" "http://forrest.apache.org/dtd/document-v20.dtd">
<document>
  <header>
    <title>Parser module</title>
  </header>

  <body>
    <p>
      SVG has a number of microsyntaxes that are used within attribute values,
      such as the <code>transform</code> attribute on
      <code>SVGTransformable</code> elements, and the path data <code>d</code>
      attribute on <code>path</code> elements.  Since these are not trivial to
      parse, this functionality has been factored out into a separate package
      that can be used by other SVG-processing applications if needed.
    </p>

    <section id="parsersHandlersAndProducers">
      <title>Parsers, handlers and producers</title>

      <p>
        In the parser module, each microsyntax is supported by a pair of classes:
        a parser and a handler.  The parser is a class that implements the
        <a class="class" href="../javadoc/org/apache/batik/parser/Parser.html">Parser</a>
        interface, which has methods to parse values from a
        <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/Reader.html">Reader</a>
        or a 
        <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/lang/String.html">String</a>.
        The handler is an interface specific to the microsyntax that will have
        its methods called whenever the corresponding element in the input is
        parsed.  For those handler interfaces that have more than one method,
        adapter classes are provided (named <code>Default</code>*).
      </p>
      <p>
        Parsers can also have an error handler associated with them, whose
        single method <code>error</code> will be called when there is a
        problem parsing the input.  If an error handler is not associated with
        a parser, a
        <a class="class" href="../javadoc/org/apache/batik/parser/ParseException.html">ParseException</a>
        will be thrown if an error occurs.
      </p>
      <p>
        The microsyntaxes supported by the parser module are:
      </p>
      <dl>
        <dt>Angles</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/AngleParser.html">AngleParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/AngleHandler.html">AngleHandler</a>.
            This parser is used for parsing angles formed by a floating point
            number followed by <code>deg</code>, <code>grad</code> or
            <code>rad</code>.  It is not currently used by the rest of the Batik
            codebase.
          </p>
        </dd>
        <dt>Clock values</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/ClockParser.html">ClockParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/ClockHandler.html">ClockHandler</a>.
            This parser is used for parsing SMIL
            <a href="http://www.w3.org/TR/smil-animation/#Timing-ClockValueSyntax">clock values</a>.
          </p>
        </dd>
        <dt>Fragment identifiers</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/FragmentIdentifierParser.html">FragmentIdentifierParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/FragmentIdentifierHandler.html">FragmentIdentifierHandler</a>.
            This parser is used for parsing the various formats of
            <a href="http://www.w3.org/TR/SVG11/linking.html#SVGFragmentIdentifiers">fragment
              identifier</a> that SVG allows.
          </p>
        </dd>
        <dt>Lengths</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/LengthParser.html">LengthParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/LengthHandler.html">LengthHandler</a>.
            This parser is used for parsing SVG length values.
          </p>
        </dd>
        <dt>Length lists</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/LengthListParser.html">LengthListParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/LengthListHandler.html">LengthListHandler</a>.
            This parser is used for parsing lists of comma or space separated
            SVG lengths.
          </p>
        </dd>
        <dt>Numbers</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/NumberListParser.html">NumberListParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/NumberListHandler.html">NumberListHandler</a>.
            This parser is used for parsing SVG number values.
          </p>
        </dd>
        <dt>Number lists</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/NumberListParser.html">NumberListParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/NumberListHandler.html">NumberListHandler</a>.
            This parser is used for parsing lists of comma or space separated
            SVG numbers.
          </p>
        </dd>
        <dt>Path data</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/PathParser.html">PathParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/PathHandler.html">PathHandler</a>.
            This parser is used for parsing SVG path data, as found in
            <code>path</code> element <code>d</code> attributes.
          </p>
        </dd>
        <dt>Points</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/PointsParser.html">PointsParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/PointsHandler.html">PointsHandler</a>.
            This parser is used for parsing point lists, as found in
            <code>polygon</code> element <code>points</code> attributes.
          </p>
        </dd>
        <dt>Preserve aspect ratio values</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/PreserveAspectRatioParser.html">PreserveAspectRatioParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/PreserveAspectRatioHandler.html">PreserveAspectRatioHandler</a>.
            This parser is used for parsing the values found in the
            <code>preserveAspectRatio</code> attribute of <code>svg</code>
            elements.
          </p>
        </dd>
        <dt>Transform lists</dt>
        <dd>
          <p>
            Implemented by
            <a class="class" href="../javadoc/org/apache/batik/parser/TransformListParser.html">TransformListParser</a>,
            handled with
            <a class="class" href="../javadoc/org/apache/batik/parser/TransformListHandler.html">TransformListHandler</a>.
            This parser is used for parsing transform lists, as found in the
            <code>transform</code> attribute of any transformable element.
          </p>
        </dd>
      </dl>
      <p>
        Some microsyntaxes also have a corresponding producer class, which is
        an implementation of the handler interface that generates an object
        while parsing.
      </p>
    </section>

    <section id="examples">
      <title>Examples</title>

      <p>
        The following example code demonstrates how to use the parser classes
        to parse a list of points:
      </p>

      <source>import java.awt.geom.Point2D;
import java.util.LinkedList;
import java.util.List;

import org.apache.batik.parser.DefaultPointsHandler;
import org.apache.batik.parser.ParseException;
import org.apache.batik.parser.PointsHandler;
import org.apache.batik.parser.PointsParser;

public class PointsParserExample {

    public List extractPoints(String s) throws ParseException {
        final LinkedList points = new LinkedList();
        PointsParser pp = new PointsParser();
        PointsHandler ph = new DefaultPointsHandler() {
            public void point(float x, float y) throws ParseException {
                Point2D p = new Point2D.Float(x, y);
                points.add(p);
            }
        };
        pp.setPointsHandler(ph);
        pp.parse(s);
        return points;
    }
}</source>

      <p>
        This example uses the
        <a class="class" href="../javadoc/org/apache/batik/parser/AWTTransformProducer.html">AWTTransformProducer</a>
        class to generate an
        <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/awt/geom/AffineTransform.html">AffineTransform</a>
        object from an SVG transform list:
      </p>

      <source>import java.awt.geom.AffineTransform;

import org.apache.batik.parser.AWTTransformProducer;
import org.apache.batik.parser.ParseException;
import org.apache.batik.parser.TransformListParser;

public class TransformParserExample {

    public AffineTransform parseTransformList(String s) throws ParseException {
        TransformListParser p = new TransformListParser();
        AWTTransformProducer tp = new AWTTransformProducer();
        p.setTransformListHandler(tp);
        p.parse(s);
        return tp.getAffineTransform();
    }
}
</source>
    </section>
  </body>
</document>
