Application: gvSIG desktop

/*

 * The JTS Topology Suite is a collection of Java classes that

 * implement the fundamental operations required to validate a given

 * geo-spatial data set to a known topological specification.

 *

 * Copyright (C) 2001 Vivid Solutions

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * For more information, contact:

 *

 *     Vivid Solutions

 *     Suite #1A

 *     2328 Government Street

 *     Victoria BC  V8T 5G5

 *     Canada

 *

 *     (250)385-6040

 *     www.vividsolutions.com

 */

package org.gvsig.fmap.geom.jts.gml;

import com.vividsolutions.jts.geom.Geometry;

import com.vividsolutions.jts.geom.GeometryFactory;

import java.util.*;

import org.gvsig.fmap.geom.jts.gml.GeometryStrategies.ParseStrategy;

import org.xml.sax.*;

import org.xml.sax.helpers.AttributesImpl;

import org.xml.sax.helpers.DefaultHandler;

/**

 * A SAX {@link DefaultHandler} which builds {@link Geometry}s 

 * from GML2-formatted geometries.

 * An XML parser can delegate SAX events to this handler

 * to parse and building Geometrys. 

 * <p>

 * This handler currently ignores both namespaces and prefixes. 

 * 

 * Hints: 

 * <ul>

 * <li>If your parent handler is a DefaultHandler register the parent handler to receive the errors and locator calls.

 * <li>Use {@link GeometryStrategies#findStrategy(String, String)} to help check for applicability

 * </ul>

 * 

 * @see DefaultHandler

 *

 * @author David Zwiers, Vivid Solutions. 

 */

public class GMLHandler extends DefaultHandler {

        /**

         * This class is intended to log the SAX acitivity within a given element until its termination. 

         * At this time, a new object of value is created and passed to the parent. 

         * An object of value is typically either java.lang.* or a JTS Geometry

         * This class is not intended for use outside this distribution, 

         * and may change in subsequent versions.

         *

         * @author David Zwiers, Vivid Solutions.

         */

        static class Handler {

                protected Attributes attrs = null;

                protected ParseStrategy strategy;

                /**

                 * @param strategy 

                 * @param attributes Nullable

                 */

                public Handler(ParseStrategy strategy, Attributes attributes) {

                        if (attributes != null)

                                this.attrs = new AttributesImpl(attributes);

                        this.strategy = strategy;

                }

                protected StringBuffer text = null;

                /**

                 * Caches text for the future

                 * @param str

                 */

                public void addText(String str) {

                        if (text == null)

                                text = new StringBuffer();

                        text.append(str);

                }

                protected List children = null;

                /**

                 * Store param for the future

                 * 

                 * @param obj

                 */

                public void keep(Object obj) {

                        if (children == null)

                                children = new LinkedList();

                        children.add(obj);

                }

                /**

                 * @param gf GeometryFactory

                 * @return Parsed Object

                 * @throws SAXException 

                 */

                public Object create(GeometryFactory gf) throws SAXException {

//                    System.out.println("create "+this.strategy.getClass().getSimpleName());

                    return strategy.parse(this, gf);

                }

        }

        private Stack stack = new Stack();

        private ErrorHandler delegate = null;

        private GeometryFactory gf = null;

        /**

         * Creates a new handler.

         * Allows the user to specify a delegate object for error / warning messages. 

         * If the delegate also implements ContentHandler then the document Locator will be passed on.

         * 

         * @param gf Geometry Factory

         * @param delegate Nullable

         * 

         * @see ErrorHandler

         * @see ContentHandler

         * @see ContentHandler#setDocumentLocator(org.xml.sax.Locator)

         * @see org.xml.sax.Locator

         * 

         */

        public GMLHandler(GeometryFactory gf, ErrorHandler delegate) {

                this.delegate = delegate;

                this.gf = gf;

                stack.push(new Handler(null, null));

        }

        /**

         * Tests whether this handler has completed parsing 

         * a geometry.

         * If this is the case, {@link #getGeometry()} can be called

         * to get the value of the parsed geometry.

         * 

         * @return if the parsing of the geometry is complete

         */

        public boolean isGeometryComplete()

        {

                if (stack.size() > 1)

                        return false;

                // top level node on stack needs to have at least one child 

                Handler h = (Handler) stack.peek();

                if (h.children.size() < 1)

                        return false;

                return true;

        }

        /**

         * Gets the geometry parsed by this handler.

         * This method should only be called AFTER the parser has completed execution

         * 

         * @return the parsed Geometry, or a GeometryCollection if more than one geometry was parsed

         * @throws IllegalStateException if called before the parse is complete

         */

        public Geometry getGeometry() {

                if (stack.size() == 1) {

                        Handler h = (Handler) stack.peek();

                        if (h.children.size() == 1)

                                return (Geometry) h.children.get(0);

                        return gf.createGeometryCollection(

                                        (Geometry[]) h.children.toArray(new Geometry[stack.size()]));

                }

                throw new IllegalStateException(

                                "Parse did not complete as expected, there are " + stack.size()

                                                + " elements on the Stack");

        }

        //////////////////////////////////////////////

        // Parsing Methods

        /**

         * @see org.xml.sax.helpers.DefaultHandler#characters(char[], int, int)

         */

        public void characters(char[] ch, int start, int length) throws SAXException {

                if (!stack.isEmpty())

                        ((Handler) stack.peek()).addText(new String(ch, start, length));

        }

        /**

         * @see org.xml.sax.helpers.DefaultHandler#ignorableWhitespace(char[], int, int)

         */

        public void ignorableWhitespace(char[] ch, int start, int length)

                        throws SAXException {

                if (!stack.isEmpty())

                        ((Handler) stack.peek()).addText(" ");

        }

        /**

         * @see org.xml.sax.helpers.DefaultHandler#endElement(java.lang.String, java.lang.String, java.lang.String)

         */

        public void endElement(String uri, String localName, String qName)

                        throws SAXException {

//            System.out.println("endElement: "+localName +" , "+qName);

                Handler thisAction = (Handler) stack.pop();

                ((Handler) stack.peek()).keep(thisAction.create(gf));

        }

        /**

         * @see org.xml.sax.helpers.DefaultHandler#startElement(java.lang.String, java.lang.String, java.lang.String, org.xml.sax.Attributes)

         */

        public void startElement(String uri, String localName, String qName,

                        Attributes attributes) throws SAXException {

//            System.out.println("startElement: "+localName +" , "+qName);

                // create a handler

                ParseStrategy ps = GeometryStrategies.findStrategy(uri, localName);

                if (ps == null) {

                        String qn = qName.substring(qName.indexOf(':') + 1, qName.length());

                        ps = GeometryStrategies.findStrategy(null, qn);

                }

                Handler h = new Handler(ps, attributes);

                // and add it to the stack

                stack.push(h);

        }

        //////////////////////////////////////////////

        // Logging Methods

        /**

         * @see org.xml.sax.helpers.DefaultHandler#setDocumentLocator(org.xml.sax.Locator)

         */

        public void setDocumentLocator(Locator locator) {

                this.locator = locator;

                if (delegate != null && delegate instanceof ContentHandler)

                        ((ContentHandler) delegate).setDocumentLocator(locator);

        }

        private Locator locator = null;

        protected Locator getDocumentLocator() {

                return locator;

        }

        //////////////////////////////////////////////

        // ERROR Methods

        /**

         * @see org.xml.sax.helpers.DefaultHandler#fatalError(org.xml.sax.SAXParseException)

         */

        public void fatalError(SAXParseException e) throws SAXException {

                if (delegate != null)

                        delegate.fatalError(e);

                else

                        super.fatalError(e);

        }

        /**

         * @see org.xml.sax.helpers.DefaultHandler#error(org.xml.sax.SAXParseException)

         */

        public void error(SAXParseException e) throws SAXException {

                if (delegate != null)

                        delegate.error(e);

                else

                        super.error(e);

        }

        /**

         * @see org.xml.sax.helpers.DefaultHandler#warning(org.xml.sax.SAXParseException)

         */

        public void warning(SAXParseException e) throws SAXException {

                if (delegate != null)

                        delegate.warning(e);

                else

                        super.warning(e);

        }

}