GMLHandler.java
/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.io.gml2;
import java.util.LinkedList;
import java.util.List;
import java.util.Stack;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryFactory;
import org.locationtech.jts.io.gml2.GeometryStrategies.ParseStrategy;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
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 activity 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 {
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 {
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 {
// 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 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);
}
}