Class GMLHandler

1	/*
2	* Copyright (c) 2016 Vivid Solutions.
3	*
4	* All rights reserved. This program and the accompanying materials
5	* are made available under the terms of the Eclipse Public License 2.0
6	* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
7	* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
8	* and the Eclipse Distribution License is available at
9	*
10	* http://www.eclipse.org/org/documents/edl-v10.php.
11	*/
12	package org.locationtech.jts.io.gml2;
13
14	import java.util.LinkedList;
15	import java.util.List;
16	import java.util.Stack;
17
18	import org.locationtech.jts.geom.Geometry;
19	import org.locationtech.jts.geom.GeometryFactory;
20	import org.locationtech.jts.io.gml2.GeometryStrategies.ParseStrategy;
21	import org.xml.sax.Attributes;
22	import org.xml.sax.ContentHandler;
23	import org.xml.sax.ErrorHandler;
24	import org.xml.sax.Locator;
25	import org.xml.sax.SAXException;
26	import org.xml.sax.SAXParseException;
27	import org.xml.sax.helpers.AttributesImpl;
28	import org.xml.sax.helpers.DefaultHandler;
29
30
31	/**
32	* A SAX {@link DefaultHandler} which builds {@link Geometry}s
33	* from GML2-formatted geometries.
34	* An XML parser can delegate SAX events to this handler
35	* to parse and building Geometrys.
36	* <p>
37	* This handler currently ignores both namespaces and prefixes.
38	*
39	* Hints:
40	* <ul>
41	* <li>If your parent handler is a DefaultHandler register the parent handler to receive the errors and locator calls.
42	* <li>Use {@link GeometryStrategies#findStrategy(String, String)} to help check for applicability
43	* </ul>
44	*
45	* @see DefaultHandler
46	*
47	* @author David Zwiers, Vivid Solutions.
48	*/
49	public class GMLHandler extends DefaultHandler {
50
51	/**
52	* This class is intended to log the SAX activity within a given element until its termination.
53	* At this time, a new object of value is created and passed to the parent.
54	* An object of value is typically either java.lang.* or a JTS Geometry
55	* This class is not intended for use outside this distribution,
56	* and may change in subsequent versions.
57	*
58	* @author David Zwiers, Vivid Solutions.
59	*/
60	static class Handler {
61	protected Attributes attrs = null;
62
63	protected ParseStrategy strategy;
64
65	/**
66	* @param strategy
67	* @param attributes Nullable
68	*/
69	public Handler(ParseStrategy strategy, Attributes attributes) {
70	if (attributes != null)
71	this.attrs = new AttributesImpl(attributes);
72	this.strategy = strategy;
73	}
74
75	protected StringBuffer text = null;
76
77	/**
78	* Caches text for the future
79	* @param str
80	*/
81	public void addText(String str) {
82	if (text == null)
83	text = new StringBuffer();
84	text.append(str);
85	}
86
87	protected List children = null;
88
89	/**
90	* Store param for the future
91	*
92	* @param obj
93	*/
94	public void keep(Object obj) {
95	if (children == null)
96	children = new LinkedList();
97	children.add(obj);
98
99	}
100
101	/**
102	* @param gf GeometryFactory
103	* @return Parsed Object
104	* @throws SAXException
105	*/
106	public Object create(GeometryFactory gf) throws SAXException {
107	return strategy.parse(this, gf);
108	}
109	}
110
111	private Stack stack = new Stack();
112
113	private ErrorHandler delegate = null;
114
115	private GeometryFactory gf = null;
116
117	/**
118	* Creates a new handler.
119	* Allows the user to specify a delegate object for error / warning messages.
120	* If the delegate also implements ContentHandler then the document Locator will be passed on.
121	*
122	* @param gf Geometry Factory
123	* @param delegate Nullable
124	*
125	* @see ErrorHandler
126	* @see ContentHandler
127	* @see ContentHandler#setDocumentLocator(org.xml.sax.Locator)
128	* @see org.xml.sax.Locator
129	*
130	*/
131	public GMLHandler(GeometryFactory gf, ErrorHandler delegate) {
132	this.delegate = delegate;
133	this.gf = gf;
134	stack.push(new Handler(null, null));
135	}
136
137	/**
138	* Tests whether this handler has completed parsing
139	* a geometry.
140	* If this is the case, {@link #getGeometry()} can be called
141	* to get the value of the parsed geometry.
142	*
143	* @return if the parsing of the geometry is complete
144	*/
145	public boolean isGeometryComplete()
146	{
147	if (stack.size() > 1)
148	return false;
149	// top level node on stack needs to have at least one child
150	Handler h = (Handler) stack.peek();
151	if (h.children.size() < 1)
152	return false;
153	return true;
154
155	}
156
157	/**
158	* Gets the geometry parsed by this handler.
159	* This method should only be called AFTER the parser has completed execution
160	*
161	* @return the parsed Geometry, or a GeometryCollection if more than one geometry was parsed
162	* @throws IllegalStateException if called before the parse is complete
163	*/
164	public Geometry getGeometry() {
165	if (stack.size() == 1) {
166	Handler h = (Handler) stack.peek();
167	if (h.children.size() == 1)
168	return (Geometry) h.children.get(0);
169	return gf.createGeometryCollection(
170	(Geometry[]) h.children.toArray(new Geometry[stack.size()]));
171	}
172	throw new IllegalStateException(
173	"Parse did not complete as expected, there are " + stack.size()
174	+ " elements on the Stack");
175	}
176
177	//////////////////////////////////////////////
178	// Parsing Methods
179
180	/**
181	* @see org.xml.sax.helpers.DefaultHandler#characters(char[], int, int)
182	*/
183	public void characters(char[] ch, int start, int length) throws SAXException {
184	if (!stack.isEmpty())
185	((Handler) stack.peek()).addText(new String(ch, start, length));
186	}
187
188	/**
189	* @see org.xml.sax.helpers.DefaultHandler#ignorableWhitespace(char[], int, int)
190	*/
191	public void ignorableWhitespace(char[] ch, int start, int length)
192	throws SAXException {
193	if (!stack.isEmpty())
194	((Handler) stack.peek()).addText(" ");
195	}
196
197	/**
198	* @see org.xml.sax.helpers.DefaultHandler#endElement(java.lang.String, java.lang.String, java.lang.String)
199	*/
200	public void endElement(String uri, String localName, String qName)
201	throws SAXException {
202	Handler thisAction = (Handler) stack.pop();
203	((Handler) stack.peek()).keep(thisAction.create(gf));
204	}
205
206	/**
207	* @see org.xml.sax.helpers.DefaultHandler#startElement(java.lang.String, java.lang.String, java.lang.String, org.xml.sax.Attributes)
208	*/
209	public void startElement(String uri, String localName, String qName,
210	Attributes attributes) throws SAXException {
211	// create a handler
212	ParseStrategy ps = GeometryStrategies.findStrategy(uri, localName);
213	if (ps == null) {
214	String qn = qName.substring(qName.indexOf(':') + 1, qName.length());
215	ps = GeometryStrategies.findStrategy(null, qn);
216	}
217	Handler h = new Handler(ps, attributes);
218	// and add it to the stack
219	stack.push(h);
220	}
221
222	//////////////////////////////////////////////
223	// Logging Methods
224
225	/**
226	* @see org.xml.sax.helpers.DefaultHandler#setDocumentLocator(org.xml.sax.Locator)
227	*/
228	public void setDocumentLocator(Locator locator) {
229	this.locator = locator;
230	if (delegate != null && delegate instanceof ContentHandler)
231	((ContentHandler) delegate).setDocumentLocator(locator);
232
233	}
234
235	private Locator locator = null;
236
237	protected Locator getDocumentLocator() {
238	return locator;
239	}
240
241	//////////////////////////////////////////////
242	// ERROR Methods
243
244	/**
245	* @see org.xml.sax.helpers.DefaultHandler#fatalError(org.xml.sax.SAXParseException)
246	*/
247	public void fatalError(SAXParseException e) throws SAXException {
248	if (delegate != null)
249	delegate.fatalError(e);
250	else
251	super.fatalError(e);
252	}
253
254	/**
255	* @see org.xml.sax.helpers.DefaultHandler#error(org.xml.sax.SAXParseException)
256	*/
257	public void error(SAXParseException e) throws SAXException {
258	if (delegate != null)
259	delegate.error(e);
260	else
261	super.error(e);
262	}
263
264	/**
265	* @see org.xml.sax.helpers.DefaultHandler#warning(org.xml.sax.SAXParseException)
266	*/
267	public void warning(SAXParseException e) throws SAXException {
268	if (delegate != null)
269	delegate.warning(e);
270	else
271	super.warning(e);
272	}
273
274	}
275