Source Code Cross Referenced for AbstractOpenWebService.java in  » GIS » GeoTools-2.4.1 » org » geotools » data » ows » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » GIS » GeoTools 2.4.1 » org.geotools.data.ows 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         *    GeoTools - OpenSource mapping toolkit
003:         *    http://geotools.org
004:         *    (C) 2004-2006, GeoTools Project Managment Committee (PMC)
005:         *    
006:         *    This library is free software; you can redistribute it and/or
007:         *    modify it under the terms of the GNU Lesser General Public
008:         *    License as published by the Free Software Foundation;
009:         *    version 2.1 of the License.
010:         *
011:         *    This library is distributed in the hope that it will be useful,
012:         *    but WITHOUT ANY WARRANTY; without even the implied warranty of
013:         *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014:         *    Lesser General Public License for more details.
015:         */
016:        package org.geotools.data.ows;
017:
018:        import java.io.BufferedReader;
019:        import java.io.ByteArrayInputStream;
020:        import java.io.ByteArrayOutputStream;
021:        import java.io.IOException;
022:        import java.io.InputStream;
023:        import java.io.InputStreamReader;
024:        import java.io.OutputStream;
025:        import java.io.PrintStream;
026:        import java.net.HttpURLConnection;
027:        import java.net.URL;
028:        import java.util.ArrayList;
029:        import java.util.Iterator;
030:        import java.util.List;
031:        import java.util.logging.Level;
032:        import java.util.logging.Logger;
033:        import java.util.zip.GZIPInputStream;
034:
035:        import org.geotools.ows.ServiceException;
036:
037:        /**
038:         * This abstract class provides a building block for one to implement an 
039:         * Open Web Service (OWS) client. Each OWS is usually defined by an OGC 
040:         * specification, available at <a href="http://www.opengeospatial.org">http://www.opengeospatial.org</a>.
041:         * 
042:         * This class provides version negotiation, Capabilities document retrieval,
043:         * and a request/response infrastructure. Implementing subclasses need to
044:         * provide their own Specifications (representing versions of the OWS to be
045:         * implemented) and their own request/response instances.
046:         * 
047:         * @author Richard Gould
048:         *
049:         */
050:        public abstract class AbstractOpenWebService {
051:            protected final URL serverURL;
052:            protected Capabilities capabilities;
053:
054:            /** Contains the specifications that are to be used with this service */
055:            protected Specification[] specs;
056:            protected Specification specification;
057:
058:            private static final Logger LOGGER = org.geotools.util.logging.Logging
059:                    .getLogger("org.geotools.data.ows");
060:
061:            /**
062:             * Set up the specifications used and retrieve the Capabilities document
063:             * given by serverURL.
064:             * 
065:             * @param serverURL a URL that points to the capabilities document of a server
066:             * @throws IOException if there is an error communicating with the server
067:             * @throws ServiceException if the server responds with an error
068:             */
069:            public AbstractOpenWebService(final URL serverURL)
070:                    throws IOException, ServiceException {
071:                if (serverURL == null) {
072:                    throw new NullPointerException("ServerURL cannot be null");
073:                }
074:
075:                this .serverURL = serverURL;
076:
077:                setupSpecifications();
078:
079:                capabilities = negotiateVersion();
080:                if (capabilities == null) {
081:                    throw new ServiceException(
082:                            "Unable to retrieve or parse Capabilities document.");
083:                }
084:            }
085:
086:            public AbstractOpenWebService(Capabilities capabilties,
087:                    URL serverURL) {
088:                if (capabilties == null) {
089:                    throw new NullPointerException(
090:                            "Capabilities cannot be null.");
091:                }
092:
093:                if (serverURL == null) {
094:                    throw new NullPointerException("ServerURL cannot be null");
095:                }
096:
097:                setupSpecifications();
098:
099:                for (int i = 0; i < specs.length; i++) {
100:                    if (specs[i].getVersion().equals(capabilties.getVersion())) {
101:                        specification = specs[i];
102:                        break;
103:                    }
104:                }
105:
106:                if (specification == null) {
107:                    specification = specs[specs.length - 1];
108:                    LOGGER
109:                            .warning("Unable to choose a specification based on cached capabilities. "
110:                                    + "Arbitrarily choosing spec '"
111:                                    + specification.getVersion() + "'.");
112:                }
113:
114:                this .serverURL = serverURL;
115:                this .capabilities = capabilties;
116:            }
117:
118:            /**
119:             * Sets up the specifications/versions that this server is capable of
120:             * communicating with.
121:             */
122:            protected abstract void setupSpecifications();
123:
124:            /**
125:             * <p>
126:             * Version number negotiation occurs as follows (credit OGC):
127:             * <ul>
128:             * <li><b>1) </b> If the server implements the requested version number, the server shall send that version.</li>
129:             * <li><b>2a) </b> If a version unknown to the server is requested, the server shall send the highest version less
130:             * than the requested version.</li>
131:             * <li><b>2b) </b> If the client request is for a version lower than any of those known to the server, then the
132:             * server shall send the lowest version it knows.</li>
133:             * <li><b>3a) </b> If the client does not understand the new version number sent by the server, it may either cease
134:             * communicating with the server or send a new request with a new version number that the client does understand but
135:             * which is less than that sent by the server (if the server had responded with a lower version).</li>
136:             * <li><b>3b) </b> If the server had responded with a higher version (because the request was for a version lower
137:             * than any known to the server), and the client does not understand the proposed higher version, then the client
138:             * may send a new request with a version number higher than that sent by the server.</li>
139:             * </ul>
140:             * </p>
141:             * <p>
142:             * The OGC tells us to repeat this process (or give up). This means we are 
143:             * actually going to come up with a bit of setup cost in figuring out our 
144:             * GetCapabilities request. This means that it is possible that we may make
145:             * multiple requests before being satisfied with a response. 
146:             * 
147:             * Also, if we are unable to parse a given version for some reason, 
148:             * for example, malformed XML, we will request a lower version until
149:             * we have run out of versions to request with. Thus, a server that does
150:             * not play nicely may take some time to parse and might not even 
151:             * succeed.
152:             * 
153:             * @return a capabilities object that represents the Capabilities on the server
154:             * @throws IOException if there is an error communicating with the server, or the XML cannot be parsed
155:             * @throws ServiceException if the server returns a ServiceException
156:             */
157:            protected Capabilities negotiateVersion() throws IOException,
158:                    ServiceException {
159:                List versions = new ArrayList(specs.length);
160:                Exception exception = null;
161:
162:                for (int i = 0; i < specs.length; i++) {
163:                    versions.add(i, specs[i].getVersion());
164:                }
165:
166:                int minClient = 0;
167:                int maxClient = specs.length - 1;
168:
169:                int test = maxClient;
170:
171:                while ((minClient <= test) && (test <= maxClient)) {
172:                    Specification tempSpecification = specs[test];
173:                    String clientVersion = tempSpecification.getVersion();
174:
175:                    GetCapabilitiesRequest request = tempSpecification
176:                            .createGetCapabilitiesRequest(serverURL);
177:
178:                    //Grab document
179:                    Capabilities tempCapabilities;
180:                    try {
181:                        tempCapabilities = issueRequest(request)
182:                                .getCapabilities();
183:                    } catch (ServiceException e) {
184:                        tempCapabilities = null;
185:                        exception = e;
186:                    }
187:
188:                    int compare = -1;
189:                    String serverVersion = clientVersion; //Ignored if caps is null
190:
191:                    if (tempCapabilities != null) {
192:
193:                        serverVersion = tempCapabilities.getVersion();
194:
195:                        compare = serverVersion.compareTo(clientVersion);
196:                    }
197:
198:                    if (compare == 0) {
199:                        //we have an exact match and have capabilities as well!
200:                        this .specification = tempSpecification;
201:
202:                        return tempCapabilities;
203:                    }
204:
205:                    if (tempCapabilities != null
206:                            && versions.contains(serverVersion)) {
207:                        // we can communicate with this server
208:                        int index = versions.indexOf(serverVersion);
209:                        this .specification = specs[index];
210:
211:                        return tempCapabilities;
212:
213:                    } else if (compare < 0) {
214:                        // server responded lower then we asked - and we don't understand.
215:                        maxClient = test - 1; // set current version as limit
216:
217:                        // lets try and go one lower?
218:                        //	           
219:                        clientVersion = before(versions, serverVersion);
220:
221:                        if (clientVersion == null) {
222:                            if (exception != null) {
223:                                if (exception instanceof  ServiceException) {
224:                                    throw (ServiceException) exception;
225:                                }
226:                                IOException e = new IOException(exception
227:                                        .getMessage());
228:                                throw e;
229:                            }
230:                            return null; // do not know any lower version numbers
231:                        }
232:
233:                        test = versions.indexOf(clientVersion);
234:                    } else {
235:                        // server responsed higher than we asked - and we don't understand
236:                        minClient = test + 1; // set current version as lower limit
237:
238:                        // lets try and go one higher
239:                        clientVersion = after(versions, serverVersion);
240:
241:                        if (clientVersion == null) {
242:                            if (exception != null) {
243:                                if (exception instanceof  ServiceException) {
244:                                    throw (ServiceException) exception;
245:                                }
246:                                IOException e = new IOException(exception
247:                                        .getMessage());
248:                                throw e;
249:                            }
250:                            return null; // do not know any lower version numbers
251:                        }
252:
253:                        test = versions.indexOf(clientVersion);
254:                    }
255:                }
256:
257:                // could not talk to this server
258:                if (exception != null) {
259:                    IOException e = new IOException(exception.getMessage());
260:                    throw e;
261:                }
262:                return null;
263:            }
264:
265:            /**
266:             * Utility method returning the known version, just before the provided version
267:             * 
268:             * @param known List<String> of all known versions
269:             * @param version the boundary condition
270:             * @return the version just below the provided boundary version
271:             */
272:            String before(List known, String version) {
273:                if (known.isEmpty()) {
274:                    return null;
275:                }
276:
277:                String before = null;
278:
279:                for (Iterator i = known.iterator(); i.hasNext();) {
280:                    String test = (String) i.next();
281:
282:                    if (test.compareTo(version) < 0) {
283:
284:                        if ((before == null) || (before.compareTo(test) < 0)) {
285:                            before = test;
286:                        }
287:                    }
288:                }
289:
290:                return before;
291:            }
292:
293:            /**
294:             * Utility method returning the known version, just after the provided version
295:             * 
296:             * @param known a List<String> of all known versions
297:             * @param version the boundary condition
298:             * @return a version just after the provided boundary condition
299:             */
300:            String after(List known, String version) {
301:                if (known.isEmpty()) {
302:                    return null;
303:                }
304:
305:                String after = null;
306:
307:                for (Iterator i = known.iterator(); i.hasNext();) {
308:                    String test = (String) i.next();
309:
310:                    if (test.compareTo(version) > 0) {
311:                        if ((after == null) || (after.compareTo(test) < 0)) {
312:                            after = test;
313:                        }
314:                    }
315:                }
316:
317:                return after;
318:            }
319:
320:            /**
321:             * Issues a request to the server and returns that server's response. It
322:             * asks the server to send the response gzipped to provide a faster transfer
323:             * time. 
324:             * 
325:             * @param request the request to be issued
326:             * @return a response from the server, which is created according to the specific Request
327:             * @throws IOException if there was a problem communicating with the server
328:             * @throws ServiceException if the server responds with an exception or returns bad content
329:             */
330:            protected Response internalIssueRequest(Request request)
331:                    throws IOException, ServiceException {
332:                URL finalURL = request.getFinalURL();
333:
334:                HttpURLConnection connection = (HttpURLConnection) finalURL
335:                        .openConnection();
336:
337:                connection.addRequestProperty("Accept-Encoding", "gzip");
338:
339:                if (request.requiresPost()) {
340:                    connection.setRequestMethod("POST");
341:                    connection.setDoOutput(true);
342:                    connection.setRequestProperty("Content-type", request
343:                            .getPostContentType());
344:
345:                    OutputStream outputStream = connection.getOutputStream();
346:
347:                    if (LOGGER.isLoggable(Level.FINE)) {
348:                        ByteArrayOutputStream out = new ByteArrayOutputStream();
349:                        request.performPostOutput(out);
350:
351:                        InputStream in = new ByteArrayInputStream(out
352:                                .toByteArray());
353:                        BufferedReader reader = new BufferedReader(
354:                                new InputStreamReader(in));
355:
356:                        PrintStream stream = new PrintStream(outputStream);
357:
358:                        String postText = "";
359:
360:                        while (reader.ready()) {
361:                            String input = reader.readLine();
362:                            postText = postText + input;
363:                            stream.println(input);
364:                        }
365:                        LOGGER.fine(postText);
366:                        System.out.println(postText);
367:
368:                        out.close();
369:                        in.close();
370:                    } else {
371:                        request.performPostOutput(outputStream);
372:                    }
373:
374:                    outputStream.flush();
375:                    outputStream.close();
376:                } else {
377:                    connection.setRequestMethod("GET");
378:                }
379:
380:                InputStream inputStream = connection.getInputStream();
381:
382:                if (connection.getContentEncoding() != null
383:                        && connection.getContentEncoding().indexOf("gzip") != -1) { //$NON-NLS-1$
384:                    inputStream = new GZIPInputStream(inputStream);
385:                }
386:
387:                String contentType = connection.getContentType();
388:
389:                return request.createResponse(contentType, inputStream);
390:            }
391:
392:            public GetCapabilitiesResponse issueRequest(
393:                    GetCapabilitiesRequest request) throws IOException,
394:                    ServiceException {
395:                return (GetCapabilitiesResponse) internalIssueRequest(request);
396:            }
397:
398:            public void setLoggingLevel(Level newLevel) {
399:                LOGGER.setLevel(newLevel);
400:            }
401:        }
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