Java tutorial
/* * Copyright 2012 University of South Florida * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package edu.usf.cutr.siri; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import java.nio.charset.Charset; import java.util.List; import org.apache.commons.io.FilenameUtils; //SIRI POJO imports import uk.org.siri.siri.AffectedVehicleJourney; import uk.org.siri.siri.MonitoredStopVisit; import uk.org.siri.siri.PtConsequence; import uk.org.siri.siri.PtSituationElement; import uk.org.siri.siri.Siri; import uk.org.siri.siri.SituationExchangeDelivery; import uk.org.siri.siri.SituationRef; import uk.org.siri.siri.StopMonitoringDelivery; import uk.org.siri.siri.VehicleActivity; import uk.org.siri.siri.VehicleMonitoringDelivery; //Jackson XML imports import com.fasterxml.aalto.stax.InputFactoryImpl; import com.fasterxml.aalto.stax.OutputFactoryImpl; import com.fasterxml.jackson.dataformat.xml.JacksonXmlModule; import com.fasterxml.jackson.dataformat.xml.XmlFactory; import com.fasterxml.jackson.dataformat.xml.XmlMapper; //Jackson JSON imports import com.fasterxml.jackson.databind.DeserializationFeature; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.PropertyNamingStrategy; import edu.usf.cutr.siri.util.SiriUtils; /** * This class is an example of parsing a JSON or XML response from a SIRI feed using Jackson * * @author Sean J. Barbeau * */ public class SiriParserJacksonExample { /** * Takes in a path to a JSON or XML file, parses the contents into a Siri object, * and prints out the contents of the Siri object. * * @param args path to the JSON or XML file located on disk */ public static void main(String[] args) { if (args[0] == null) { System.out.println("Proper Usage is: java JacksonSiriParserExample path-to-siri-file-to-parse"); System.exit(0); } try { //Siri object we're going to instantiate based on JSON or XML data Siri siri = null; //Get example JSON or XML from file File file = new File(args[0]); System.out.println("Input file = " + file.getAbsolutePath()); /* * Alternately, instead of passing in a File, a String encoded in JSON or XML can be * passed into Jackson for parsing. Uncomment the below line to read the * JSON or XML into the String. */ //String inputExample = readFile(file); String extension = FilenameUtils.getExtension(args[0]); if (extension.equalsIgnoreCase("json")) { System.out.println("Parsing JSON..."); ObjectMapper mapper = null; try { mapper = (ObjectMapper) SiriUtils.readFromCache(SiriUtils.OBJECT_MAPPER); } catch (Exception e) { System.out.println("Error reading from cache: " + e); } if (mapper == null) { // instantiate ObjectMapper like normal if cache read failed mapper = new ObjectMapper(); //Jackson 2.0 configuration settings mapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true); mapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true); mapper.configure(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true); mapper.configure(DeserializationFeature.USE_JAVA_ARRAY_FOR_JSON_ARRAY, true); mapper.configure(DeserializationFeature.READ_ENUMS_USING_TO_STRING, true); //Tell Jackson to expect the JSON in PascalCase, instead of camelCase mapper.setPropertyNamingStrategy(new PropertyNamingStrategy.PascalCaseStrategy()); } //Deserialize the JSON from the file into the Siri object siri = mapper.readValue(file, Siri.class); /* * Alternately, you can also deserialize the JSON from a String into the Siri object. * Uncomment the below line to parsing the JSON from a String instead of the File. */ //siri = mapper.readValue(inputExample, Siri.class); //Write the ObjectMapper to the cache, to speed up parsing for the next execution SiriUtils.forceCacheWrite(mapper); } if (extension.equalsIgnoreCase("xml")) { System.out.println("Parsing XML..."); //Use Aalto StAX implementation explicitly XmlFactory f = new XmlFactory(new InputFactoryImpl(), new OutputFactoryImpl()); JacksonXmlModule module = new JacksonXmlModule(); /** * Tell Jackson that Lists are using "unwrapped" style (i.e., * there is no wrapper element for list). This fixes the error * "com.fasterxml.jackson.databind.JsonMappingException: Can not * >> instantiate value of type [simple type, class >> * uk.org.siri.siri.VehicleMonitoringDelivery] from JSON String; * no >> single-String constructor/factory method (through * reference chain: >> * uk.org.siri.siri.Siri["ServiceDelivery"]-> * uk.org.siri.siri.ServiceDel >> * ivery["VehicleMonitoringDelivery"])" * * NOTE - This requires Jackson v2.1 */ module.setDefaultUseWrapper(false); /** * Handles "xml:lang" attribute, which is used in SIRI * NaturalLanguage String, and looks like: <Description * xml:lang="EN">b/d 1:00pm until f/n. loc al and express buses * run w/delays & detours. POTUS visit in MANH. Allow additional * travel time Details at www.mta.info</Description> * * Passing "Value" (to match expected name in XML to map, * considering naming strategy) will make things work. This is * since JAXB uses pseudo-property name of "value" for XML Text * segments, whereas Jackson by default uses "" (to avoid name * collisions). * * NOTE - This requires Jackson v2.1 * * NOTE - This still requires a CustomPascalCaseStrategy to * work. Please see the CustomPascalCaseStrategy in this app * that is used below. */ module.setXMLTextElementName("Value"); XmlMapper xmlMapper = null; try { xmlMapper = (XmlMapper) SiriUtils.readFromCache(SiriUtils.XML_MAPPER); } catch (Exception e) { System.out.println("Error reading from cache: " + e); } if (xmlMapper == null) { xmlMapper = new XmlMapper(f, module); xmlMapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true); xmlMapper.configure(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT, true); xmlMapper.configure(DeserializationFeature.USE_JAVA_ARRAY_FOR_JSON_ARRAY, true); xmlMapper.configure(DeserializationFeature.READ_ENUMS_USING_TO_STRING, true); /** * Tell Jackson to expect the XML in PascalCase, instead of camelCase * NOTE: We need the CustomPascalStrategy here to handle XML * namespace attributes such as xml:lang. See the comments in * CustomPascalStrategy for details. */ xmlMapper.setPropertyNamingStrategy(new CustomPascalCaseStrategy()); } //Parse the SIRI XML response siri = xmlMapper.readValue(file, Siri.class); //Write the XmlMapper to the cache, to speed up parsing for the next execution SiriUtils.forceCacheWrite(xmlMapper); } //If we successfully retrieved and parsed JSON or XML, print the contents if (siri != null) { SiriUtils.printContents(siri); } } catch (IOException e) { System.err.println("Error reading or parsing input file: " + e); } } /** * Read in input file to string * @param file file containing the JSON or XML data * @return String representation of the JSON or XML file * @throws IOException */ private static String readFile(File file) throws IOException { FileInputStream stream = new FileInputStream(file); try { FileChannel fc = stream.getChannel(); MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size()); return Charset.defaultCharset().decode(bb).toString(); } finally { stream.close(); } } }