How to Write RESTful Web Services With JAX-WS

Web Development Full Course for Beginners

How to get a source type from a StringBuffer

return new StreamSource( new StringReader(text.toString()) );

The above line will return a StreamSource from a StringBuffer instance text.

We are all done with the weather service. Now let’s publish the service.

WeatherPublisher.java

import javax.xml.ws.Endpoint;

public class WeatherPublisher {

	public static void main(String[] args) {
		System.out.println("Publishing Weather Service");
		Endpoint.publish("http://127.0.0.1:8700/weather",new RESTfulWeather());

	}
}

Accessing the Web Service

Let’s access the weather service giving it a city name. We can check the weather for Seoul

We get an XML document as the response with information on latitude, longitude, temperature, humidity , wind, clouds etc.

As our weather service is up and running, it’s time to write a client which will use this service.

Writing a client against weather service

Since weather service returns an XML document as a response, any client that uses the web service will have to parse that XML document. Below is the Java client written against the weather service

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class WeatherClient {

	public static void main(String[] args) throws IOException, SAXException, ParserConfigurationException {
		// GET requests
		URL url=new URL("http://127.0.0.1:8700/weather?city=seoul");		
		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
		conn.setRequestMethod("GET");
		conn.connect();		

		String xml = "";
		BufferedReader reader =	new BufferedReader(new InputStreamReader(conn.getInputStream()));
		String next = null;
		while ((next = reader.readLine()) != null)
		xml += next;		

		SAXParser parser =SAXParserFactory.newInstance().newSAXParser();
		SaxParserHandler handler=new SaxParserHandler();
		parser.parse(new ByteArrayInputStream(xml.getBytes()),handler);
		System.out.println("-------------------------------------------------------------------");
		System.out.println(handler.city+" weather update on "+handler.lastUpdate);
		System.out.println("-------------------------------------------------------------------");
		System.out.println("City : "+handler.city);
		System.out.println("Latitude : "+handler.latitude);
		System.out.println("Longitude : "+handler.longitude);
		System.out.println("Mininum Temperature (Celsius) : "+handler.minTemperature);
		System.out.println("Maximum Temperature (Celsius) : "+handler.maxTemperature);
		System.out.println("Wind : "+handler.wind);
		System.out.println("Clouds : "+handler.clouds);
	}
}	

    class SaxParserHandler extends DefaultHandler{
		 String city;
		 String latitude;
		 String longitude;
		 float minTemperature;
		 float maxTemperature;
		 String wind;
		 String clouds;
		 String lastUpdate;

		 public void startElement(String namespaceURI,String localName,String qname,Attributes attributes){		

				if(qname.equals("city")){
					city=attributes.getValue("name");					
				}else if(qname.equals("coord")){
					latitude=attributes.getValue("lat");					
					longitude=attributes.getValue("lon");
				}
				else if(qname.equals("temperature")){
					String minKelvin=attributes.getValue("min");
					minTemperature=Math.round(Float.parseFloat(minKelvin)) - 272;
					String maxKelvin=attributes.getValue("max");					
					maxTemperature=Math.round(Float.parseFloat(maxKelvin)) - 272;
				}
				else if(qname.equals("speed")){
					wind=attributes.getValue("name");										
				}
				else if(qname.equals("clouds")){
					clouds=attributes.getValue("name");									
				}	
				else if(qname.equals("lastupdate")){
					lastUpdate=attributes.getValue("value").split("T")[0];									
				}
			}		

      }

Note : WeatherClient uses SAX parser to parse the response from the service. If you are not very familiar with parsing XML files in Java, here is an article that explains how to parse XML files using SAX parser.

You can also use a DOM or StAX parser for parsing the XML document.

Output

Below is the output that you will get on executing the WeatherClient class

A Word of Caution :

Let’s iterate through what we said earlier, JAX-WS is not the right choice for implementing real-world RESTful services. For writing real-world RESTful web services JAX-RS, Restlet or Spring framework is the way to go.

Curious to try the code yourself? Download the code.

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Getting java.net.BindException: If you are trying to publish the web service on a port that is already in use you will get java.net.BindException

Caused by: java.net.BindException: Address already in use: bind

To get rid of the exception just use some other port for publishing the web service.

Got a question for us? Please mention it in the comments section and we will get back to you.

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