A simple Web Service

We are about to create a simple Web Service in Java. The only requirement is Java SE 6.

At first, we clearly define the operation to be exposed.

public interface SimpleService {
   String sayHello();
}

Let’s declare it as a web service.

@WebService
@SOAPBinding(style=Style.RPC)
public interface SimpleService {
   @WebMethod
   String sayHello();
}

API: WebService, WebMethod, SOAPBinding, SOAPBinding.Style

So we have a web service with a single operation: sayHello. Moreover we choose the simplified RPC style. Let’s implement the operation.

public class SimpleServiceImpl implements SimpleService {
   public String sayHello() {
      return "Hello from Web Services!";
   }
}

We should provide the complete name of the service interface,

@WebService(endpointInterface="simple.SimpleService")
public class SimpleServiceImpl implements SimpleService {
   public String sayHello() {
      return "Hello from Web Services!";
   }
}

where simple is the package of SimpleService.

At this point, it is easy to publish the web service locally.

public class SimpleServicePublisher {
   /**
    * Publishes a Web Service locally.
    */
   public static void main(String[] args) {
      Endpoint.publish("http://127.0.0.1:9000/simple", new SimpleServiceImpl());
   }
}

API: Endpoint

Click on this link to test it: http://127.0.0.1:9000/simple?wsdl.
You will see an XML document in your browser. It is the notorious WSDL, the contract that describes in detail the available operations of our Web Service. Since it is language-neutral, we may built a client in any programming language.

In order to make a Java client, we first need to specify the URL.

URL url = new URL("http://127.0.0.1:9000/simple");

Then we need to specify the qualified namespace that consists of two things:

1. The URI is the value of the @namespace attribute in WSDL.
2. The local part is the value of the service[@name] attribute at the bottom of WSDL.

QName name = new QName("http://simple/", "SimpleServiceImplService");

Now we can create the service,

Service service = Service.create(url, name);

get our port,

SimpleService simple = service.getPort(SimpleService.class);

and interact with our Web Service. The complete code of the client follows.

public class SimpleServiceClient {
   /**
    * Connects to a Web Service.
    */
   public static void main(String[] args) throws Exception {
      // Specify the URL
      final URL url = new URL("http://127.0.0.1:9000/simple");
      // Specify the qualified name
      final QName name = new QName("http://simple/", "SimpleServiceImplService");
      // Create the service
      final Service service = Service.create(url, name);
      // Get the port
      final SimpleService simple = service.getPort(SimpleService.class);
      // Call an operation
      System.out.println(simple.sayHello());
   }
}

API: URL, QName, Service

Summary

The following classes are involved.

• SimpleService and SimpleServiceImpl define the functionality that will be exposed as a Web Service.
• SimpleServicePublisher publishes the Web Service locally.
• SimpleServiceClient is a client of the Web Service.

Thanks.

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