Understanding web service in simple words

What is a Web Service ? :

• A webservice is a software function provided at a network address over the web

• It is supposed to be "always on"

• Web services are really nothing more than a request/ response mechanism that allows a client to remotely access/ modify data.

Types of Web Services :

1. Big Web Services  (Basically StateFull)

( JAX-WS provides the functionality for “big” web services )

• Big web services use XML messages that follow the Simple Object Access Protocol (SOAP) standard.

A SOAP-based design must include the following elements.

• A formal contract ,WSDL can be used to describe the details of the contract .

• The architecture must address complex nonfunctional requirements .

Examples include transactions, security, addressing, trust, coordination, and so on. For More on JAX-WS Refer this link 

Basic Component of State Full Webservices

What is WSDL?

•  Web Services Description Language

• based on XML

• describe Web services
• locate Web services

What is SOAP?

• Simple Object Access Protocol

• format for sending messages

• platform independent

• based on XML

What is UDDI?

UDDI is a directory service where companies can register and search for Web services.

 2)  RESTful Web Services (Stateless)

         (  JAX-RS provides the functionality for Representational State Transfer (RESTful) web services  )

         

REST is well suited for basic, ad hoc integration scenarios. RESTful web services, often better integrated with HTTP than SOAP-based services are, do not require XML messages or WSDL service–API definitions .

developing RESTful web services is inexpensive .

Appropriate for  following conditions .

1. The web services are completely stateless (A stateless server is a server that treats each request as an independent transaction that is unrelated to any previous request.) A good test is to consider whether the interaction can survive a restart of the server.

2. A caching infrastructure can be leveraged for performance. If the data that the web service returns is not dynamically generated and can be cached.
3. producer and service consumer have a mutual understanding of the context and content being passed along.

Learn JAX WS in Few Seconds..

Implementing web service Endpoint/Client with JAX WS

Developing Web Service End Point

1) In Eclipse  create a java project "JAXWS-Server".

2) Create JAXWS-Service Endpoint Interface:

--------------------------------------------------------------------------

package mysimple.example.define;

import javax.jws.WebMethod;

import javax.jws.WebService;

@WebService

public interface Greeting {

@WebMethod String sayHello(String name);

}

-------------------------------------------------------------------------- 

3) Create JAXWS-Service Endpoint Implementation class:

-------------------------------------------------------------------------- 

package mysimple.example.define;

import javax.jws.WebService;

@WebService(endpointInterface = "mysimple.example.define.Greeting")

public class GreetingImpl implements Greeting  {

@Override

public String sayHello(String name) {

return "Hello, This is simplest JAX-WS example By :: " + name;

}

}

--------------------------------------------------------------------------  

4) Create Endpoint Publisher class:

-------------------------------------------------------------------------- 

package mysimple.example.publish;

import javax.xml.ws.Endpoint;

import mysimple.example.define.GreetingImpl;

public class WSPublisher {

public static void main(String[] args) {

Endpoint.publish("http://localhost:8080/WS/Greeting",new GreetingImpl());

}

}

-------------------------------------------------------------------------- 

5) Run the WSPublisher….and your WebService is published.

Check the service wsdl http://localhost:8080/WS/Greeting?wsdl

Developing Web Service Client :

1) In eclipse create a new java project JAXWS-Client

2) we need to generate the client stubs by following command(on the src path)

Command : wsimport -keep -verbose http://localhost:8080/WS/Greeting?wsdl

1. Remove all the class files
2. Create the  Client Class which will be dependent on the stubs

-------------------------------------------------------------------------- 

package mysimpleexample.client;

import mysimple.example.define.Greeting;

import mysimple.example.define.GreetingImplService;

public class Client {

public static void main(String[] args){

GreetingImplService service = new GreetingImplService();

Greeting greeting = service.getGreetingImplPort();

System.out.println("------->>  Call Started");

System.out.println(greeting.sayHello("Manish_Kumar_Jaiswal"));

System.out.println("------->>  Call Ended");

}

}

-------------------------------------------------------------------------- 

3. Output :

------->>  Call Started

Hello, This is simplest JAX-WS example By :: Manish_Kumar_Jaiswal

------->>  Call Ended