Web Services

WEB SERVICES

Technologies Covered…   

Web Services J2EE .NET

What Is a Web Service?   

Remote access to Data and Process Reusable Unit of Business Work The results can be presented in any fashion required HTML, SWING, MFC,WML, XML, etc,

Definition 

“A collection of functions that are packaged as a single entity and published to the network for use by other programs. Web services are building blocks for creating open distributed systems, and allow companies and individuals to quickly and cheaply make their digital assets available worldwide”

Technical Details

Web Services Architecture

Web Services Framework 

Framework can be described in terms of 

What goes “on the wire”: Formats and protocols.



What describes what goes on the wire: Description languages.



What allows us to find these descriptions: Discovery of services.

Service Oriented Architecture. 







Client queries UDDI registry for services either by name, category, identifier or specification. Once located, the client obtains information about the location of a WSDL document from the UDDI registry WSDL document contains information about how to contact web services and format of request messages in XML schema. Client then creates a SOAP message in accordance with XML schema found in WSDL and sends request to the host.

Processes of Web Services

Travel Service Registry

Desktop Computer

Airline Ticket Reservation

Company Rental Car Reservation

Service Requestor

PDA

Travel Reservation Service Provider

Hotel Reservation

Business Case Example Old work flow 2. Employee requests records from the state 1. Insurance claim is entered into system

4. Employee copies records into system

3. State mails records one week later

1. Insurance claim is entered into system

2. System requests records from the state

3. State immediately sends records to system

b Services We

New work flow

Steps in Web Services Usage     

Step1: Developing Web Service Step 2: Describing Web Service Step 3: Publishing Web Service Step 4: Finding a Web Service Step 5: Binding a Web Service

Step1: Developing Web Service Service provider exposes actual service in the Web   

Http & XML interface Developed in Java or C# or VB.NET It can be deployed in either J2EE or .NET

Step 2: Describing Web Service 







Provider Describes service using WSDL – Web Service Description Language An abstract definition of web service endpoints is described using WSDL Web Services Description Language is an XML grammar for describing web services as collections of messageenabled endpoints or ports The association of a concrete protocol and data format specifications constitutes a Binding

Step 3: Publishing Web Service 

Represents a service provider publishing a service to an external repository. 





Once such a service has been exported to a registry, it can then be used by a client.

Service provider publishes services in UDDI ( Universal Description Discovery Integration) – (IBM, Microsoft, HP) UDDI – public registry 

Group of web-based registries (operator Sites) 



Expose information about a business and its technical interface & APIs

JAXR is a Java API for interoperating with multiple registry types

Step 4: Finding a Web Service 





Looking up a service from a repository and returning information about a service, respectively. Information, such as the format of the procedure calls and the address of a service provider, would normally be provided, amongst other details.

Service information in UDDI - Two Types of Search 



Design Time – Service Provider interacts with registry – checks service available Run Time – Service consumer looking for binding info required to invoke service

Step 5: Binding a Web Service 

Service consumer will access – using service info obtained from UDDI



The client binding to an underlying service Then accessing that service to use whatever functionality the service provides.



J2EE 



 

J2EE is a collection of Enterprise Technologies. The Java 2 Platform, Enterprise Edition (J2EE) was designed to simplify complex problems with the development, deployment, and management of multitier enterprise solutions. J2EE is a standard, not a product. The J2EE architecture is based on the Java programming language.

J2EE Technologies           

EJB Java mail RMI-IIOP JNDI JMS JDBC JTA JCA Servlets JSP IDL

Service Definition Interface package hello; import java.rmi.Remote; import java.rmi.RemoteException; public interface HelloIF extends Remote { public String sayHello (String s) throws RemoteException; }

Implementation Class package hello; public class HelloImpl implements HelloIF { public String message ="Hello"; public String sayHello(String s) { return message + s; } }

Building the service 



The service is compiled using the tool wscompile and the configuration file. <service name="MyHelloService" targetNamespace=“New" typeNamespace=“New" packageName="hello">

Deploying the Service 





The service can be deployed using the deploytool provided by the J2EE Application Server. The WSDL file contains the service endpoint and other details. The client Jar file should be developed in order to enable the client to access the server.

Web Service Client import javax.xml.rpc.Stub; public class HelloClient { public static void main(String[] args) { Stub stub = createProxy(); HelloIF hello = (HelloIF)stub; System.out.println(hello.sayHello("Duke!")); } catch (Exception ex) { ex.printStackTrace(); } } private static Stub createProxy() { return (Stub)(new MyHello_Impl().getHelloIFPort()); } }

.NET 



Microsoft.NET is product suite that enables organizations to build smart, enterprise-class web services. .NET is a product strategy, whereas J2EE is a standard to which products are written.

Developing Web Services in .NET 

Web Services are developed using either VB.NET or C# in the following steps 

  

Code the interface and the implementation in a file having extension .asmx (VB.NET or C#) Store the file in a virtual directory of IIS. Access the file via a Web Browser. Compilation and Deployment are done automatically.

Simple Web Service in C# <%@ WebService class="FirstService.Service1" Language="C#"%> using System; using System.Web; using System.Web.Services; namespace FirstService { public class Service1 : System.Web.Services.WebService { [WebMethod] public string HelloWorld() { return "Hello World"; } } }

Simple Web Service in VB.NET

<%@ WebService Class="Hello" %> imports System.Web.Services imports System imports System.Data <WebService(Namespace:="http://localhost/ ")> Public Class Hello <webMethod()> public Function sayHello() as String return "Hello World" End function End Class

Future of Web Services- Personalized Web Services 

Personalization achieved using   







User profiles Monitoring user behavior Devices and context to customize web services for achieving metrics like Quality of Experience

Involve providing and meeting service performance on user side Creation of third party rating agencies – register user experiences Render web services “customer friendly”