Web services - A Practical Approach

What is Web Service?
• Services are available in the Web.
• Communication between the two system
over network.
• Software system designed to support
interoperable machine-machine interaction
over the network (w3c definition).
• Real-time Example:
– Facebook, Google, Twitter, e-commerce sites,
and irctc.

Simple Use case
Application Server-1
bookTicket()
IRCTC- Ticket Service
DB
Dealer site1
(makemytrip.com)
Struts
Dealer site2
(cleartrip.com)
.NET/RUBY
cancelTicket()
Interface

Criteria for interface and
request/response
• Interface should be
platform independent. So
what is the format? And
why?
• Request and response
should be language
natural. So what is the
format? And why?

Web Service Terminologies
• SOAP – Simple Object Access Protocol.
– Envelope for soap request/response.
• WSDL – Web Service Description Language.
– Interface for SOAP web service
• UDDI – Universal Description, Discovery and
Integration.
– Repository/yellow pages of web services
• REST – REpresentational State Transfer.
– Architecture style of communication to the services
• HTTP – Hypertext Transfer Protocol.
– Stateless protocol and used for transport

Different Types of Web Services
SOAP REST
JAX-WS standard JAX-RS standard
Required WSDL interface for expos as web
service
No Interface. It uses HTTP methods
(GET,POST,PUT,DELETE)
XML should be communication medium for
request and response
Both XML and JSON used for request
and response.
Maintain session state Stateless (fire and forget)
It uses SOAP protocol to transfer data over
HTTP
Uses only HTTP
Not human readable Human readable
Client – server communication heavy weight
like BLOB
Simple client-server communication
and light weight.

SOAP vs REST
Client ServerData
SOAP
Standard
Huge
Data+ = <=>
SOAP
Client ServerData <=>
Sending data as its
REST
*REST are mostly used in industry

Web service Flow-I
HTTP
HTTP
Web Browser
Mobile
WSDL
SOAP
REST
DB
Web services
Application Server
Not Applicable for Real time
and it FALSE one for SOAP.

Disadvantage of flow-I
• Consuming SOAP services from Java Scripts is
tedious and time consuming task.
• Some browser will not support build in Jquery
functions for SOAP.(Browser compatibility)
• Security validation is needed for every service.
Because anybody can access any service.
• No centralized controlled.
• UI change to be needed for every Web service
enhancements like URL for version update.

Web service Flow-II (Actual)
Web Browser
Mobile
(Toolkit)
Java Web
service Client
DB
WSDL
SOAP
REST
DB
Web Server/application
server
Web/Servlet
application
Web services
Application Server
HTTP
HTTP
Client for Web service
Client for
Web App

Advantage of Flow-II
• Centralized control.
• Only authorized users/vendors can consume
web services.
• No UI changes needed.
• Can use OAUTH/APIGEE for security.
• Standard industry model

Examples
• GeoIP service
– http://www.webservicex.net/ws/WSDetails.aspx?
WSID=64&CATID=12
• One Time Password(OTP) service
– Our own service

Web Service - OTP
• OTP(One-Time-Password) Generator.
– This web service will generate OTP for authentication
for more security.
– Used in banking site, e-commerce site for every
transactions.
• Functionality
– Generate OTP and send to mail.
– Validate OTP.
– Get registered user.
– Get all registered users.

Complete Application architecture
(HealthCare Portal)
Generate OTP
Validate
Get All Subscriber
Get Subscriber
DB
WSDL
SMTP Mail
Server
(GMAIL)
Application Server (Glassfish)
Java
.Net
Ruby
Web Server
(Tomcat)
Servlets
End
User
SOAP Client
JDBC
ORM
(Hibernate)

Setup environments
• Required software
– JDK 1.6
– IDE (Eclipse/NetBeans)
– Application server (GlassFish)
– Mail API
– Database (postgresql DB)
• Technology used
– Java
– XML
– JDBC

Service Development
package com.soapwebtest.service;
import java.util.List;
import java.util.Random;
import javax.jws.WebMethod;
import javax.jws.WebService;
import com.soapwebtest.service.model.Subscriber;
@WebService
public class OTPGenerator {
@WebMethod
public boolean generateOtp(String email) {
return false;
}
public boolean validate(String mail, String otp) {
return false;
}
public Subscriber getSubscriber(String mail) {
return subscriber.
}
public List<Subscriber> getAllSubscriber() {
return List<Subscriber>
}
}

OTP service – WSDL interface

Compare WSDL with java Interface
package com.testapp.webservice //package name
Public interface Calculatore{ //interface name
int add(int a, int b); // method name, input and output parameters
int multiply(int a, int b);
Math add (Math math); //Object
}

WSDL high level elements
-<definition>
+<types> //input and output types reference
+<message> // inputs and outputs (one for input and one for output)
-<portType>
-<operation> //method name of webservice
<input> // all input and output are message
(one for input and one for output)
<output>
</operation>
+<binding> //information about how webservices accepts
its input and output via http (literal via http)
+<service> //list of ports and each port has address location.
port consist of operations
-</definition>

Name Space and types
• Name space represent the package name of
service.
• Name space should be unique.
• Types represents what kind of data type to
passed to service input and output over HTTP.
• Types will be applicable only for document style
binding. Not for RPC.

SOAP binding style
JAX-RPC Document
no XSD XSD document as an input and
output
easy to read complex to read
no validation validates inputs (ex : minoccurs)
Note:
Document style binding is default
SOAP binding represents what kind of communication and data passed to
request and response for the service.

Service, portType and message
• Service consist of ports and each port will
have address location URL.
• portType has operations of service which
exposed on the particular port.
• Each operation has input/output which
represent as messages.

Web service client
• One who consume web service is called web
service client.
• Client needs only WSDL interface.
• Different Types of Clients:
– Java
– .Net
– Ruby
– Python

Steps to create java client
• Use wsimport
– Wsimport –keep –s <src> <wsdl>
• Use Eclipse-IDE
– Create java project.
– Create Web service client.
– Specify the WSDL and Validate.
– Generate required classes using Axis.

Web Service Client Example
package com.soapwebtest.service;
import java.rmi.RemoteException;
import java.util.Arrays;
import java.util.List;
public class OTPClient {
public static void main(String[] args) throws RemoteException {
OTPGenerator service = new OTPGeneratorProxy();
List<Subscriber> ll = Arrays.asList(service.getAllSubscriber());
for (Subscriber subscriber : ll) {
System.out.println(subscriber.getEmail());
}
}
}

Complete Application architecture
(HealthCare Portal)
Generate OTP
Validate
Get All Subscriber
Get Subscriber
DB
WSDL
Mail Server
(GMAIL)
Application Server (Glassfish)
Java
.NET
Ruby
Web Server
(Tomcat)
Servlets
End
User
SOAP Client
JDBC
ORM
(Hibernate)

Developing Web Application and
Integrate SOAP Client
• Required Software:
– Hibernate
– Postgresql(Database)
– Tomcat (web server)
– SOAP Client
• Technology
– HTML
– JSP
– Servlets
– Java
– XML (web.xml)

Tomcat Web Server
Browser
Tomcat
Request
Response
Web Application
Web Application
Web Application
Login Servlet
Web.xml /
annotation

Servlet Terminologies
• Http- Stateless protocol
• HttpRequest – scope will be only on request
• HttpResponse- scope will be only on response
• HttpSession – scope on particular
browser/user
• ServletConfig- Scope on particular servlet
• ServletContext – Scope for all servlet and
every browser/user.

Serialization
• Process of storing object state for streaming
called serialization.
• Every java class should implements
serializable interface
• What is object state?
• Why should we store object state?

Serialization
Network
JVMJVM
SOAP Client Web Service

Syllabus
• Web Services: JAX-RPC-Concepts-Writing a
Java Web Service-Writing a Java Web Service
Client-Describing Web Services: WSDL-
Representing Data Types: XML Schema-
communicating Object Data: SOAP Related
Technologies-Software Installation-Storing
Java Objects as Files-Databases and Java
Servlets.

Web services - A Practical Approach

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