SpringPeople Introduction to JAVA Web Services

7/28/2019 SpringPeople Introduction to JAVA Web Services

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Introduction to JAVA Web

Services


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What are Web Services?

Web Services are used to build interoperable distributed services across

different platform.

The client and server can be developed on different platforms and in

different languages, yet they can exchange requests and responses.

For example, a Java client can consume a .NET based service and vice-versa

Legacy or new systems can be integrated rather easily by exposing them as

web services.

A better ROI from every system can be achieved.


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Typical Distributed Architecture


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Distributed Architecture Examples

Java Platform

RMI (Remote Method Invocation), EJB (Enterprise Java

Beans), CORBA, now not so famous

@Remote interface as the interface @SessionBean as implementation

JNDI Directory as the registry

JBoss as the service container & publisher

InitialContext.lookup() for fetching proxy on the client side

COM/DCOM on Microsoft platform


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Major Shortcomings of

Distributed System

Both client and server must be on the same platformClients on other platforms can not utilize the services

Changes in server-side environment affect all the clients

Client must have server side API for interactionClient can not be developed unless the API is distributed

Often the API may be priced, poorly documented and etc.,

The protocol between client and server is also platform specific

and often proprietaryClient that wants to connect to several remote objects have to implement

all the specified protocols


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Web Service Architecture

Solution


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Web Services Standards

Web Services are build on three foundation standards

Web Service Definition Language (WSDL): An XML based IDL to

describe the service definitions in a language agnostic way

Service Oriented Architecture Protocol (SOAP): An XML based PDU for

communication between the clients and services Universal Description Discovery and Integration (UDDI): An XML based

registry for service publication and discovery

Bodies like OASIS proposed and publicized other standards as well

Standards like WS-Address, WS-Security, WS-Authentication and etc.,

are built on top of foundation standards



Web Service Definition Language

(WSDL)What is WSDL?

Its an IDL for describing a web service interface.

The service is meant for the clients of any platform.

Its XML based.

Who develops them?

WSDL is hand-written in Contract-First Approach

WSDL is generated in Contract-Last Approach



What WSDL consists of?

An abstract section

Types: Describes the XML types & elements that are used in the messages

to/from the web services.

Messages: Describes the input, output and fault messages that comes into

and goes out of web service operations. PortType: Names the web service and describes the operations offered by

the web service

A concrete section

Bindings: Describes the transport protocol like HTTP to carry the SOAP

envelope for communicating with web service.

Service: Describes the endpoint where the service is really available for

consumption



SOAP/XML

What is SOAP?

It stands for Service Oriented Architecture Protocol in the

SOA/Web Services combination.

It originally stood for Simple Object Access Protocol when web

services were merely meant for lightweight RPC calls.

What is its job?

It carries the payload for request/response between the client

and the server.

Obviously its an XML document (JSON is also supported)


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Who writes and consumes

SOAP/XML? Web Service clients/servers dynamically prepares and

consumes the SOAP envelopes


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Who carries SOAP and what it

consist of? HTTP or protocol (as specified in WSDL) carries it

It consists of optional Header and mandatory Body


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Web Services v/s SOA

Web Services is one of the technologies to implement Service Oriented

Architectures (SOA)

However, Web Services predates SOA.

Primary intention of web services was to make RPC calls, later it

became a technology of choice for SOA implementation

Clients can be developed as an orchestration of services from various

endpoints that confirms to SOA

Business processes can be delivered in accordance with Software As

A Service (SAAS) paradigm.

Services needs not be installed at client site, they are just consumed.


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Become a Web Services Expert In

3 Days Flat

Attend the 3-Days Web Services Workshop

View Complete Details
http://www.springpeople.com/courses/regular/web-services-training-course.phphttp://www.springpeople.com/courses/regular/web-services-training-course.php


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Who will benefit?

Developers and Programmers, who wish to build interoperable distributed

services across different platform.

View Complete Details
http://www.springpeople.com/courses/regular/web-services-training-course.phphttp://www.springpeople.com/courses/regular/web-services-training-course.php


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Q & A

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SpringPeople Introduction to JAVA Web Services