Learn how Web Services are used to build interoperable distributed services across different platform.

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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 platform
Clients on other platforms can not utilize the services
Changes in server-side environment affect all the clients
•Client must have server side API for interaction
Client 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 proprietary
Client 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

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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

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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

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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”
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Who will benefit?
Developers and Programmers, who wish to build interoperable distributed
services across different platform.
View Complete Details

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