SOAP web service tutorial

Simple Object Access Protocol (SOAP) is a standard protocol specification for message exchange based on XML. Communication between the web service and client happens using XML messages.
A simple web service architecture have two components

• Client
• Service provider

So as in above diagram,how client will communicate to service provider.So in order to communicate client must know some information for e.g.

• Location of webservices server
• Functions available,signature and return types of function.
• Communication protocol
• Input output formats

Service provider will create a standard XML file which will have all above information.So If this file is given to client then client will be able to access web service. This XML file is called WSDL.

What is WSDL?

WSDL stands for Web Service Description Language. It is an XML file that describes
the technical details of how to implement a web service, more specifically the URI,
port, method names, arguments, and data types. Since WSDL is XML, it is both
human-readable and machine-consumable, which aids in the ability to call and bind to
services dynamically.using this WSDL file we can understand things like,

•     Port / Endpoint – URL of the web service
•     Input message format
•     Output message format
•     Security protocol that needs to be followed
•     Which protocol the web service uses

Ways to access web service:

There are two ways to access web service.

• If Service provider knows client:If service provider knows its client then it will provide its wsdl to client and client will be able to access web service.

• Service provider register its WSDL to UDDI and client can access it from UDDI:UDDI stands for Universal Description, Discovery and Integration.It is a directory service. Web services can register with a UDDI and make themselves available through it for discovery.So following steps are involved.
  1. Service provider registers with UDDI.
  2. Client searches for service in UDDI.
  3. UDDI returns all service providers offering that service.
  4. Client chooses service provider
  5. UDDI returns WSDL of chosen service provider.
  6. Using WSDL of service provider,client accesses web service.