Web Services Introduction

• Web Services are required to communicate between two different applications.
• An application have access rights to it’s own database only, so when another external application needs data from it’s database, it never provides access to it's own database (because of some security & other issues) and hence data access is provided through Web Services.
• For example we can withdraw money from several ATM booth using a particular bank’s ATM Card.
• Web Services don’t provide any API they just provide some Specifications (set of rules) to communicate between applications
• Six components Web Services provides to communicate between them:
• WSDL - Web Services Descriptor Language is nothing but an XML file consists of implementation details (i.e. class, method, parameter info etc) of server side class that client may wish to invoke.
• UDDL - Universal Description Discovery and Integration. It's a registry or repository where client can look for available Web Services.
• SKELETON - These are basically servlets, configured in the web.xml file of the server application with some url pattern.
• STUB
• SOAP Protocol
• HTTP Protocol