web service notes

why do we need web service?

1     1)  we need web service to integrate different applications. It can also be done through the web application with other available middleware with integration/middleware technologies but with a big pain and higher price.

2      2)  Web service is a new kind of middleware based on XML and the Web. They are platform and language independent. Web service has no relation to web browser and HTML.web application is dependent on browser and different issues like firewall is associated with it which is not with web service.

3       3) any web application programmed for firefox will not operate properly on internet explorer but this is not the issue with web service as web services are plateform independent.

4      4)  if we go with any other middleware like CORBA and EJB, they are highly coupled means client and server has the knowledge of each other while in web service client need not require to know about the server and so it enhances loose coupling.

5      5)  there is no any standard defined for the application interaction. standard is there in webservice.

What is advantage of using soap?

·         *Platform independent.

·          *Language independent.

·          *XML for communication.

·          *SOAP is also a simple way to accomplish communications.

·          *Uses standard internet HTTP protocol.

·          *no firewall problems.

·          *very simple compared to RMI, CORBA, and DCOM because it does not deal with certain ancillary but important aspects of remote object systems.

·          *protocol for exchanging information in a decentralized and distributed environment.

·          *Vendor neutral.

What is SOAP?
SOAP is a simple XML-based protocol to let applications exchange information over HTTP. SOAP=Xml+HTTP
 pats of soap are:
  envelope: indicates the start and the end of the message
  header : digital signature for password-protected services;
  body : contains mandatory information intended for the ultimate receiver of the message.
  soap fault: contains the error occured during processing. it has fault code and fault string


what are disadvantage of soap? 
1)SOAP clients do not hold any stateful references to remote objects.
 2)very bulky

what are their requirements before making a web service?
1. SOAP (Simple object access protocol)
 2. UDDI (Universal Description, Discovery and Integration)
 3. WSDL (Web Services Description Language)

what is xml namespace?
 provide a method to avoid element name conflicts.