Copyright © 2013 Curt Hill SOAP Protocol for exchanging data and Enabling Web Services

Copyright © 2013 Curt Hill

SOAPProtocol for exchanging data

and Enabling Web Services

SOAP

• Simple Object Access Protocol• Designed for applications to

communicate with one another• Uses Internet (TCP/IP and HTTP)• Transferred data is in XML• Platform and language

independent• Backed by W3C


Previous Attempts• Most of the previous attempts had

problems• Remote Procedure Calls raise

security issues– DCOM or CORBA are two RPC

standards– They are a lot more work

• XML cannot contain programs or viruses, so no security issues

• Will have no problems with a firewall or proxy server


Messages

• SOAP messages are just XML documents

• Such a message contains– Envelope element– Header element– Body element– Fault element


Envelope element

• Defines this XML document as a SOAP message

• This is the only element in the XML document

• Header and Body are within Envelope– Fault is within Body


Header element

• Optional element • Gives information not in the body• Instructions for different roles may

be specified here– For example the ultimate receiver

may get different instructions than those nodes who only pass on the XML


Body element

• The client puts the request here to send to the web service

• The service puts the response here to send back to the client

• The content of either is dependent on the web service


Fault element

• Contains error information generated by the web service to be sent back to the client

• This should be checked to determine the validity or importance of the body


WSDL

• Web Services Description Language

• Gives a description of the services offered by a particular web service provider

• WSDL uses XML to define the available services


WSDL and SOAP

• An application can obtain the WSDL description of the services provided

• It may then generate a SOAP request for use of these services

• The provider responds with a SOAP response


Pros and Cons

• SOAP uses XML which can be transmitted through HTTP and other protocols

• Platform independence• Disadvantage: the XML is self

describing, this makes it bulky– That is less of an issue than before


UDDI• Universal Description, Discovery and

Integration• One form of a directory service to

register available web services and search for web services

• Uses WSDL to describe web services and SOAP to transmit them

• SOAP does not need UDDI to function– Any means of finding providers will suffice


Documents

Copyright © 2013 Curt Hill SOAP Protocol for exchanging data and Enabling Web Services