Web Services, SOAP, and
WSDL
CSCI 4300
Web Services for B2B
communication
Technology involved for remote
procedure call
• Web Service
Description Language
is the API
• SOAP is the message
envelope
• HTTP is the transport
layer
Remote Method Invocation
• Low-level
• Requires all parts
written in Java
• CORBA is one
attempt to get
around this issue
JAX RPC layered over RMI
Simple SOAP message
SOAP headers and body
Headers:
• Security credentials
• Transaction IDS
• Routing instructions
• Payment tokens
• Etc. etc.
Body:
• Actual message
content
Application-specific header
example
A security header
Processing SOAP messages
• In particular, JAX-RPC implements remote
procedure calls by exchanging SOAP messages
Modular processing
Message passing: multiple actors
Who processes the headers?
• A node which has identified itself with this
processing role will process this header.
SOAP use case
Sequential processing
• Processing nodes can add and remove headers
• The Inventory node can add an authentication
header and force the next node to process it
Web Services Description
Language
“portType”: a service access point
Operation types
WSDL – SOAP binding
• The binding determines the format of the SOAP
message that will transport a service
UDDI: the Yellow Pages
Acknowledgements
• Auto parts example:
http://www.info.gov.hk/digital21/eng/knowledge/webservice_appexa
mple.html
• http://today.java.net/today/2003/11/05/ch4SOAP.pdf
• http://java.sun.com/developer/technicalArticles/xml/webservices/
• http://www.w3schools.com/wsdl/wsdl_documents.asp