CORBA AND SOAP

1
CORBA AND SOAP

• Unmesh Kulkarni
• i2 Group
• Ashish V. Tendulkar
• Directory Database integration group
• (www.eusersolutions.com)

• Persistent Systems Pvt. Ltd. Pune
• (www.pspl.co.in)

2
OUTLINE

• Introduction to middleware
• CORBA Concepts
• Problem Domain
• SOAP
• Synergies
• Conclusion

3
What is Middleware?

• Glue for Components
• Sits Between OS and Applications
• Distributed Object Services
• CORBA, COM, DCE, Java/RMI
• XML?

4
CORBA - Objectives

• OS Independence
• Language Independence
• Remote Methods
• Static/Dynamic Invocations
• Distributed Services

5
Interoperability

• Standardization of
• Binary Formats in-memory
• APIs Programming Support
• IDL, Type Libraries, File Formats
• Data Representation CDR/NDR
• Transfer Protocol

6
CORBA provides..

• And The CONs
• Complexity
• Vendor dependency
• Costly - large volumes
• Behavior marshalling
• Internet / Firewalls
• COM-CORBA Inter-operability

• The PROs
• IDL
• Stub-skeleton generators
• Services APIs
• CDR
• IIOP

7
The problem..
Proxy Server
Server
Client App.
Application Server
Firewall
8
Implications

• Industry not shifted completely to either one
• Vendor specific
• Lack of interoperability
• Require high-tech runtime environment

9
Why XML?

• Simple text markup language
• Platform, language and vendor agnostic
• Easily extensible
• Capable of solving interoperability problem

10
Why HTTP?

• Ubiquitous
• Supported by every web browser and server
• Effective technology for transferring text,
  graphics and other information

11
XML HTTP SOAP

• HTTP is used for transport
• XML as encoding scheme
• Endpoint HTTP based URL for the target
• Object mapping implementation specific

12
SOAP call anatomy
13
SOAP Component
Object Endpoint ID
Method/Interface ID
Extension Headers
Parameter Data
Call element
14
Uses of SOAP

• SOAP greatly simplifies data exchange in B2B
  application over extranet
• Enables web site to integrate services from other
  sites
• Remote scripting more prevalent with SOAP
• Non-browser client could seamlessly access a
  service across web

15
Example Message

• POST /string_server/Object17 HTTP/1.1
• Host 209.110.197.2
• Content-Type text/xml
• Content-Length 152
• SOAPMethodName urnstrings-comIStringreverse
• ltEnvelopegt
• ltBodygt
• ltmreverse xmlnsm'urnstrings-comISt
  ring'gt lttheStringgtHello, Worldlt/theStringgt
  lt/mreversegt
• lt/Bodygt
• lt/Envelopegt

16
Example Response

• 200 OK
• Content-Type text/xml
• Content-Length 162
• ltEnvelopegt
• ltBodygt
• ltmreverseResponse xmlnsm'urnstrings-
  comIString'gt
• ltresultgtdlroW ,olleHlt/resultgt
• lt/mreverseResponsegt
• lt/Bodygt
• lt/Envelopegt

17
CORBA vs SOAP

• IOR Object Reference
• Interface Name /Method Name
• Method Invocation with Parameters

• POST/ObjectURI HTTP/1.1
• SOAPMethodName
• SOAPEnvelope
• SOAPHeader
• SOAPBody
• SOAPCallElement

18
Advantages

• Simplest Data Representation
• Hardware/Language Neutral
• No Vendor Dependencies
• Simple and Human-readable
• Typing Flexibility
• Firewall Issues

19
Then Why Not XML?

• Distribution Support
• Resource location, control and management
• Services Transactions, Events, Security etc.
• Error Handling
• Non-text data
• Quality of Service Reliability
• Efficiency (Redundancy Elimination)

20
XML With CORBA

• XML Structure
• CORBA Infrastructure
• XMI Metadata Interchange
• XML Interfaces Components accepting/emitting
  XML documents

21
XML With CORBA.

• Examples
• XMI Exchange of UML models between Design tools
  and repositories
• Persistent storage of components in IDEs
• JavaBean Persistence
• Resilience to versioning of libraries/VMs
• Defaults/Redundancy elimination

22
Synergy
23
Conclusion

• SOAP is platform independent, language neutral
  protocol
• SOAP does not replace COM and CORBA
• SOAP works in place of DCOM and IIOP
• SOAP does not pose huge security risks
• Supports interoperation between different vendor
  specific implementations