CORBA AND SOAP Unmesh Kulkarni i2 Group Ashish V. Tendulkar Directory Database integration group ( Persistent Systems Pvt. Ltd. Pune (

OUTLINE Introduction to middleware CORBA Concepts Problem Domain SOAP Synergies Conclusion

What is Middleware?  Glue for Components  Sits Between OS and Applications  Distributed Object Services  CORBA, COM, DCE, Java/RMI …  XML?

CORBA - Objectives  OS Independence  Language Independence  Remote Methods  Static/Dynamic Invocations  Distributed Services

Interoperability Standardization of –  Binary Formats : in-memory  API’s : Programming Support  IDL, Type Libraries, File Formats  Data Representation – CDR/NDR  Transfer Protocol

CORBA provides.. The PRO’s :  IDL  Stub-skeleton generators  Services API’s  CDR  IIOP And The CON’s  Complexity  Vendor dependency  Costly - large volumes  Behavior marshalling  Internet / Firewalls  COM-CORBA Inter- operability

The problem.. Client App. Proxy Server Server Application Server Firewall

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

Why XML?  Simple text markup language  Platform, language and vendor agnostic  Easily extensible  Capable of solving interoperability problem

Why HTTP?  Ubiquitous  Supported by every web browser and server  Effective technology for transferring text, graphics and other information

XML + HTTP = SOAP  HTTP is used for transport  XML as encoding scheme  Endpoint HTTP based URL for the target  Object mapping: implementation specific

SOAP call anatomy

SOAP Component HTTP Headers SOAP method name SOAP Envelope SOAP Header SOAP Body Call element Object Endpoint ID Method/Interface ID Extension Headers Parameter Data

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

Example Message POST /string_server/Object17 HTTP/1.1 Host: Content-Type: text/xml Content-Length: 152 SOAPMethodName: urn:strings-com:IString#reverse Hello, World

Example Response 200 OK Content-Type: text/xml Content-Length: 162 dlroW,olleH

 IOR : Object Reference  Interface Name /Method Name  Method Invocation with Parameters  POST/ObjectUR I HTTP/1.1  SOAP:MethodNa me  SOAP:Envelope  SOAP:Header  SOAP:Body  SOAP:CallEleme nt CORBA vs SOAP

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

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)

XML With CORBA  XML – Structure  CORBA – Infrastructure  XMI – Metadata Interchange  XML Interfaces – Components accepting/emitting XML documents

XML With CORBA…. Examples :  XMI – Exchange of UML models between Design tools and repositories  Persistent storage of components in IDE’s:  JavaBean Persistence  Resilience to versioning of libraries/VM’s  Defaults/Redundancy elimination

Synergy

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