Core mechanisms for Web Services extensions
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The document discusses core mechanisms for developing Web Services extensions. It proposes mechanisms like policy, configuration, context management, message flow interception, and operation implementation interception. These mechanisms were implemented in a proof-of-concept to develop extensions for security and distributed transactions. Web Services extensions can simplify custom library development and broaden the developer community. Future work includes developing an enterprise application framework and platform-independent extensions.
Core mechanisms for Web Services extensions
- 1. 2007 Next Generation Web Services Practices Core mechanisms for Web Services extensions Miguel Pardal miguel.pardal@dei.ist.utl.pt Lisbon, Seoul, October 30th, 2007 Portugal
- 2. Outline • Service-oriented Enterprise Applications • Web Service Extensions – Core mechanisms • Conclusions 2007-10-30 Core mechanisms for Web Services extensions 2
- 3. Outline • Service-oriented Enterprise Applications • Web Service Extensions – Core mechanisms • Conclusions 2007-10-30 Core mechanisms for Web Services extensions 3
- 4. “The whole world is made of change” ~ Luís Vaz de Camões 16th Century Portuguese Poet Cobol Fortran C DCE Java CORBA Dot Net DCOM Web Services 2007-10-30 Core mechanisms for Web Services extensions 4
- 5. Service-oriented approach to Enterprise Applications • Customers’ needs change – Enterprises must adapt – And so do their applications • Services – Focus on flexibility, reuse and interoperability – Web Services (WS) technology – Service-Oriented Architecture (SOA) 2007-10-30 Core mechanisms for Web Services extensions 5
- 6. Web Services in action #1 Publish Client Service #2 Discover Data XML Schema WS #3 Generate stubs Functions WSDL #4 Configure Policy WS-Policy WS libraries #5 Invoke #6 Execute 2007-10-30 Core mechanisms for Web Services extensions 6
- 7. Web Services libraries #4 Configure Policy WS-Policy WS libraries • WS-Policy specifies additional requirements – Like security, distributed transactions, reliable messaging, etc. – But libraries are necessary to actually implement the requirements 2007-10-30 Core mechanisms for Web Services extensions 7
- 8. Requirements • Functional – What the service does • Input, output, faults • Non-functional – What properties hold when the service executes – Depend on circumstances and must be balanced • E.g. Security – Low value messages can use a weaker but faster cipher algorithm; high value messages use stronger security – Intranet requests use local security credentials; Internet requests use cross-domain credentials 2007-10-30 Core mechanisms for Web Services extensions 8
- 9. Outline • Service-oriented Enterprise Applications • Web Service Extensions – Core mechanisms • Conclusions 2007-10-30 Core mechanisms for Web Services extensions 9
- 10. WS standards for every requirement “Are we there yet?” Short answer: No, but we’re moving forward Long answer: Visit WS-Map ☺ (or another overview site…) http://web.ist.utl.pt/miguel.pardal/ws-map 2007-10-30 Core mechanisms for Web Services extensions 10
- 11. Why go beyond the standards? • “One size does not fit all” • Vendor WS implementations – From Microsoft, IBM, Sun, Oracle, … – Good library implementations of complex WS standards – Solve 90% of the problem but are difficult to customize to specific needs • WS Extensions – Simpler library development – Appeal to a much broader developer community – Handle the remaining 10%... 2007-10-30 Core mechanisms for Web Services extensions 11
- 12. Analogy: Mozilla Firefox extensions • Firefox implements 90% of requirements – Extensions add value to users, meeting specific needs and improving the browsing experience 2007-10-30 Core mechanisms for Web Services extensions 12
- 13. Example extension: Security report • Some applications prefer not to know about security, they just want it – But others need to know, for instance, to store audit information in a database • Security report extension – A report is produced during WS-Security processing • All actions and all parameters described • In a simple, easy-to-use object model – Leverage WS-Security standard implementation – Enables context sharing through meaningful abstractions, delegating security decisions in a simple and effective way 2007-10-30 Core mechanisms for Web Services extensions 13
- 14. Problem statement • What are the core mechanisms required for developing Web Services extensions ? – Like “security report” 2007-10-30 Core mechanisms for Web Services extensions 14
- 15. Proposed core mechanisms • Policy • Configuration • Contexts management • Message flow interception • Operation implementation interception Packages and dependencies 2007-10-30 Core mechanisms for Web Services extensions 15
- 16. Policy • Requirements declaration – e.g. Declare that a WS can be invoked with transport security or with message security • Policy negotiation between client and server 2007-10-30 Core mechanisms for Web Services extensions 16
- 17. Configuration • Parameters – Which extensions to engage? – What are the parameter values? • e.g. Which digital certificate to use? 2007-10-30 Core mechanisms for Web Services extensions 17
- 18. Contexts management • Scoped state variables – Application – Session – Operation – Thread • Enable data sharing between extensions and service implementation 2007-10-30 Core mechanisms for Web Services extensions 18
- 19. Message flow interception • Message handling at service endpoint – Incoming or outgoing – Read/write header and body of SOAP messages • e.g. Do digital signature of body and place it in header 2007-10-30 Core mechanisms for Web Services extensions 19
- 20. Operation implementation interception • Execute additional code before or after the service implementation – e.g. Implement authorization and access logging • Object factories can return different implementations according to the desired behavior 2007-10-30 Core mechanisms for Web Services extensions 20
- 21. Proof-of-concept • All mechanisms implemented on Java Web Services – Apache Commons Policy 1.0 • Policy – JAX-WS Handlers • Message interception – Custom coding • Configuration, Contexts and Operation Execution • Field-tested on a prototype and several course projects: – Security and distributed transactions extensions – Multiple development teams – Significant improvements in ease of development and learning 2007-10-30 Core mechanisms for Web Services extensions 21
- 22. Outline • Service-oriented Enterprise Applications • Web Service Extensions – Core mechanisms • Conclusions 2007-10-30 Core mechanisms for Web Services extensions 22
- 23. Conclusions • Web Services development – Functional requirements are satisfied with components – Non-functional requirements are satisfied with aspects that can differ according to invocation circumstances • Web Services extensions – Simplify custom library development – Broaden developer community • Future work: – Enterprise application framework • Local and remote services • Integrated extensions engine – Platform-independent extensions: Java and Dot Net 2007-10-30 Core mechanisms for Web Services extensions 23
- 24. Looking ahead… With extensions, more developers can try new ideas. This encourages competition and best-of-breed selections, that can further advance the state-of-the-art of Web Services technology Obrigado Thank you Questions & Answers miguel.pardal@dei.ist.utl.pt 2007-10-30 Core mechanisms for Web Services extensions 24