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Web Services

Web Services. Members Troy Tony Ellen Vincent. Web Services. What is it Why is it useful What have been solved Demo Alternative technologies Question. What is Web Service.

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Web Services

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  1. Web Services Members Troy Tony Ellen Vincent

  2. Web Services • What is it • Why is it useful • What have been solved • Demo • Alternative technologies • Question

  3. What is Web Service • An XML technology which allows an application to access a remote/local application’s services with very little code customization using ubiquitous and standard communication protocols. • Standard Package: • WSDL • UDDI • SOAP

  4. How Does It Work?

  5. How Does It Work?

  6. Why Web Service Useful • “you can exchange data between different applications and different platforms” (quoted from W3Schools.com) for the following reasons: • It is platform independent • It is language independent • It uses one of the most popular ways for data communication – XML • Enabling the reuse of software components • Delivers a loosely coupled architecture (e.g. SOA)

  7. What have been solved? • Technical point of view: Platforms / development languages conflict • Business point of view: enabling data exchange among different business partners while each one of them may use different types of servers/languages

  8. Web Service in the Real World • LiveJournal - Blog Management • Google Map / Geocoding • PayPal • Protein Data Bank

  9. Limitations of Web Service • Draw Back: • Once implemented, no control in response time of the service • XML (SOAP, WSDL) is easy for human (programmers) to read but have poor processing performance • Have no way to know how the clients will use the result from the web service. This limits the type of the data analysis/mining that can be performed.

  10. Demo • Python (install fpconst, SOAPpy) • Perl

  11. Web Services Demo Perl use SOAP::Transport::HTTP; use strict; SOAP::Transport::HTTP::CGI -> dispatch_to(‘Lottery') -> handle; package Lottery; sub lotteryNumbers { my ( $val, $seed) = @_; $seed ? srand $seed : srand; my @pools = ( 1 .. 49 ); my @numbers; while ( @numbers < 6 ) { my $n = int rand @pools; ( $pools[0], $pools[$n] ) = ( $pools[$n], $pools[0] ); push @numbers, shift @pools; } return (@numbers); } Python import SOAPpy import random server = SOAPpy.SOAPServer(('localhost', 8080)) server.registerFunction(numberGenerator) def numberGenerator(): list = range(1,50) lo_nums = [] i = 0 while i < 6: number = random.choice(list) if (number != -1): lo_nums = lo_nums + [number] list[number-1] = -1 i = i + 1 return lo_nums server.serve_forever() Link to Demo

  12. Alternative Technologies • MQ Series (from IBM) • Multi-platform and multi-language message queuing service • Asynchronus • One program queues messages • Another program processes messages • Managed by a Queue Manager; actions are event triggered • Two types of queue connections (called channels) • 1) Unidirectional and 2) Bidirectional • Applications can be loosely coupled with MQ Series but they must be contained within a cooperating system since connections are pre-established and static.

  13. Alternative Technologies

  14. Alternative Technologies • MQ Series (continued) • Strengths • Support for multiple platforms • Well tested and generally considered stable • Simplifies inter-application communications • Workflow management and load balancing • Queuing • Weaknesses • Message based rather than object based • Not stateful or persistent • Hard wired channels (communication links between apps) • Location is not transparent requiring more management

  15. Alternative Technologies • CORBA (Common Object Request Broker Architecture) • Platform and language independent • Object oriented component architecture • Stateful & persistent • Flexible features to decouple the client and object implementation • Performance is good enough for real-time applications • Support for transactions, security and events notification. • E.g. Linux Gnome – a network centric graphical user interface.

  16. Alternative Technologies

  17. Alternative Technologies • CORBA (continued) • Stengths • Platform independent (as long as there is vendor support) with multi-language support • Stateful and persistent objects • Widely deployed today • Integrated security services including its own naming service that minimizes the risk of spoofing, etc. • Service discovery • Weaknesses • Fairly complex to configure and implement • Not standardized for today’s network security issues. • Not organized for easy integration with web apps

  18. Alternative Technologies • DCOM (Distributed Components) • Object oriented • Objects are stateful, persistent, can pass data, event driven, … • Seamlessly connects local and remote COM objects into a running process (e.g. transparent use of remote objects) • Tightly interacts with ActiveX for web deployment and OLE. • Primarily Windows. • Microsoft support for MacOS and third party support for some UNIX (although UNIX COM not supported by developers thus very limited services) • Early issues regarding security, complexity, load balancing and others making it unsuitable for enterprise deployment. • COM+ and Microsoft Transaction Server (MTS) attempted to fix

  19. Alternative Technologies • COM Object Access

  20. Alternative Technologies • COM (continued) • Strengths • Multi-language support (kind of) • It doesn’t care where the object is sourced from • Statefulness, persistence, native data transfer and event capabilities (e.g. exceptions) • Relatively mature technology • Weaknesses • Platform dependent (platform must understand binary format) • Supports COM-aware languages only • Considered by many complex to develop and maintain

  21. Our Comments • What is cool… Troy: “Loosely coupled architecture” Vincent: “Free” Tony: “Code Reuse” Ellen: “Compatible”

  22. References http://www-128.ibm.com/developerworks/websphere/library/techarticles/0202_balani/balani.html http://www.sei.cmu.edu/str/descriptions/com.html http://www-128.ibm.com/developerworks/webservices/library/ws-exploring-corba/ http://www2002.org/CDROM/alternate/395/ http://www.cs.wustl.edu/~schmidt/corba-overview.html

  23. Questions?

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