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Web Services Members Troy Tony Ellen Vincent
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• 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:1. WSDL
2. UDDI
3. SOAP
How Does It Work?
How Does It Work?
Why Web Service Useful
• “you can exchange data between different applications and different platforms” (quoted from W3Schools.com) for the following reasons:
1. It is platform independent
2. It is language independent
3. It uses one of the most popular ways for data communication – XML
4. Enabling the reuse of software components
5. Delivers a loosely coupled architecture (e.g. SOA)
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
Web Service in the Real World
• LiveJournal - Blog Management
• Google Map / Geocoding
• PayPal
• Protein Data Bank
Limitations of Web Service
• Draw Back:1. Once implemented, no control in response time of the
service
2. XML (SOAP, WSDL) is easy for human (programmers) to read but have poor processing performance
3. 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.
Demo
• Python (install fpconst, SOAPpy)
• Perl
Web Services Demo
Python
import SOAPpyimport 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
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);}
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.
Alternative Technologies
Received Message
Received Message
Retrieved Message
Queued Message
Queued Message
TransmittingMessage
MQ Series
TransmittingMessage
Queue 1 Queue 2
ConsumingApplication
ServingApplication
New Message
Alternate bi-directionalcommunicationQueue Manager (Triggers)
Queue Manager (Triggers)
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
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.
Alternative Technologies
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
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
Alternative Technologies
• COM Object Access
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
Our Comments
• What is cool…
Troy: “Loosely coupled architecture”
Vincent: “Free”
Tony: “Code Reuse”
Ellen: “Compatible”
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
Questions?
