Web Services in Perl

1
Web Services in Perl .NET

• John Zugel
• March 2004

2
But First
3
What Problem Are We Solving ?

• How can we distribute computing ?
• Granularity client/server vs function calls
• Naming and describing things
• Data encoding, transfer, decoding
• Finding and locating things
• Cross-platform, multi-language
• Transparency
• Security
• Fault, error, exception handling

4
The March of Technology

• Sockets
• Remote Procedure Calls (RPC)
• COM/DCOM, CORBA, Java/RMI
• HTTP
• XML
• SOAP
• Web Services

5
Sockets

• Peer-to-peer disguised as client-server
• Abstracted to IP address port
• Protocols datagram or stream
• Higher-level protocol left to user
• Byte-ordering
• Values vs references
• Locating peers
• Describing services

6
Remote Procedure Calls (RPC)

• Looks like a normal procedure call
• Hides network code in stub
• Simple types supported
• User-defined types possible
• By-reference simulated by copy/restore
• IDL makes coding easier
• Location, security, call semantics DIY

7
COM/DCOM, CORBA, Java/RMI

• Objects
• Heavyweight solutions
• Work best if you stay within the family
• Objects located by registry or repository
• Allows arbitrary data structures
• Exception handling
• Multiple-language support, kind of
• IDL and type information

8
HTTP

• Request-response protocol
• Header-body separation
• URLs / URIs as names and locators
• Textual content and MIME types
• CGI / ASP / PHP dynamic services
• Security and exception handling
• Not a distributed computing solution
• Ubiquitous !

9
XML

• Describes data IAW DTD or Schema
• Text-based
• Any/all data can be described
• Real data simple and complex types
• Fault, error, exception data
• Routing, naming/locating data
• DIY unless someone else already did it
• Ubiquitous !

10
Convergence !

• Server as container
• Fine-grained naming and locating
• Simple, extensible data encoding
• Simple, extensible metadata
• Transparent, cross-platform, multi-language
• Fine-grained services
• Security directory issues remain

11
What is a Web Service ?

• Software component
• Platform implementation-independent
• Invoked thru a declared API
• Described by a service description
• Published in a registry of services
• Can be composed with other services
• Discovered by a standard mechanism
• Ubiquitous !

12
Distributed Computing, Redux

• XML-RPC
• SOAP Simple Object Access Protocol
• WSDL Web Service Description Language
• UDDI Universal Description, Discovery and
  Integration (also DISCO and WSIL)
• But theres also ebXML and BPEL as alternative
  web services directions

13
SOAP

• Builds on RPC, HTTP, XML
• A message has an envelope, header (optional), and
  a body
• Used for both RPC and documents
• Security, authentications, transactions, and
  other requirements can be met by layering via
  actors and nodes
• mustUnderstand

14
SOAP Message Parts

• Envelope holds namespace URIs for versioning and
  encoding,
• Header provides OOB data (optional)
• Authentication security
• Routing, transactions, etc
• Error and handling instructions
• Body provides encoded data for final message
  recipient

15
A SOAP Message

• ltSOAP-ENVEnvelope xmlnsSOAP-ENVhttp//schemas.
  xmlsoap.org/soap/envelopegt
• ltSOAP-ENVHeadergt
• ltauthAuthorize xmlnsauthgt
• ltauthtypegtuserlt/authtypegt
• ltauthnamegtJoeUserlt/auth name gt
• lt/SOAP-ENVHeadergt
• ltSOAP-ENVBodygt
• ltcallgetQuote xmlnscallgt
• more stuff about the quote, perhaps
• lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

16
Simple Temperature Service

• Shamelessly stolen from xmethods.com
• See Xmethods Demo Services
• Implemented in Perl and .NET (C)
• Defines one operation getTemp ()
• Takes a string containing zipcode
• Returns a float containing temperature
• Monitored with Ethereal

17
Temperature Service WSDL

• lt?xml version"1.0" ?gt
• ltdefinitions name"TemperatureService"
• targetNamespace"http//www.xmethods.
  net/sd/TemperatureService.wsdl"
• xmlnstns"http//www.xmethods.net/sd
  /TemperatureService.wsdl"
• xmlnsxsd"http//www.w3.org/2001/XML
  Schema"
• xmlnssoap"http//schemas.xmlsoap.or
  g/wsdl/soap/"
• xmlns"http//schemas.xmlsoap.org/wsd
  l/"gt
• ltmessage name"getTempRequest"gt ltpart
  name"zipcode" type"xsdstring" /gt lt/messagegt
• ltmessage name"getTempResponse"gt ltpart
  name"return" type"xsdfloat" /gt lt/messagegt
• ltportType name"TemperaturePortType"gt
• ltoperation name"getTemp"gt
• ltinput message"tnsgetTempRequest" /gt
• ltoutput message"tnsgetTempResponse" /gt
• lt/operationgt
• lt/portTypegt

18
A Simple Web Service in Perl

• use SOAPLite
• zipcode shift
• print SOAPLite
• -gtservice("http//www.xmethods.net/sd/2001/T
  emperatureService.wsdl")
• -gtgetTemp(zipcode)
• Invoked by perl GetTemp.pl 95133
• The SOAPLite toolkit does all the heavy lifting

19
A Simple Web Service in .NET

• // TemperatureService is the proxy to the web
  service.
• // First, instantiate the proxy
• TemperatureService tempSvc new
  TemperatureService( )
• // Next, call the service via the proxy
• Single result tempSvc.getTemp(
  zipCodeEntry.Text )
• wsdl.exe generates the proxy class
• Visual Studio .NET does all the work

20
What was the point of all this ?

• Web services look like objects
• Web services are easy
• If you dont have to deal with the XML
• If you dont have to deal with connectivity
• If you dont have to deal with locating the
  service you need

21
Programming Web Serviceswith Perl

• Randy Ray Pavel Kulchenko
• OReilly, 2003
• 437 pages
• 39.95, discounted to 27.97 on Amazon
• 5 stars, 5 reviews

22
Programming Microsoft .NET

• Jeff Prosise
• Microsoft Press, 2002
• 773 pages
• 59.99, discounted to 41.99 on Amazon
• 4.5 stars, 19 reviews

23
Web Resources

• World Wide Web Consortium (w3.org)
• SOAPLite Perl toolkit (soaplite.com)
• Cygwin Unix-on-Win32 (cygwin.com)
• CPAN for Perl (cpan.org)
• ActiveState Perl (activestate.com)
• Microsoft .NET Framework SDK (msdn.microsoft.com)
• Publicly available web services (xmethods.net)

24
The Last Word