Transcript Web Services (Nuts and Bolts) ITEC 625 Web Development Fall 2006

Web Services
(Nuts and Bolts)
ITEC 625 Web Development
Fall 2006
Reference:
Building Web Services with Java (Making sense of XML,
SOAP, WSDL, and UDDI), “Web Services Basics Part I”
(Chapters 1-6),Graham et al., Developers Library, 2004
Service-Oriented Architectures
(SOAs)
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Main roles
• Service provider
• Service description
• Service requestor
• Service registry
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Operations
• Publish, find, bind
Why the fuss?
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SOA augments and grows your applications portfolio to a
portfolio of components (services and apps composed of
services)
Organizations better able to construct software to
integrate business processes and respond rapidly to
changes in business environment.
Implicit, seamless software integration
Approach makes it easier to focus on business processes
and tasks as services; less need to focus on underlying
technical details of a service.
Easy selection of service interface design, most
appropriate and existing IT investments for ease of
building SOA, and best business processes.
Justifying Web Services
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Application integration is faster, cheaper
Many options for integration using many types
of devices (PDAs, cell phones, desktops, etc)
Time to market is reduced
Use of standards provides benefits (choice of
tools, more vendor options)
Relatively low cost of entry
Interface-based development reduces time to
integrate applications
Web Services vs. SOA
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Associated but distinct.
SOA
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An architectural concept, approach to building
systems that focuses on loosely coupled set of
component services that can be dynamically
composed.
Web Services
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One approach to building an SOA, providing a
standard for a particular set of XML-based
technologies that can be used to build SOA systems.
XML
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Document-centric vs Data-centric
Instances (prolog, elements, attributes)
Namespaces
Schemas
• Well-formed, iaw rules of XML syntax
• Valid, iaw DTD or Schema
• Parsers can be validating/non-validating
• If Valid, then well-formed
XML Processing
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Pull parsing: application asks parser to give it the next
piece of info about the doc
Push parsing, event-based parsing: parser sends info to
application about XML doc pieces encountered during the
parse, sent in order, as they appear. Simple API for XML
(SAX v. 2.0)
One-step parsing, DOM parsing. Parser reads whole
document, generates a data structure (tree), deeply
nested; DOM is language and platform independent.
Don’t map well to native data structures, thus JDOM
(Java DOM) for simplifying manipulation of doc trees in
Java
Hybrid parsing, combinations
Issues: Memory efficiency, computational efficiency, ease
of programming
Also JAXP, Java API for XML Processing, version 1.2
XML Resources
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DOM Level 1, 2
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http://www.w3.org/TR/REC-DOM-Level-1 or 2
JAXB
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http://java.sun.com/xml/downloads/jaxb.html
JAXP
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http://java.sun.com/xml/xml_jaxp.html
JDOM
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http://www.jdom.org/docs/apidocs
JSP1.2
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http://java.sun.com/products/jsp
SAX
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http://www.saxproject.org/
XML, XML Namespaces, XML schema
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http://www.w3.org/TR/REC-xml
http://www.w3.org/TR/REC-xml-names
http://www.w3.org/TR/xmlschema-0/ or 1 or 2
SOAP Protocol
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Version 1.2
Two parts for spec
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Part 1, the Messaging framework, central foundation
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Part 2, the Adjuncts
• Processing model
• Extensibility model
• Message structure
• Optional
• But give enough to developers (core of Part 1 is not
enough)
SOAP Resources
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XML Protocol Working Group
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http://www.w3.org/2000/xp/Group
SOAP 1.2 and Primer
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http://www.w3.org/TR/SOAP
http://www.w3.org/TR/2003/REC-soap12-part0-20030624/
SOAP with attachments
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http://www.w3.org/TR/SOAP-attachments
MTOM
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http://www.w3.org/TR/soap12-mtom/
XOP
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http://www.w3.org/TR/xop10/
Describing Web Services
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WSDL is an IDL (Interface Description
Language)
A WSDL description describes:
• What a service does, operations (methods),
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data needed (arguments and returns)
How a service is accessed, data formats and
protocols, etc .
Where a service is located, URL, etc.
Major elements of WSDL
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portType
message
types
binding
port
service
WSDL Resources
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WSDL 1.1 and 2.0
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http://www.w3.org/TR/wsdl
http://www.w3.org/2002/ws/desc/wsdl20
WS-Policy and PolicyAttachment
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http://www-106.ibm.com/developerworks/library/wspolfram/
http://www-106.ibm.com/developerworks/library/wspolatt/
Implementing Web Services
with Apache Axis
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One of best Java-based Web services
engines
One of most extensible, can be tuned to
support new versions of SOAP
Can run on top of simple servlet engine
or a full-blown J2EE application server
http://ws.apache.org/axis
Axis Resources
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Apache Axis
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http://ws.apache.org/axis
Log4j
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http://logging.apache.org/log4j/docs/
Jakarta Discovery library and commons
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http://jakarta.apache.org/commons/discovery/
http://jakarta.apache.org/commons/net/
JUnit
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http://junit.org
SOAP builders
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http://groups.yahoo.com/group/soapbuilders
Discovering Web Services
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Request copy of service description directly
from provider
Centralized service registry (UDDI)
Other publication and service discovery
mechanisms
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At service provider’s point of offering
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Public repository of WSDL documents
• Using WS-Inspection specification (see resources)
• http://www.salcentral.com
• http://www.xmethods.com
UDDI Datatypes
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businessEntity
businessService
bindingTemplate
tModel
publisherAssertion
Using a UDDI Registry
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A UDDI registry is itself an example of a Web Service
Entries in the registry can be published and queried using
a SOAP-based interface
SOAP-based interface is used for all publish and query
operations
Publishing usually requires registration and authentication
token for creating, updating, deleting entries in the
registry
For publishing…Each datatype uses Save API and Delete
API
For inquiry… Each datatype uses Find API and Get API
WSDL Service Interface
Definitions for UDDI Registry
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Inquiry API v2.0
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http://uddi.org/wsdl/inquire_v2.wsdl
Publication API v2.0
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http://uddi.org/wsdl/publish_v2.wsdl
API v3.0 portTypes
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http://uddi.org/wsdl/uddi_api_v3_portType.wsdl
API v3.0 Bindings
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http://uddi.org/wsdl/uddi_api_v3_binding.wsdl
UDDI Resources
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UDDI specs
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http://www.oasis-open.org/committees/uddispec/doc/tcspecs.htm
UDDI best practices
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http://www.oasis-open.org/committees/uddispec/doc/bps.htm
UDDI technical notes
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http://www.oasis-open.org/committees/uddispec/doc/tns.htm
WS-Inspection
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http://www106.ibm.com/developerworks/webservices/library/wswsilspec.html