Martin: Created page with "= Web Services = == References == Jboss users guide to web services http://www.jboss.org/jbossws/docs/jaxws_userguide-2.0/index.html == Definitions == URI - uniform resource..."

2021-09-14T21:21:44Z

Created page with "= Web Services = == References == Jboss users guide to web services http://www.jboss.org/jbossws/docs/jaxws_userguide-2.0/index.html == Definitions == URI - uniform resource..."

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= Web Services =
== References ==
Jboss users guide to web services
http://www.jboss.org/jbossws/docs/jaxws_userguide-2.0/index.html

== Definitions ==
URI - uniform resource identifier both below are URIs
URN - uniform resource name e.g. urn:luminoussheep
URL - uniform resource locater - resolvable address e.g. http://luminousheep.net

== Components ==
# service provider - WSDL
# consumer
# service broker - UDDI

* WSDL describes service
** what operations
** where to find it, how to communicate - protocol (portType)
** format,encoding of messages (binding)
* UDDI advertises service
** tModel (technical model) - describes abstract resource - points to WSDL
** Categorises by service type
* SOAP communication mechanism

Separating the what from the how and where allows different service providers to be used with ease

UDDI
# supplier specific information such as company, address
# categorisation information
# technical service implementation information - binding template

== uses ==
* connects disparate systems - different platforms - OS and language
** use in heterogeneous environments supports all languages, all platforms
** useful where no control over clients
* useful for supporting different display interfaces - web/mobile/desktop
* dynamic conditions - easy to update
* aggregating information - portals, customer care, collaboration
** multi channel - rich clients - IVR (interactive voice response)
* reduce redundancy - can be used to centralise services

* no component model - no framework
* overhead - performance - can introduce scaling issues
* not a replacement in itself for ESB (extract, aggregate, transform, route)
* better off using native communication for local apps

Reference http://www.oracle.com/technology/sample_code/tech/java/j2ee/jintdemo/tutorials/webservices.html

== SOAP ==
* Envelope wrapping a Header and Body
* Header - system level information such as security, transaction context, message correlation, session id - optional
* Body - payload - required

Can be routed though intermediaries that operate transparently performing logging/authentication/decryption

=== RPC ===
* provides name of procedure to invoke
* encoding can be defined by xsd or SOAP Encoding - SOAP Encoding definition is lacking - may have interoperability issues
* tightly coupled - WSDL defines sending and return parameters
* synchronous

=== Document-style ===
* literal encoding - format specified by xsd
* loosely coupled - document driven - parameters sent as a document (instead of a set of parameters)
* contents of message determine how to process
* may be synchronous or asynchronous

== Static invocation ==
* stubs generated from WSDL
* WSDL doesn't need to be parsed each time

== Dynamic invocation ==
* clients generated at runtime
** dynamic proxy - dynamic binding
* changes to WSDL do not break the client

== MTOM ==
Message Transmission Optimization Mechanism
http://en.wikipedia.org/wiki/MTOM
method of efficiently sending binary data to and from web services. It uses XOP (XML-binary Optimized Packaging)
Replaces MIME and DIME
* WSDL interface now contains the binary definition
* MTOM may be used in a document literal wrapped WSDL
* MTOM doesn't force attachments as Soap with attachments does

* https://jax-ws.dev.java.net/guide/Binary_Attachments.html
* http://www.w3.org/TR/soap12-mtom/

== RESTful Web Services ==
JAX-WS support REST but REST isn't good for tooling Sun's [http://research.sun.com/spotlight/2006/2006-04-24-TR153.html WADL technical report] https://wadl.dev.java.net/ Web Application Description Language (WADL)] is an attempt to solve the tooling problem.
[http://java.sun.com/developer/technicalArticles/WebServices/restful/ jax-ws and REST]
[http://www.infoq.com/articles/rest-introduction intro to REST]
* everything (object you want to expose should have an id)
* HATEOAS Hypermedia as the engine of application state
** use of links to move an application from one state to another
** deliver the representation as a (resource graph) tree of links that enable access/state changes to the resource - enable discovery from an initial point
* GET
** retrieve - idempotent (same result when repeated)
* PUT
** update - idempotent
* DELETE
** destroy - idempotent
* POST
** create - not idempotent
* create urls for operations to allow more object methods to map to these four HTTP methods

Triangle representing how urls can be constructed

Data Types
/ \
Operations -- Instances

State should not need to be part of a conversation. i.e. each request should be stateless in the context of the previous request.

No service definition for RESTful service i.e. no WSDL equivalent exists

Can use jaxb or jaxp see [http://weblogs.java.net/blog/mhadley/archive/2006/03/restful_web_ser_1.html jaxb REST blog]

Example: [http://kenai.com/projects/suncloudapis/pages/HelloCloud Suns cloud REST interface]

== EBXML ==
* Not widely adopted
* Uses attachments for payload, not defined in the same self describing way as wsdl
** requires endpoints know and understand the ebMS SOAP extensions
* Adds security, reliability
* includes a repository unlike uddi

Web Services - Revision history

Martin: Created page with "= Web Services = == References == Jboss users guide to web services http://www.jboss.org/jbossws/docs/jaxws_userguide-2.0/index.html == Definitions == URI - uniform resource..."