Cocoon: A Framework for Web Services

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Cocoon A Framework for Web Services

• Using Cocoon to consume and produce Web Services

Pankaj Kumar pankaj_kumar_at_hp.com Web Services
Architect, HP Middleware
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Presentation Goals

• Understand Apache Cocoon, Web Services and how
  Cocoon can be used to build
• Web Applications that consume Web Services and
• Web Services that process huge XML documents

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Speakers Qualifications

• More than 12 years of System Programming
  experience
• Development manager in HP E-speak development
• Development manager of HP XML Application
  Frameworks ( Cocoon connection )
• Currently Web Services Architect at HP Middleware
  ( Web Services connection )
• Contributor to Cocoon project
• JAX-RPC and JSR109 Expert Group Member
• Personal web-site http//www.pankaj-k.net

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Presentation Topics

• What is Cocoon?
• Exploring Cocoon
• What are Web Services?
• Cocoon and Web Services
• A Simple Cocoon Web Application

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What is Cocoon?
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Apache Cocoon

• XML based publishing Framework
• An Apache Software Foundation opensource project
• Written in Java, runs as a servlet ( not strictly
  true ! )
• Project Home Page http//xml.apache.org/cocoon
• Started as a simple servlet based XSL styling
  engine for http//java.apache.org site
• Current version is in the second generation of
  evolution
• Designed for scalability ( uses SAX processing )
  -- can process huge documents using small amount
  of memory

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Apache Cocoon ( Contd. )

• Promotes separation of Content, Logic,
  Presentation and Management in web-site design.

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Exploring Cocoon
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Getting Started

• Download Cocoon Distribution from
  http//xml.apache.org/cocoon
• I used Cocoon 2.0.1 for this presentation
• Unzip the distribution file cocoon-2.0.1-bin.zip.
• Drop cocoon.war to webapps directory of your
  Servlet Container
• I used Tomcat 4.0.1 as the Servlet Container
• Start the Servlet Container
• Point your browser to http//localhost8080/cocoon

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Cocoon Welcome Page
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Cocoon Servlet Dirs. Files
Directory for auto mounting sub-sitemaps
Cocoon Configuration file
A sub-sitemap directory
Main sitemap file
Directory for log files
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Cocoon Sitemap

• Why Sitemap ?
• need to de-couple exposed URI space from actual
  location of resources
• need easily changeable specification of
  processing steps
• What does it contain?
• Component declarations
• generators, transformers, serializers, ...
• Resource declarations
• named collection of pipeline components
• Pipeline declarations
• sequential arrangement of components for
  processing

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Cocoon Sitemap ( Contd. )

• A sitemap is an XML file
• Sitemaps are hierarchical -- A sitemap can point,
  explicitly or implicitly, to sub-sitemaps
• A sitemap is translated into a java program and
  is compiled to bytecode
• Changes to sitemaps can be loaded dynamically and
  asynchronously.
• Cocoon community has debated extensively on
  philosophical aspects of Sitemap but nothing
  better has come out ( yet ! ).

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A sample pipeline

• ltmappipelinegt
• ltmapmatch pattern"hello.html"gt
• ltmapgenerate src"docs/samples/hello-page.xml
  "/gt
• ltmaptransform src"stylesheets/page/simple-pa
  ge2html.xsl"/gt
• ltmapserialize type"html"/gt
• lt/mapmatchgt
• ltmapmatch pattern"images/.png"gt
• ltmapread src"resources/images/1.png"
  mime-type"image/png"/gt
• lt/mapmatchgt
• ltmaphandle-errorsgt
• ltmaptransform src"context//stylesheets/syst
  em/error2html.xsl"/gt
• ltmapserialize status-code"500"/gt
• lt/maphandle-errorsgt
• lt/mappipelinegt

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Request Processing By Cocoon

• Request is dispatched to matching pipeline
• Basic pipeline operation
• The generator generates XML content
• Zero or more transformers transform the content
• The serializer writes it to the output stream
• Different Kinds of generators
• File, Directory, XSP, JSP, Stream,
• Different Kinds of transformers
• XSLT, I18N, Log,
• Different Kind of Serializers
• HTML, XML, Text, PDF, SVG, ...

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Dynamic Content from XSP

• lt!-- A simple XSP Page --gt
• ltxsppage language"java
• xmlnsxsphttp//apache.org/xsp gt
• ltpagegt
• lttitlegtA Simple XSP Pagelt/titlegt
• ltcontentgt
• ltparagtdynamically generated listlt/paragt
• ltulgt
• ltxsplogicgt
• for (int i0 i lt 3 i)
• ltligt Item
• ltxspexprgtilt/xspexprgt
• lt/ligt
• lt/xsplogicgt
• lt/ulgt
• lt/contentgt
• lt/pagegt
• lt/xsppagegt

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What Are Web Services?
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Defining Web Services

• Most commonly used definition
• Web Services are
• described in WSDL
• exchange SOAP messages
• use HTTP as transport
• optionally, registered in UDDI registry
• Interaction can happen using RPC style or
  Document Exchange style, synchronously or
  asynchronously
• Knowledge of Implementation language or
  deployment platform is not required for
  interaction.
• Web Services promise Interoperability.

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SOAP 1.1

• XML based protocol for exchange of information
• Encoding rules for datatype instances
• Convention for representing RPC invocations
• Designed for loosely-coupled distributed
  computing
• Used with XML Schema
• Transport independent
• SOAP with Attachments allow arbitrary data to be
  packaged.

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WSDL 1.1
WSDL 1.1 Document Structure

• A WSDL document describes
• What the service can do
• Where it resides
• How to invoke it
• WSDL are like IDL but lot more flexible and
  extensible
• Defines binding for SOAP1.1, HTTP GET/POST and
  MIME
• WSDL descriptions can be made available from an
  UDDI registry

WSDL Document
Types
Messages
PortTypes
Bindings
Services
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What is a Web Services Platform ?

• Environment, tools, libraries and other resources
  for
• Development of web services
• top down -- start with user code and generate
  WSDL
• bottom up -- start with WSDL and generate
  interfaces
• middle out -- a combination
• discovery of service interfaces
• Deployment of web services
• publishing of services
• pre and post processing of SOAP requests,
  responses
• processing requests for WSDL descriptions
• Consumption of Web Services
• discovery of Web Service
• invocation of/interaction with Web Services

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Java Platforms and Standards

• Java Platforms for Web Services
• HP WSP, HP WSR, HP WST
• Apache SOAP 2.2, Apache Axis, UDDI4J, Cocoon
• JWSDK ( Reference Implementation from Sun )
• Emerging Java Standards for Web Services
• JAXM ( Java XML Messaging )
• JAX-RPC ( Java Web Service Client Prog. model)
• JSR 109 ( Java Web Service Prog. Model,
  deployment, ...)
• JAXR ( Java API to access Web Service Registries
  )
• J2EE 1.4 ( J2EE platform for Web Services )
• Java standards promise portability

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Observations on Java Platforms and Standards

• Handle synchronous RPC style Web Services quite
  well
• Not so good at supporting Web Services with
  document exchange style, especially with
  asynchronous interface
• Have difficulty dealing with large data
• Many approaches to build and consume Web Services
  ( but must adhere to wire protocols )
• Standards in many areas are still emerging
• routing, reliable messaging
• security
• transactioning
• ...

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Cocoon and Web Services
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Cocoon as a Presentation Framework for
Web-Services
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Cocoon as a Processing Framework for Web Services
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A Simple Cocoon Web Application
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Problem Statement

• Use Google Web Services API from
  http//www.google.com/apis
• to create a simple web application that accepts a
  search string from user and displays the list of
  result entries.
• Acknowledgement This example is based on the XSP
  contributed by Ugo Cei in Cocoon-dev mailing
  list.

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Application Components

• sitemap.xmap -- Sitemap for this application
• index.html -- HTML file to accept search string
• google.xsp -- XSP file that makes the SOAP call
  to Google Web Service using SOAP logicsheet.
• search-results.xsl -- XSL stylesheet to transform
  SOAP response from Google Web Service to HTML
  page
• Downloadable from
• http//www.pankaj-k.net/sdwest2002/google.zip

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Application Architecture
Google WS
Cocoon Servlet
Browser
http//lthostgt/cocoon/mount/google/
Maps request to index.html
index.html
/search?q...
SOAP request
SOAP response
executes google.xsp
Search results in HTML
Applies search-results.xsl
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Demo Architecture
Cocoon Servlet
Browser
http//lthostgt/cocoon/mount/google/welcome-local
Maps request to index-local.html
index.html
/search-local?q...
Reads google.results
Search results in HTML
Applies search-results.xsl
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Web Application Demo

• Walk through the
• Design, Sources
• and the Demo