1. Cocoon: A Framework for Web Services
9/18/2018
Cocoon: A Framework for Web Services
Using Cocoon to consume and produce Web Services
Pankaj Kumar
Web Services Architect,
HP Middleware
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2. 9/18/2018
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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3. Speakers’ Qualifications
9/18/2018
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:
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4. Presentation Topics What is Cocoon? Exploring Cocoon
9/18/2018
Presentation Topics
What is Cocoon?
Exploring Cocoon
What are Web Services?
Cocoon and Web Services
A Simple Cocoon Web Application
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5. 9/18/2018
What is Cocoon?
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6. Apache Cocoon XML based publishing Framework
9/18/2018
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:
Started as a simple servlet based XSL styling engine for 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
History:
Cocoon Project was started by Stefano Mazzocchi in 1998.
Reference: An article by Stefano on Cocoon
Running Cocoon:
Cocoon can also be run as a standalone program taking commandline arguments; or
Main Cocoon class can be instantiated from another Java program.
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7. 9/18/2018
Apache Cocoon ( Contd. )
Promotes separation of Content, Logic, Presentation and Management in web-site design.
Four different working contexts (the rectangles):
Management - The people that decide what the site should contain, how it should behave and how it should appear
Content - The people responsible for writing, owning and managing the site content. This context may contain several sub-contexts - one for each language used to express page content.
Logic - The people responsible for integration with dynamic content generation technologies and database systems.
Style - The people responsible for information presentation, look & feel, site graphics and its maintenance.
Five contracts (the lines)
management - content
management - logic
management - style
content - logic
content - style
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8. 9/18/2018
Exploring Cocoon
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9. 9/18/2018
Getting Started
Download Cocoon Distribution from
I used Cocoon for this presentation
Unzip the distribution file cocoon bin.zip.
Drop cocoon.war to webapps directory of your Servlet Container
I used Tomcat as the Servlet Container
Start the Servlet Container
Point your browser to
Preconditions -- You need a Web Browser, Java SDK and a Servlet container on your machine and sufficient disk space. I used:
-- Windows 2000 machine
-- IE 5.0
-- JDK from Sun Microsystems
-- Apache Tomcat 4.0.1
Directory Structure -- unzipping the distribution file creates directory cocoon with subdirectories docs, legal and WAR file cocoon.war.
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10. 9/18/2018
Cocoon Welcome Page
This page is also the entry point for all bundled samples and examples.
A good way to find out various features is to play around with this page.
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11. Cocoon Servlet Dirs. & Files Directory for auto mounting sub-sitemaps
9/18/2018
Cocoon Servlet
Dirs. & Files
Directory for auto mounting
sub-sitemaps
Cocoon Configuration file
A sub-sitemap directory
Sitemaps are hierarchical.
A sub-sitemap can be dynamically added, without modifying the parent sitemap, by moving to directory for auto mounting.
A number of logs are maintained in the WEB-INF\log directory. Very useful for debugging. log-level is specified in file web.xml of Cocoon servlet.
Main sitemap file
Directory for log files
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12. Cocoon Sitemap Why Sitemap ? What does it contain?
9/18/2018
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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13. Cocoon Sitemap ( Contd. )
9/18/2018
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 ! ).
Dynamic loading of sitemap ==> no need to stop and start the Cocoon servlet for changes in the sitemap to become effective.
Asynchronous loading of sitemap ==> The sitemap is read, validated, compiled and loaded in the background, without impacting the response time of the system during this process.
Sitemap Critique:
Sitemap mixes control ( logic ) and management.
Single point of failure.
Hard to maintain.
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14. A sample pipeline <map:pipeline>
9/18/2018
A sample pipeline
<map:pipeline>
<map:match pattern="hello.html">
<map:generate src="docs/samples/hello-page.xml"/>
<map:transform src="stylesheets/page/simple-page2html.xsl"/>
<map:serialize type="html"/>
</map:match>
<map:match pattern="images/**.png">
<map:read src="resources/images/{1}.png" mime-type="image/png"/>
<map:handle-errors>
<map:transform src="context://stylesheets/system/error2html.xsl"/>
<map:serialize status-code="500"/>
</map:handle-errors>
</map:pipeline>
Processing of XML within a pipeline can be considered as flow of water in a river. XML SAX events pass through the pipeline components one after another.
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15. Request Processing By Cocoon
9/18/2018
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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16. Dynamic Content from XSP
9/18/2018
Dynamic Content from XSP
<!-- A simple XSP Page -->
<xsp:page language="java”
xmlns:xsp=“ >
<page>
<title>A Simple XSP Page</title>
<content>
<para>dynamically generated list:</para>
<ul>
<xsp:logic>
for (int i=0; i < 3; i++) {
<li> Item
<xsp:expr>i</xsp:expr>
</li> }
</xsp:logic>
</ul>
</content>
</page>
</xsp:page>
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17. What Are Web Services? 9/18/2018
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18. Most commonly used definition:
9/18/2018
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.
Interoperability => Ability of a program running within one environment ( programming language, h/w platform, OS, …) to communicate, by invoking method calls or exchanging messages, to programs running within another environment.
Portability => Ability of a program to run within different environments.
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19. SOAP 1.1 XML based protocol for exchange of information
9/18/2018
SOAP 1.1
SOAP 1.1 Message Structure
SOAP
Envelope
[Header
Element]
Header
Entries
Body
Element
[Fault
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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20. WSDL 1.1 A WSDL document describes
9/18/2018
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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21. What is a Web Services Platform ?
9/18/2018
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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22. Java Platforms and Standards
9/18/2018
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
HP WSP => HP Web Services Platform
HP WSR => HP Web Services Registry
HP WST => HP Web Services Transactions
JWSDK => Java Web Services Development Kit
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23. Observations on Java Platforms and Standards
9/18/2018
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
...
Large Data --
Large XML fragments within SOAP Body
Huge attachments ( as per SOAP w/ Attachments specification )
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24. Cocoon and Web Services
9/18/2018
Cocoon and Web Services
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25. Cocoon as a Presentation Framework for Web-Services
9/18/2018
Cocoon as a Presentation Framework for Web-Services
Client Tier
Web Tier
Web Services
WS Registry
Enterprise Apps
Servlet Container
Cocoon
Cocoon is a natural fit in the web-tier, between a browser and backend
web-services.
In this configuration, a program running within Cocoon environment
invokes web-services, reformats the obtained data ( for presentation ) and
serves it to the client.
HP has developed the abstraction of XScript within Cocoon processing
model that makes it possible to do pure xml computation within an XSP.
HP has developed the SOAP and UDDI logicsheets ( tag libraries for the XSP
environment ) that make it extremely easy to invoke web-services from
Cocoon environment.
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26. Cocoon as a Processing Framework for Web Services
9/18/2018
Cocoon as a Processing Framework for Web Services
Client Tier
Web Tier
Web Services
WS Registry
Enterprise Apps
Servlet Container
Cocoon P1 P2
It turns out that SAX based processing model of Cocoon is also very
good to build complex web services that
Need to manage state across multiple interactions,
Support asynchronous messaging
Support reliable delivery of messages ….
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27. A Simple Cocoon Web Application
9/18/2018
A Simple Cocoon Web Application
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28. 9/18/2018
Problem Statement
Use Google Web Services API from
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.
HP WSP => HP Web Services Platform
HP WSR => HP Web Services Registry
HP WST => HP Web Services Transactions
JWSDK => Java Web Services Development Kit
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29. Application Components
9/18/2018
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
HP WSP => HP Web Services Platform
HP WSR => HP Web Services Registry
HP WST => HP Web Services Transactions
JWSDK => Java Web Services Development Kit
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30. Application Architecture
9/18/2018
Application Architecture
Cocoon Servlet
Google WS
Browser
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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31. Demo Architecture Browser Cocoon Servlet
9/18/2018
Demo Architecture
Cocoon Servlet
Browser
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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32. Web Application Demo [Walk through the Design, Sources and the Demo]
9/18/2018
Web Application Demo
[Walk through the
Design, Sources
and the Demo]
HP WSP => HP Web Services Platform
HP WSR => HP Web Services Registry
HP WST => HP Web Services Transactions
JWSDK => Java Web Services Development Kit
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