Experiences using Apache Cocoon

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Experiences using Apache Cocoon Matthew
Mascord 21st January 2004
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Slide 1
Structure

• Context
• Survey of Web Architectures
• Apache Cocoon
• Experiences

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Slide 2
Context Publication Archive

• Data-driven system, many output formats
• Small code footprint gt modification easier, so
• Maximize code reuse, integrate with off-the-shelf
  components
• Favour declarative solutions over procedural
• Use open standards
• Separate concerns

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Slide 3
Web Architectures Model 1

• Collection of JSPs/ASPs/PHPs
• Support classes (beans)
• Simple but
• business logic mixed with presentation
• Lots of Java code intermixed with HTML
  (scriplets)
• Difficult to maintain lacks SoC

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Slide 4
Web Architectures Tag Libraries

• Tag libraries bundle common operations
• Coded in Java
• JSTL standardises common tags
• Expression Language to query Beans

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Slide 5
Model 2 In Pictures

• Based on Model-View-Controller (MVC)
• Apache Struts as a very popular framework

Controller
View
Struts Controller
Action Class
JSP
HTTP Request
Model
HTTP Response
Form Bean
Result Bean
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Slide 6
Model 2 - Assessed

• Logic presentation separated but
• can still hack the JSP
• Struts APIs complex
• JSP limited as view e.g. not pipelined
• JSP compilation error reporting still a problem
• JSP tags JSTL can help but tags written in Java
  hard to define tags in terms of other tags.

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Slide 7
XSLT

• Declarative (functional) language for
  transforming XML
• Very powerful expression language XPath
• Transforms XML to many formats TXT, HTML, XML,
  CSV, SVG, PDF (via XSL-FO), MS EXCEL etc etc
• Model 2X proposed to integrate XSLT with Struts
  Model 2 architecture

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Slide 8
Apache Cocoon

• Web development framework built around Separation
  of Concerns (SoC) and component-based development
  (COP)
• Lego -like approach to development minimal
  coding
• XML publishing framework with XSLT and pipelined
  SAX processing
• Data integration framework RDBMS, LDAP, XMLDB
  etc ? HTML, WML, PDF, RTF etc

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Slide 9
Apache Cocoon - Concepts

• Sitemap
• Readers
• Matchers Selectors
• Generators
• Transformers
• Serializers
• Actions
• XSPs Logicsheets

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Slide 10
Cocoon Pipeline Example
ltmappipelinegt ltmapmatch pattern"search"gt ltma
pact type"search"gt ltmapgenerate
type"serverpages" src"xsp/search.xsp"
/gt ltmaptransform src"xsl/search.xsl"/gt ltma
pserialize/gt lt/mapactgt lt/mapmatchgt lt/mappip
elinegt
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Slide 11
Cocoon XML Example
ltpublicationgt lttitlegtFoundation for Future
Database Systemslt/titlegt ltcontributorgt ltpersonn
amegtC J Datelt/personnamegt ltrolegtAUTHORlt/rolegt lt
/contributorgt ltcontributorgt ltpersonnamegtHugh
Darwenlt/personnamegt ltrolegtAUTHORlt/rolegt lt/contr
ibutorgt ltcontributorgt ltpersonnamegtFabian
Pascallt/personnamegt ltrolegtEDITORlt/rolegt lt/contr
ibutorgt lt/publicationgt
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Slide 12
Cocoon XSLT Example
ltxsltemplate match"publication"gt ltpgt Title
ltinput type"text" name"title"
value"title"/gt lt/pgt ltpgt Authors
ltxslfor-each select"contributorrole'AUTHOR'
"gt ltxslvalue-of select"personname"/gt ltxsl
if test"not(position()last())"gt ltxsltextgt,
lt/xsltextgt lt/xslifgt lt/xslfor-eachgt lt/pgt lt/xs
ltemplategt
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Slide 13
Cocoon Example Result
Title Foundation for Future Database
Systems Authors C J Date, Hugh Darwen
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Slide 14
Cocoon Decision to Use

• Many frameworks need to make decision
• Cocoon is mature popular
• Well supported resources, newsgroups, Wiki
• Open Source modular
• Many output formats
• Minimal coding
• RDBMS -gt XML conversion

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Slide 15
Cocoon Usage

• Tomcat DBCP datasource exposed using JNDI
• XSPs logicsheets for each page
• ESQL translates RDBMS data to XML
• Cocoon Actions call BL

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Slide 16
Cocoon - Benefits

• Sitemap pipelines very powerful MVC controller
• Excellent for prototyping
• Extremely customizable nearly all components
  are replaceable
• Ties together disparate data sources
• Delivers content to disparate devices

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Slide 17
Cocoon - Drawbacks

• XSP mixes syntax
• Logicsheets difficult to debug. Like C STL.
• ESQL not ideal
• Tries to do everything (monolithic) gt
  integration challenges
• Aim to use as presentation layer only
• Have separate layer that generates XML

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Slide 18
Conclusions

• Lots of choice too much
• XSLT simplifies presentation layer
• Cocoon provides framework to do XSLT with minimal
  coding
• Keep to the core features

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Slide 19
References

• http//java.sun.com/blueprints/patterns/MVC-detail
  ed.html
• http//www.w3.org/TR/xslt
• http//cocoon.apache.org/2.0/
• http//www.javaworld.com/javaworld/jw-12-1999/jw-1
  2-ssj-jspmvc.html
• http//www.javaworld.com/javaworld/jw-02-2002/jw-0
  201-strutsxslt.html