1. An XML Web Publishing Framework From the Apache Project
Cocoon
An XML Web Publishing Framework From the Apache Project
Roland Schweitzer

2. Today’s Topics: Definitions Motivation
Required Tools (Java, Apache Tomcat and Cocoon)
Basic Cocoon Operation
Matchers, Generators, Transforms and Serializers. Oh My!
sitemap.xml glues it all together.
6 August 2002
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3. Cocoon
An XML-based WWW publishing framework implemented as a Java Servlet.
Web site content stored in XML files (or RDBMS, LDAP Server or other source) is transformed (mostly via XSLT) into new XML files (to exclude certain info for example) and then serialized into human usable output (like an HTML or PDF file).
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4. Reusable Content
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5. Motivation for using Cocoon
We distribute climate data
Users (including scientists) find data via public search engines like google
Public search engines index HTML content
NOAA and other scientific organization use special purpose search engines that use FGDC (or DIF derived from FGDC)
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6. Motivation continued
These facts add up to maintaining separate “documents” for each purpose
XML and Cocoon offers a (yet another potential) way out of the morass of many special purpose document collections
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7. Suppose info was stored as XML
<page>
<title>Reynolds Sea Surface Temperature </title>
<prefix>data.sst</prefix>
<abstract>
<para>
The optimum interpolation (OI) SST analysis…
</abstract>
<contact>
<name>CDC Data Management Personel</name>
<address1>325 Broadway</address1>
<phone>(303) </phone>
</contact> …
</page>
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8. The Power of XML Content
Can be parsed with standard XML tools
Can be easily used for another purpose besides the Web
Can be written with powerful XML GUI tools (e.g. XML spy)
(Might be) easier to maintain
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9. Reusable Content
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10. Schematic of the Solution Using Cocoon
Cocoon Some other process
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11. Required Tools
On Solaris 7 and 8 I have used the binary distributions of:
Java (java.sun.com)
Tomcat (
Cocoon (xml.apache.org)
At this time, these are the latest releases.
Follow the installation instructions for each package.
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12. Basic Operation Cocoon is based on pipelines: A Bit of Software
XML File
New XML File
A Bit of Software
New XML File
Info to client
(e.g HTML to browser)
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13. Basic Operation
Cocoon is based on pipelines. An XML document is pushed through a pipeline consisting of one Generator (read a file, create a file from an LDAP server, etc.), zero or more Transforms (for example, to leave out sensitive information for external users) and ends with a Serializer that transforms the XML to binary or character data for consumption by the client (Web browser).
The entire site could use only one pipeline.
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14. Basic Operation If you need more than one pipeline…
Matchers (wildcard and regular expression) and Selectors (Boolean expressions) can be used to control the pipeline used to process the XML content.
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15. Components
Matchers, Generators, Transforms and Serializers are all Cocoon Components.
Pipelines are build out of Components.
Components are declared and pipelines are constructed in the sitemap.xmap file.
The “Bit of Software” needed for each Component is provided by Cocoon or built by you.
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16. Components (Matchers)
Suppose you wanted these URI patterns to be handled by cocoon:
For example the wildcard patterns:
and
could result in two pipelines with two different outputs types.
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17. Components (Matchers)
Need a “bit of software” that looks at:
Matches the the URL
And the extension “.html”
Extracts the wildcard part of the URL data.sst
Starts the pipeline to produce HTML output from the data.sst.xml file (the wildcard plus the .xml extension).
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18. The WildCard Matcher We’re in luck!
A Matcher Component already exists in Cocoon to do what we want.
To use a Component we must declare it in the sitemap.xmap file that controls our Cocoon installation.
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19. Declare the WildCard Matcher
In sitemap.xmap configuration file:
<map:matchers default=“wildcard”>
<map:matcher name=“wildcard”
src=
"org.apache.cocoon.matchingWildcardURIMatcher"/> …
</map:matchers>
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20. Use the Matcher on a URI We’ve declared the Matcher Component
Use the Matcher component in our pipeline to grab the * part of the pattern and use it to specify the source XML file that will be send through the pipeline.
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21. Use the Matcher in a Pipeline
This pipeline uses the default Matcher, which is the WildCard Matcher we declared in the previous slide
<map:match pattern=“data/*.html"> <map:generate src=" data/{1}.xml"/>
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22. Now What?
We have successfully declared and used a Matcher to decide which pipeline we will use to process the first of our two examples URIs.
Now we need to declare and use a Generator, which is always the first step of the pipeline.
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23. Components (Generators)
Declare a generator in sitemap.xmap:
<map:generators default=“file”>
<map:generator name=“file” src=
“org.apache.cocoon.generationFileGenerator”/> …
</map:generators>
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24. Use the Generator in a Pipeline
The File Generator was declared as the default.
Its only job is to read the a file from the file system.
<map:pipelines>
<map:pipeline>
<match pattern=“data/*.html”>
<map:generate src=“data/{1}.xml”/> …
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25. Review: Matcher and Generator
Components (Matchers)
Need a “bit of software” that looks at:
Matches the the URL
And the extension “.html”
Extracts the wildcard part of the URL data.sst
Starts the pipeline to produce HTML output from the data.sst.xml file (the wildcard plus the .xml extension).
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26. Review: Pipeline Components
Conditional use of pipeline via the Matcher
One Generator (FileGenerator)
Zero or more Transforms (?)
Ends with a Serializer (?)
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27. Components (Transforms)
Declare a Transform:
<map:transformers default="xslt">
<map:transformer name="xslt“
src="org. apache.cocoon.transformation.TraxTransformer">
<use-request-parameters>
false
</use-request-parameters>
<use-browser-capabilities-db>
</use-browser-capabilities-db>
</map:transformer>
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28. The XSLT Transformer <use-request-parameters>
Different from previous declarations we’ve seen.
This declaration includes two additional configuration parameters.
<use-request-parameters>
<use-browser-capabilities-db>
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29. Add the Transformer to Pipeline
<map:match pattern="*.html"> <map:generate src=" {1}.xml"/>
<map:transform
src=“datastyle/HTMLstyle.xsl"/>
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30. The Stylesheet written in XSLT:
<HTML>
<HEAD>
<TITLE><xsl:value-of select="/page/title"/></TITLE>
</HEAD>
<BODY> …
<xsl:template match="/page/abstract">
<h2>Abstract:</h2>
<xsl:apply-templates select="para"/>
</xsl:template>
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31. Components (Serializers)
The last step of each Pipeline is a Serializer
It consumes XML (in the form of SAX events) and generates a character stream for a client (Web browser, Acrobat Reader, etc.).
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32. Declare the Serializer
In sitemap.xmap:
<map:serializers default="html">
<map:serializer mime-type="text/html" name="html" src=“...HTMLSerializer">
<buffer-size>1024</buffer-size>
</map:serializer>
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33. The Completed Pipeline
<map:match pattern=“data/*.html"> <map:generate src=“data/{1}.xml"/>
<map:transform
src=“datastyle/HTMLstyle.xsl"/>
<map:serialize/>
</map:match>
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34. Pipeline to make PDF output
<map:match pattern=“data/*.pdf"> <map:generate src=“data/{1}.xml"/>
<map:transform
src="stylesheets/FOstyle.xsl"/>
<map:serialize type="fo2pdf"/>
</map:match>
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35. 6 August 2002
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36. http://www.cdc.noaa.gov/cocoon/data/data.sst.html 6 August 2002
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37. http://www.cdc.noaa.gov/cocoon/data/data.sst.pdf 6 August 2002
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38. The Dreaded Demo Demo Data Set Descriptions at CDC. 6 August 2002
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39. Cocoon is all this and more!
Action Components to do complex initialization (e.g. get database connection pool) during pipeline setup.
Resource Components are internal reusable pipeline fragments.
XSP and Logic Sheets offer capabilities similar to JSP with further separation of the logic.
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40. Resources www.apache.org Inside XSLT by Steven Holzner (New Riders)
Java and XSLT by Eric M. Burke (O’Reilly)
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41. Reality Check! We have not (yet) put this system in production.
Still designing the XML representation.
Still learning about using Cocoon with a relational database.
Considering using XSP pages.
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42. Conclusions
Cocoon offers the potential to use and reuse one bit of XML content for many purposes.
Most operations for Web hosting the XML content are built-in to Cocoon.
Unlimited customization by writing your own Components.
Content is easily maintained and separated from presentation.
6 August 2002
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