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

26 August 2002OAR Web Shop 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.

36 August 2002OAR Web Shop 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).

46 August 2002OAR Web Shop Reusable Content

56 August 2002OAR Web Shop 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)

66 August 2002OAR Web Shop 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

76 August 2002OAR Web Shop Suppose info was stored as XML Reynolds Sea Surface Temperature data.sst The optimum interpolation (OI) SST analysis… CDC Data Management Personel 325 Broadway (303) …

86 August 2002OAR Web Shop 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

96 August 2002OAR Web Shop Reusable Content

106 August 2002OAR Web Shop Schematic of the Solution Using Cocoon Cocoon Some other process

116 August 2002OAR Web Shop Required Tools On Solaris 7 and 8 I have used the binary distributions of: –Java 1.4.0(java.sun.com) –Tomcat ( –Cocoon 2.0.3(xml.apache.org) At this time, these are the latest releases. Follow the installation instructions for each package.

126 August 2002OAR Web Shop Basic Operation Cocoon is based on pipelines: A Bit of Software XML File New XML File A Bit of Software New XML File A Bit of Software Info to client (e.g HTML to browser)

136 August 2002OAR Web Shop 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.

146 August 2002OAR Web Shop 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.

156 August 2002OAR Web Shop 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.

166 August 2002OAR Web Shop 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.

176 August 2002OAR Web Shop 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).

186 August 2002OAR Web Shop 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.

196 August 2002OAR Web Shop Declare the WildCard Matcher In sitemap.xmap configuration file: <map:matcher name=“wildcard” src= "org.apache.cocoon.matchingWildcardURIMatcher" /> …

206 August 2002OAR Web Shop 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.

216 August 2002OAR Web Shop Use the Matcher in a Pipeline This pipeline uses the default Matcher, which is the WildCard Matcher we declared in the previous slide

226 August 2002OAR Web Shop 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.

236 August 2002OAR Web Shop Components (Generators) Declare a generator in sitemap.xmap: <map:generator name=“file” src= “org.apache.cocoon.generationFileGenerator” /> …

246 August 2002OAR Web Shop 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. …

256 August 2002OAR Web Shop 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).

266 August 2002OAR Web Shop Review: Pipeline Components Conditional use of pipeline via the Matcher One Generator (FileGenerator) Zero or more Transforms (?) Ends with a Serializer (?)

276 August 2002OAR Web Shop Components (Transforms) Declare a Transform: <map:transformer name="xslt“ src="org. apache.cocoon.transformation.TraxTransformer"> false false

286 August 2002OAR Web Shop Different from previous declarations we’ve seen. This declaration includes two additional configuration parameters. The XSLT Transformer

296 August 2002OAR Web Shop Add the Transformer to Pipeline <map:transform src=“datastyle/HTMLstyle.xsl"/>

306 August 2002OAR Web Shop The Stylesheet written in XSLT: … Abstract:

316 August 2002OAR Web Shop 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.).

326 August 2002OAR Web Shop Declare the Serializer In sitemap.xmap: 1024

336 August 2002OAR Web Shop The Completed Pipeline <map:transform src=“datastyle/HTMLstyle.xsl"/>

346 August 2002OAR Web Shop Pipeline to make PDF output <map:transform src="stylesheets/FOstyle.xsl"/>

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386 August 2002OAR Web Shop The Dreaded Demo Demo Data Set Descriptions at CDC.Demo Data Set Descriptions at CDC

396 August 2002OAR Web Shop 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.

406 August 2002OAR Web Shop Resources Inside XSLT by Steven Holzner (New Riders) Java and XSLT by Eric M. Burke (O’Reilly)

416 August 2002OAR Web Shop 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.

426 August 2002OAR Web Shop 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.