SDPL 2002Notes 7: Apache Cocoon1 7 XML Web Site Architecture Example: Apache Cocoon, a Web publishing architecture based on XML technology

SDPL 2002 Notes 7: Apache Cocoon 1

7 XML Web Site Architecture7 XML Web Site Architecture

Example:Example: Apache Cocoon Apache Cocoon, a Web publishing , a Web publishing architecture based on XML technologyarchitecture based on XML technology

http://xml.apache.org/cocoonhttp://xml.apache.org/cocoon

– Apache: "XML publishing framework"Apache: "XML publishing framework"» runs as a servlet (Java class under the control of a Web runs as a servlet (Java class under the control of a Web

server, to handle incoming HTTP request)server, to handle incoming HTTP request)

– Cocoon 1 (1999 –); not supported anymoreCocoon 1 (1999 –); not supported anymore– Cocoon 2Cocoon 2

» more efficient (based on SAX instead of DOM)more efficient (based on SAX instead of DOM)

» better site administration (with "sitemaps")better site administration (with "sitemaps")


Cocoon Philosophy (1/2)Cocoon Philosophy (1/2)

Separation of concerns with "pyramid of contracts":Separation of concerns with "pyramid of contracts":


Cocoon Philosophy (2/2)Cocoon Philosophy (2/2)

Different responsibilities Different responsibilities different groups different groups– Site administrators, Developers, Site administrators, Developers,

Content producers, Style designersContent producers, Style designers– related declarations separated in different filesrelated declarations separated in different files– supports co-operation of specialised groupssupports co-operation of specialised groups– enhances system modularity and extensibility enhances system modularity and extensibility – allows re-use of solutions to different tasksallows re-use of solutions to different tasks

Content, logic and style merged using XSL Content, logic and style merged using XSL transformationstransformations


Example of typical useExample of typical use

Automatic generation of HTML from (static or generated) Automatic generation of HTML from (static or generated) XML documentsXML documents– client-dependent processing possible, serving, e.g.,client-dependent processing possible, serving, e.g.,

» HTML to "typical" web browsersHTML to "typical" web browsers» WML to WAP-devicesWML to WAP-devices» XML to XML/XSL aware clientsXML to XML/XSL aware clients

– also more sophisticated formatting (FOP also more sophisticated formatting (FOP PDF) PDF) In In Cocoon 1Cocoon 1 processing of a request (by a sequence of processing of a request (by a sequence of

ProcessorsProcessors and a and a FormatterFormatter) controlled by embedded ) controlled by embedded processing instructions (See next)processing instructions (See next)


Example (of Cocoon Example (of Cocoon 11))

Different views of content for different clients:Different views of content for different clients:<?xml version = "1.0"?><?xml version = "1.0"?>





<?<?cocoon-processcocoon-process type="xslt"?> type="xslt"?>

<?xml-stylesheet href="welcome.xsl"<?xml-stylesheet href="welcome.xsl"type="text/xsl"?> type="text/xsl"?> 

<?xml-stylesheet href = "welcome-wml.xsl"<?xml-stylesheet href = "welcome-wml.xsl"

type="text/xsl" type="text/xsl" media="wap"media="wap"?> ?> 

<myMessage><myMessage>

<message>Welcome to XML!</message><message>Welcome to XML!</message>

</myMessage></myMessage>


Example (of Cocoon Example (of Cocoon 11) )

Cocoon 1 configured to handle various Cocoon 1 configured to handle various User-User-AgentsAgents of the HTTP request of the HTTP request– explorer, opera, lynx, netscape, java, wap explorer, opera, lynx, netscape, java, wap

Default style sheet Default style sheet welcome.xslwelcome.xsl specifies specifies generation of HTML, and generation of HTML, and welcome-wml.xsl welcome-wml.xsl processing for WAP devices processing for WAP devices – See nextSee next


Stylesheet Stylesheet welcome-wml.xslwelcome-wml.xsl



<xsl:stylesheet version = "1.0"<xsl:stylesheet version = "1.0"

xmlns:xsl="http://www.w3.org/1999/XSL/Transform"xmlns:xsl="http://www.w3.org/1999/XSL/Transform">>

<xsl:template match = "myMessage"><xsl:template match = "myMessage">

format the result as WML: -->

<xsl:processing-instruction <xsl:processing-instruction name = "name = "cocoon-formatcocoon-format">">type = "text/wml"type = "text/wml"

</xsl:processing-instruction></xsl:processing-instruction>

… …


Style sheet Style sheet welcome-wml.xsl welcome-wml.xsl (2) (2)

<wml><card><wml><card>

<p><p><xsl:value-of select="message"/><xsl:value-of select="message"/></p></p>

<p>This page has been transformed<p>This page has been transformed

from XML into WML by Cocoon's XSLT processor. from XML into WML by Cocoon's XSLT processor.

</p></p>

</card></card>

</wml></wml>

</xsl:template> </xsl:template> 

</xsl:stylesheet></xsl:stylesheet>


Cocoon 2 PipelineCocoon 2 Pipeline

PipelinePipeline: sequence of component interactions to process a request: sequence of component interactions to process a request– typical case:typical case:


Main Components of Cocoon 2Main Components of Cocoon 2 (1/2) (1/2)

GeneratorsGenerators create XML as a SAX stream. E.g: create XML as a SAX stream. E.g:– FileGenerator: XML file FileGenerator: XML file SAX stream SAX stream– HTMLGenerator: HTML file HTMLGenerator: HTML file XHTML (as SAX stream) XHTML (as SAX stream)– … … (and more components can be added)(and more components can be added)

TransformersTransformers manipulate a SAX stream and pass the manipulate a SAX stream and pass the result to the next componentresult to the next component– XSLT Transformer (default)XSLT Transformer (default)– Include Transformers (for XML inclusion via URL)Include Transformers (for XML inclusion via URL)– SQL Transformer (to access a DB, and include results)SQL Transformer (to access a DB, and include results)– … …


Components of Cocoon 2 Components of Cocoon 2 (2)(2)

SerializersSerializers render a SAX stream to some result render a SAX stream to some result format (interpretable by the client)format (interpretable by the client)– HTML Serializer (default)HTML Serializer (default)– XML Serializer, Text SerializerXML Serializer, Text Serializer– PDF/PS Serializer (based on FOP)PDF/PS Serializer (based on FOP)– … …

Components and pipelines declared in a SitemapComponents and pipelines declared in a Sitemap– In XML file In XML file sitemap.xmapsitemap.xmap

(translated to (translated to sitemap_xmap.javasitemap_xmap.java) )


Selecting a PipelineSelecting a Pipeline


Declaring PipelinesDeclaring Pipelines

<map:sitemap<map:sitemap

xmlns:map="http://apache.org/cocoon/sitemap/1.0"xmlns:map="http://apache.org/cocoon/sitemap/1.0">><map:components> … </map:components><map:components> … </map:components>

<map:match pattern="hello.html"><map:match pattern="hello.html"><map:generate src="docs/hello-page.xml" /><map:generate src="docs/hello-page.xml" /><map:transform src="style/simpl2html.xsl"/><map:transform src="style/simpl2html.xsl"/><map:serialize type="html" /><map:serialize type="html" />

</map:match></map:match> … … </map:sitemap></map:sitemap>


Setting up a pipelineSetting up a pipeline


XSP (Extensible Server Pages)XSP (Extensible Server Pages)

Cocoon technology for dynamic contentCocoon technology for dynamic content Procedural code within static document content Procedural code within static document content

– similar with other server pages like JSP or ASPsimilar with other server pages like JSP or ASP <<xsp:pagexsp:page xmlns:xsp=" xmlns:xsp="http://apache.org/xsphttp://apache.org/xsp""

language="java"> ... language="java"> ...– XML document containing tag-based directives for XML document containing tag-based directives for

generating dynamic content at request timegenerating dynamic content at request time– translated by XSP processor into Cocoon Generatorstranslated by XSP processor into Cocoon Generators


XSP: Embedding code into pagesXSP: Embedding code into pages

Example (Example (time.xsptime.xsp); Display the time of day:); Display the time of day:

<xsp:page<xsp:page language="java" language="java" xmlns:xsp="xmlns:xsp="http://www.apache.org/xsphttp://www.apache.org/xsp">">

<xsp:logic><xsp:logic> //Variable for the time of day://Variable for the time of day: Date now = new Date();Date now = new Date(); </xsp:logic></xsp:logic>  <page title="Time of Day"><page title="Time of Day"> <p>It’s now<p>It’s now <xsp:expr><xsp:expr>nownow</xsp:expr></xsp:expr></p></p> </page></page></xsp:page></xsp:page>

XSP processor generates a Generator ...XSP processor generates a Generator ...


XSP page as Generator (fragments of)XSP page as Generator (fragments of)

public class time_xsp extends XSPGenerator {public class time_xsp extends XSPGenerator { … … //Variable for the time of day://Variable for the time of day:

Date now = new Date();Date now = new Date(); public void generate() throws SAXException {public void generate() throws SAXException {

this.contentHandler.startDocument();this.contentHandler.startDocument();AttributesImpl attrs=new AttributesImpl();AttributesImpl attrs=new AttributesImpl();attrs.addAttribute("", "attrs.addAttribute("", "titletitle", "", "titletitle", ",

"CDATA", ""CDATA", "Time of DayTime of Day");");this.contentHandler.startElement("", this.contentHandler.startElement("",

""pagepage", "", "pagepage", attrs);", attrs);… … this.contentHandler.endDocument();this.contentHandler.endDocument();}}


XSP to Generated Content to ResultXSP to Generated Content to Result


Example ResultExample Result

Final HTML page could be:Final HTML page could be:

<html><html><head><title><head><title>Time of DayTime of Day</title></head></title></head><body><body> <h3 style="color: navy; text-align: <h3 style="color: navy; text-align:

center">center">Time of DayTime of Day</h3></h3> <p>It's now <p>It's now Thu Dec 23 20:11:18 PST 1999Thu Dec 23 20:11:18 PST 1999</p></p></body></body></html></html>

OK, but can also separate logic from content OK, but can also separate logic from content (See next)(See next)


Library TagsLibrary Tags

Could replace the preceding with a Could replace the preceding with a library tag:library tag:

...<p>It's now ...<p>It's now <util:date <util:date format="…"/>format="…"/></p> ...</p> ...

– Separation of concerns:Separation of concerns:» programmersprogrammers encapsulate behaviour in dynamic tags encapsulate behaviour in dynamic tags» content authorscontent authors use application-oriented markup to write use application-oriented markup to write

XML documentsXML documents Tag library: set of custom tags Tag library: set of custom tags

– for including code in documentsfor including code in documents– with its own namespacewith its own namespace


Implementation of Tag LibrariesImplementation of Tag Libraries

Tag library implemented by a Tag library implemented by a logic sheetlogic sheet– XSLT stylesheet translating XSP XSLT stylesheet translating XSP XSP XSP– registered in configuration file registered in configuration file cocoon.xconfcocoon.xconf

<util:date format="yy/MM/dd hh:mm:ss aa" /><util:date format="yy/MM/dd hh:mm:ss aa" />

could be implemented by templatecould be implemented by template

<xsl:template match="util:date" ><xsl:template match="util:date" > <<xsp:exprxsp:expr>> formatDate(new Date(), "formatDate(new Date(), "<xsl:value-of <xsl:value-of

select='@format' />select='@format' />");"); </</xsp:exprxsp:expr>>

</xsl:template></xsl:template>


Using Tag LibrariesUsing Tag Libraries


Logic Sheets and Tag LibrariesLogic Sheets and Tag Libraries

Separation of document structure and … Separation of document structure and … – presentation: presentation: stylesheetsstylesheets give give presentation presentation

semanticssemantics to tags to tags– processing: processing: logic sheetslogic sheets give give procedural semanticsprocedural semantics

to tags to tags Built-in tag librariesBuilt-in tag libraries for various dynamic for various dynamic

information:information:– Request: request method & params, protocol, …Request: request method & params, protocol, …– Session: methods for HTTP SessionSession: methods for HTTP Session– ESQL: ESQL: SQL database queries SQL database queries


ESQL: Example (1/2)ESQL: Example (1/2)

<?xml version="1.0" ?><?xml version="1.0" ?>

<xsp:page language="java" <xsp:page language="java" xmlns:xsp="http://www.apache.org/xsp"xmlns:xsp="http://www.apache.org/xsp"

xmlns:xmlns:esqlesql="="http://apache.org/cocoon/SQL/v2http://apache.org/cocoon/SQL/v2">"> <esql:connection><esql:connection> <esql:pool><esql:pool>connectionNameconnectionName</esql:pool></esql:pool> <esql:execute-query><esql:execute-query>

<esql:query><esql:query> SELECT name, addr FROM EmpSELECT name, addr FROM Emp</esql:query></esql:query>

… …


ESQL: Example (2/2)ESQL: Example (2/2)

<esql:results><esql:results><table><table><esql:row-results><esql:row-results>

<tr><td><tr><td><esql:get-string column="<esql:get-string column="namename"/>"/></td></td> <td><td><esql:get-string column="<esql:get-string column="addraddr"/>"/></td></td> </tr></tr></esql:row-results></esql:row-results> </table></table> </esql:results></esql:results> <esql:no-results><esql:no-results> <p>Sorry, no results!</p><p>Sorry, no results!</p> </esql:no-results></esql:no-results> </esql:execute-query></esql:execute-query></esql:connection></esql:connection></xsp:page></xsp:page>


Cocoon used in practise?Cocoon used in practise?

April 2001:April 2001:– 57 Web sites powered by Cocoon 157 Web sites powered by Cocoon 1

April 2002:April 2002:– 34 Web sites powered by Cocoon 134 Web sites powered by Cocoon 1– 17 Web sites powered by Cocoon 2 17 Web sites powered by Cocoon 2

» (34+17 < 57 !)(34+17 < 57 !)

– 9 service providers offering "Cocoon hosting"9 service providers offering "Cocoon hosting"


SummarySummary

Apache CocoonApache Cocoon– "Publishing framework" based on XML technology"Publishing framework" based on XML technology

» esp. on XSLT transformationsesp. on XSLT transformations– Configurable architectureConfigurable architecture

» ComponentsComponents» SitemapSitemap

– XSP and tag libraries for dynamic contentXSP and tag libraries for dynamic content Interesting and promising conceptInteresting and promising concept

– Ideas may survive, perhaps in different systemsIdeas may survive, perhaps in different systems» (E.g. IBM ServletManager?) (E.g. IBM ServletManager?)

Documents

SDPL 2002Notes 7: Apache Cocoon1 7 XML Web Site Architecture Example: Apache Cocoon, a Web publishing architecture based on XML technology