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From "Ivelin Ivanov" <ive...@apache.org>
Subject Re: Antwort: Re: Creating dynamic content using JSP like Tag implementation
Date Mon, 29 Apr 2002 13:19:09 GMT

Volker,

I don't think that an iterator tag would be of great practical importance
for Cocoon,
but it would be certainly interesting to demonstrate the technique that one
would use
to create a tag which reevaluates its body.

Since many of the tags share similar code in XMLFormTransformer, I am not
sure that splitting it up in 10 classes would be necessarily cleaner.
However I am open to suggestions.


Ivelin


----- Original Message -----
From: <volker.schmitt@basf-it-services.com>
To: <cocoon-dev@xml.apache.org>
Sent: Sunday, April 28, 2002 8:28 AM
Subject: Antwort: Re: Creating dynamic content using JSP like Tag
implementation


>
>
> Ivelin,
>
> we have for the moment no implementation of a IteratorTag. I thought often
> about an implementation and I think that we can implement it similarly as
in the
> current
> JSP Jakarta taglib Implemtierung (http://jakarta.apache.org/taglibs/). If
you
> are interested, look at the current CVS "jakarta-taglibs" package
> "org.apache.taglibs.standard.tag.common.xml" or the documentation in
> "standard/doc/web/XML_ControlFlow_FunctionalDescription_1_EA2.html".
> The differences between a Transformer and the SAX Tag implementation is,
that it
> is more modular and avoid the "if else" cascades in a transformer
> implementation.
> In our applications we have a lot of application specific Tag, not to much
> generic Tag. Generic Tags we have, are Tags like i18n translation,
comboboxes
> for day, month, year ....
>
> If you like, I can make a suggestion for a IteratorTag implementation
based on
> the JSP design of the "JSP Standard Tag Library" which uses SAX instead of
> Streams ;-) I can also make a proposal for a XFormsTransformer implemented
as a
> set of Tag's, but for this, I need to have a more detailed look at the
current
> implementation.
>
> Regards,
>
> Volker
>
>
>
> |--------+----------------------->
> |        |          "Ivelin      |
> |        |          Ivanov"      |
> |        |          <ivelin@apach|
> |        |          e.org>       |
> |        |                       |
> |        |          27.04.2002   |
> |        |          06:39        |
> |        |          Bitte        |
> |        |          antworten an |
> |        |          cocoon-dev   |
> |        |                       |
> |--------+----------------------->
>
>---------------------------------------------------------------------------
-|
>   |
|
>   |       An:     cocoon-dev@xml.apache.org
|
>   |       Kopie:  (Blindkopie: Volker Schmitt/BASF-AG/BASF)
|
>   |       Thema:  Re: Creating dynamic content using JSP like Tag
|
>   |       implementation
|
>
>---------------------------------------------------------------------------
-|
>
>
>
>
>
>
> Volker,
>
> After I looked at the implementation of the TagTransformer code, I
realized
> that it's very similar to the AbstractSaxTransformer class currently in
> Cocoon2.
>
> Can you elaborate a bit on the differences and provide a non trivial
example
> of a tag.
> For example how would an iterator tag look like.
> If you see the XMLForm namespace tags, the repeat tag works like this:
>
> <xf:repeat nodeset="user/favorite">
>   <xf:output ref="url">
>     <xf:caption>URL :</xf:caption>
>   </xf:output>
> </xf:repeat>
>
>
> If you have time, please look at the XMLFormTransformer in Scratchpad
which
> extends AbstractSaxTransformer and advise if it could be written more
> optimally as a set of tags.
>
>
> Thanks,
>
> Ivelin
>
>
>
> ----- Original Message -----
> From: <volker.schmitt@basf-it-services.com>
> To: <cocoon-dev@xml.apache.org>
> Sent: Friday, April 26, 2002 11:38 AM
> Subject: Creating dynamic content using JSP like Tag implementation
>
>
> >
> >
> > Hi all,
> >
> > let me start with a short introduction of my company and what we have
done
> so
> > far.
> > Before being founded on April 1, 2001 as BASF IT Services we were an
> integrated
> > part of BASF Aktiengesellschaft in Ludwigshafen, Germany and BASF
Computer
> > Services in Europe. We focus on high-quality IT-Development and Services
> > throughout Europe. E-Commerce is one of our businesses we have been
> working with
> > since several years and where we are very experienced in developing
> successful
> > solutions for BASF.
> > End of 2000, BASF started their global E-Commerce initiative named
> > "WorldAccount", focusing on a worldwide and integrated extranet platform
> for
> > their customers (have a look at it: http://worldaccount.basf.com).
> > To realize such a complex solution we had the idea to develop a
publishing
> > framework which should also cover issues like session management,
> multi-language
> > support, layout and security. After evaluating Cocoon2 we decided to
base
> on the
> > concepts of Avalon and the basic interfaces of Cocoon2, but due to its
> pre-alpha
> > version we needed to do some additional development (interpreted
Sitemap,
> > LayoutTransformer, RequestProcessor, ValidationEngine, ErrorHandler,
> simple
> > module concept  (like Blocks but really simple)......)
> > One other example: instead of using XSP-Logicsheets we developed a
> > tag-implementation similar to JSP-tags, but which uses a SAX-pipeline
> instead of
> > an output stream. The tags are interpreted during run-time by the
> appropriate
> > tag-transformer.
> > We needed approx. half a year to develop this framework where then the
> > WorldAccount functionalities could be placed on top and finally could
> go-live in
> > the 3rd quarter of 2001. In the last few months we transferred our
> framework to
> > Cocoon2 and would now like to present some of our solutions to the Open
> Source
> > community, hoping we can help to become Cocoon2 even more powerful and
> > successful than it already is.
> >
> > Ok, lets start with the Java-Code ;-) also part of the attachment.
> > The Tag Interface:
> >
> > public interface Tag extends XMLPipe, Component
> > {
> >     String ROLE = Tag.class.getName();
> >
> >     /**
> >      * Evaluate body content
> >      * Valid return value for doStartTag.
> >      */
> >     int EVAL_BODY = 0;
> >
> >     /**
> >      * Skip body evaluation.
> >      * Valid return value for doStartTag.
> >      */
> >     int SKIP_BODY = 1;
> >
> >     /**
> >      * Continue evaluating the page.
> >      * Valid return value for doEndTag().
> >      */
> >     int EVAL_PAGE = 2;
> >
> >     /**
> >      * Process the end tag for this instance.
> >      *
> >      * @returns EVAL_PAGE.
> >      * @throws SAXException.
> >      */
> >     int doEndTag(String namespaceURI, String localName, String qName)
> throws
> > SAXException;
> >
> >     /**
> >      * Process the start tag for this instance.
> >      * <p>
> >      * The doStartTag method assumes that parent have been set.
> >      * It also assumes that any properties exposed as
> >      * attributes have been set too. When this method is invoked, the
body
> >      * has not yet been evaluated.
> >      *
> >      * @returns EVAL_BODY or SKIP_BODY.
> >      */
> >     int doStartTag(String namespaceURI, String localName, String qName,
> > Attributes atts) throws SAXException;
> >
> >     /**
> >      * Get the parent (closest enclosing tag handler) for this tag
> handler.
> >      *
> >      * @returns the current parent or null if none.
> >      */
> >     Tag getParent();
> >
> >     /**
> >      * Set the <code>SourceResolver</code>, objectModel <code>Map</code>
> >      * and sitemap <code>Parameters</code> used to process the request.
> >      */
> >     void setup(SourceResolver resolver, Map objectModel, Parameters
> parameters)
> >     throws SAXException, IOException;
> >
> >     /**
> >      * Set the parent (closest enclosing tag handler) of this tag
handler.
> >      * Invoked by the implementation object prior to doStartTag().
> >      *
> >      * @param parent The parent tag or null.
> >      */
> >     void setParent(Tag parent);
> > }
> >
> >
> >
> > The Tag Implementation works like a JSP Tag but generate SAX output.
> >
> > Simple Tag Implementation:
> >
> > public class XMLDateTag extends AbstractTag
> > {
> >     public int doStartTag(String namespaceURI, String localName,
> >                           String qName, Attributes atts)
> >     throws SAXException
> >     {
> >         String date = new Date(System.currentTimeMillis()).toString();
> >         characters(date.toCharArray(), 0, date.length());
> >         return EVAL_BODY;
> >     }
> > }
> >
> > In the current implementation the Tag's are configured in cocoon.xconf.
> All Tags
> > are managed by a ComponentSelector and grouped by a namespace (name of
the
> > taglib Element). We are using URN's as namespace. The name of a tag is
> then
> > mapped to it's implementation.
> >
> > Example configuration:
> >
> > <component role="org.apache.cocoon.xml.taglib.TagSelector"
> >
class="org.apache.cocoon.components.ExtendedComponentSelector">
> >   <taglib name="urn:apache:taglib:general"
> >           class="org.apache.cocoon.components.ExtendedComponentSelector"
> > logger="sitemap.tag">
> >       <tag name="date"
> class="org.apache.cocoon.xml.taglib.general.XMLDateTag"
> > logger="sitemap.tag.xmldate" />
> >       <tag name="..."  class="..." />
> >   </taglib>
> >   <taglib name="urn:apache:taglib:... />
> >       <tag ..... />
> >   </taglib>
> > </component>
> >
> > Simple example page:
> >
> > <page>
> >  <title xmlns:tag="urn:apache:taglib:general">Hello</title>
> >  <content>
> >   <para>This is my first Cocoon page!</para>
> >   <para>Today, <tag:date /></para>
> >  </content>
> > </page>
> >
> > How does it work?
> >
> > In the pipeline you need to configure the TagTransformer and add it to
> your
> > pipeline. Set the pool-min to "0" because of a bug in excalibur, instead
> you run
> > in a endless loop.
> >
> > <map:transformer name="tag"
> > src="org.apache.cocoon.transformation.TagTransformer"
> >                  pool-max="64" pool-min="0" pool-grow="2"
> > logger="sitemap.transformer.tag">
> >       <transformer-hint>tag</transformer-hint>
> > </map:transformer>
> >
> > The TagTransformer looks if the namespace of an element belongs to a
> configured
> > taglib namespace and tag name (see startElement). If it founds a Tag,
this
> Tag
> > is dynamically inserted to the current SAX-Pipeline and the doStartTag
> method is
> > called. If the Tag implements some "SAX Event handling" methods, the Tag
> is able
> > to work like a Transformer. The default behavior is a XMLPipe. The
> doEndTag
> > method is called if the endElement SAX Event is called (see endElement
of
> > TagTransformer) and the Tag is removed from the pipeline. In the
> doStartTag
> > and/or in the doEndTag you can emit additional SAX events to the
Pipeline
> (see
> > XMLDateTag which only sends the current date). Tags can be nested and a
> inner
> > Tag can get a reference to the parent Tag (getParent method).
> > The TagTransformer can be configured with a "transformer-hint". If the
> > TagTransformer add a Tag to the Pipeline the Transformer which belongs
to
> this
> > hint is also add to the pipeline (after the Tag). If this hint is the
> > TagTransformer itself, a Tag can send out other Tags which are automatic
> > interpreted again.
> >
> > Any comments ?
> > If you find this usefull, is it possible that a committer put this to
> scratchpad
> > ?
> >
> > Thanks Volker
> >
> > (See attached file: source.zip)
> >
>
>
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