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: [EMAIL PROTECTED] |
| 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: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
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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