XML Template Pages encourages web sites to create JSP tag libraries. By putting the JSP creation in stylesheets, you can separate the programming from the web pages. The XTP pages can be simple XML or HTML documents and simply add the custom tags as necessary.

The examples in this section use the full, verbose, XSL and JSP syntax. For those put off by the verbosity, the examples are rewritten in StyleScript examples.

Creating JSP from XTP

Resin creates a JSP file from an XTP file. XTP pages can separate the content (in XML) from the scripting (in XSL). The XSL stylesheets now become a palette of JSP actions you can use just by adding tags.

1. Parse XTP file as HTML
2. Find and parse XSL stylesheet
3. Applying the stylesheet to the XTP, creating a JSP file
4. Execute the JSP file

A trivial example is a named counter. If the counter has an 'id' attribute, we'll use it at the value of the application variable.

XTP pages can use the counter just by adding the tag:

A counter example: <ct:counter id='test'/>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                version="1.0">

<xsl:template match='counter[@id]'>
  <jsp:expression>
     <xsl:text>application.attribute["</xsl:text>
     <xsl:value-of select='@id'/>
     <xsl:text>"]</xsl:text>
  </jsp:expression>
</xsl:template>

<xsl:template match='counter'>
  <jsp:expression>
     application.attribute.counter++
  </jsp:expression>
</xsl:template>

</xsl:stylesheet>

The following JSP file is the result. Resin will execute the generated JSP file to process HTTP requests.

gen438.jsp

A counter example: <jsp:expression> application.attribute["test"]++ <jsp:expression>

Creating JSP flow control

XTP can also generate JSP control. Many programmers like using tags for programming, like Cold Fusion. Here's how to create a basic set of programming tags.

• ct:get prints the value of a variable
• ct:if generates an if statement
• ct:iter loops

An example use might print the HTTP headers.

<ct:iter expr='request.header'/> <ct:get expr='i'/> : <ct:get expr='request.header[i]'/> </ct:iter>

Accept : image/gif, image/png User-Agent : Mozilla/4.5 Accept-Language : en Host : www.caucho.com

Here is the stylesheet:

<xsl:template match='ct:get'>
  <jsp:expression><xsl:value-of select='@expr'/></jsp:expression>
</xsl:template>

<xsl:template match='ct:if'>
  <jsp:scriptlet>
    if (<xsl:value-of select='@expr'/>) {
  </jsp:scriptlet>
    <xsl:apply-templates/>
  <jsp:scriptlet>}</jsp:scriptlet>
</xsl:template>

<xsl:template match='ct:iter'>
  <jsp:scriptlet>
    for (var i in <xsl:value-of select='@expr'/>) {
  </jsp:scriptlet>
    <xsl:apply-templates/>
  <jsp:scriptlet>}</jsp:scriptlet>
</xsl:template>

Copyright © 1998-2002 Caucho Technology, Inc. All rights reserved. Resin® is a registered trademark, and HardCoretm and Quercustm are trademarks of Caucho Technology, Inc.