|
![]() |
![]() JTP (Java Template Pages) is based on XSL stylesheets. The documentation for the specific tags is in the XSL stylesheet section. This section describes how JTP works. JTP lets web designers create active pages without changing the original text. It uses a separate XSL stylesheet to transform the original document into a fancy formatted document. Because the active stylesheet is separate from the passive content, JTP gives designers a tighter focus. When worrying about style, designers can concentrate on the stylesheet. When concentrating on content, designers can focus on the text. JTP makes the input file simpler: it can be plain old HTML. It separates the content (*.jtp) from the style (*.xsl). The tradeoff is that XSL stylesheets are slightly more complicated than JSP active pages. For JSP, scripts execute exactly where they're placed. JTP has to match HTML to script fragments using patterns. JTP works by matching stylesheet patterns to the input HTML, creating the result HTML following the pattern actions. JTP analyzing the input HTML into a structured HTML tree using the XML document object model. For each node, it finds the best pattern in the XSL and applies the action. The action prints to the output HTML.
In this example, we're using a blank stylesheet. Even with a blank stylesheet, Resin does something useful: it prints out all text, removing the tags.
Resin first reads in the JTP file, parsing it like an HTML file. It adds optional tags, like <html> and </p> and forces all HTML tags to be lower case.
Next, Resin starts its matching process at the top. Since the stylesheet is empty, it uses the default rules. The default rules say: process an element's children and print a text node's data.
Resin's JTP can create standard page layout: common backgrounds, navigation, headers and footers. This is a common use for any of the active content creation tools. This example adds two things to the default stylesheet. All elements are copied instead of ignored, and the body of the HTML gets a background and a margin. Copying elements is easy. The copy template matches all elements
For the page template pattern, we use
The translation follows the same order as in the blank stylesheet example. The body rule is used for the body and the copy-element rule is used for every other tag.
All by itself, the template example is cool. But here's something more interesting, creating a custom tag. In this case, we'll just create a simple counter. To use the counter tag, just add it to the JTP file.
Here's the addition to the stylesheet file.
The JavaScript code is between the special expression tags '<#=' and '#>'. Resin will insert the value of the expression into the generated text. The application object is the same as for JSP. In fact, stylesheets can use any of the JSP implicit variables.
Resin actually creates a JSP file after processing a JTP file. It then evaluates the JSP file to create the output HTML. So the actual processing order is:
Here's we're going to take advantage of this by creating a named counter. If the counter has an 'id' attribute, we'll use it at the value of the application variable. Scripts use the counter the same as before:
Here's the patterns to do it. The
The following JSP file is the result. Resin will execute the generated JSP file to produce the result. Because default.xsl was marked as cached, on following requests Resin will merely reexecute 'gen438.jsp'.
The previous example can be rewritten by using more clever XQL patterns. One pattern matches counters with id attributes. Another matches other counters. So the following stylesheet does the same thing as the previous one.
|