Template engine (web)

From Wikipedia, the free encyclopedia

Content (from a database), and "presentation specifications" (in a web template), are combined (through the template engine) to mass-produce web documents.

This article is part of
the Web Template Systems series.

Main:

Supplemental:

A (web) template engine is software that is designed to process web templates and content information to produce output web documents. It runs in the context of a template system.

1 Specific types of template engines
2 Typical Features
3 A web template example
4 Benefits of using template engines
5 References
6 See also
7 External links

[edit] Specific types of template engines

Template engine is ordinarily included as a part of a web template system or application framework, and may be used also as preprocessor, filter, or template processor. Currently, template processing software is most frequently used in the context of development for the web.

XSLT is a template processing model designed by W3C. It is designed primarily for transformations on XML data (into web documents or other output).

Programming languages such as Perl, Ruby, C, and Java support template processing either natively, or through add-on libraries and modules. JavaServer Pages (JSP), PHP, and Active Server Pages (ASP with VBScript, JScript or other languages) are examples, themselves, of web template engines.

[edit] Typical Features

Template engines typically include features common to most high-level programming languages, with an emphasis on features for processing plain text.

Such features include:

variables and functions
text replacement
file inclusion (or transclusion)
conditional evaluation and loops

[edit] A web template example

The accompanying illustration depicts a simplified processing model for a typical web template engine. The template engine produces a web page by processing the web template source file along with data from a relational database. The template engine replaces variables with specific values. In the illustration, substitution of $X by the database content (in page 01 "Mother", on page 02 "World").

A web template might look like this:

<html>
   <h1>Hello {$X}</h1>
</html>

With additional template source code ...

templateAssign ('X', 'World');

... or, when specifying the relational database context:

$data[01]='Mother';  $data[02]='World';
templateAssign('X', $data[$i]);

[edit] Benefits of using template engines

encourages organization of source code into operationally-distinct layers (see e.g., MVC)
enhances productivity by reducing unnecessary reproduction of effort
enhances teamwork by allowing separation of work based on skill-set (e.g., artistic vs. technical)