Velocity

Velocity is a Java-based template framework which provides the HTML rending engine for Click. Velocity is very easy to learn, simple to use, and is also very capable.

Velocity is an open source Apache project licensed using the Apache Software License.

Velocity's comprehensive online documentation is included in this distribution.

Users Guide - Velocity users guide
Developers Guide - Velocity developers configuration guide
VTL Reference - Velocity Template Language (VTL) reference guide

Object References

With Click you add objects to your page template using the Page's model. You can then access these objects using Velocities $ reference notation. By default the ClickServlet adds the following objects to page templates:

any public Page fields using the fields name
context - the Servlet context path, e.g. /mycorp
cssImports - the CSS imports and style blocks to include in the pages header. Please see PageImports for more details.
format - the Format object for formatting the display of objects.
imports - the CSS and JavaScript imports to include in the pages header. Please see PageImports for more details.
jsImports - the JavaScript imports and script blocks to include in the pages footer. Please see PageImports for more details.
messages - the MessagesMap adaptor for the Page getMessage() method.
path - the path of the page template to render.
request - the pages HttpServletRequest object.
response - the pages HttpServletResponse object.
session - the SessionMap adaptor for the users HttpSession.

In your page templates you can access object references using a dot path notation. For example:

Welcome: $session.user.fullName

Or by using a more explicit Java notation:

Welcome: $session.get("user").getFullName()

Directives

In Velocity directives are prefixed by a # symbol. While references access stuff, directives do stuff. The full set of Velocity directives are:

#if #elseif #else - output conditional on truth of statements.
#foreach - loops through a list of objects.
#macro - allows users to define a Velocimacro (VM), a repeated segment of a VTL template, as required.
#set - establishes the value of a reference.
#include - renders local file(s) that are not parsed by Velocity.
#parse - renders a local template that is parsed by Velocity.
#stop - stops the template engine.