Wicket Velocity

Provides a specialized panel and some related utilities that enables users to work with Apache Velocity and Apache Wicket. Particularly useful for simple CMS like applications.

Contents

Introduction

Velocity brings a templating language to your users. You can let them create conditional markup, use loops and do all other things made possible by Velocity.

Velocity templates look like the following:

#set ($foo = "deoxyribonucleic acid")
#set ($bar = "ribonucleic acid")

#if ($foo == $bar)
  In this case it's clear they aren't equivalent. So...
#else
  They are not equivalent and this will be the output.
#end

Read more about the Velocity template language.

This project allows you to use Velocity templates as a component within your Wicket pages, and let them live next to Wicket components. A typical usecase would be to enable your users to embed Velocity templates in your application and using that as a type of portlet.

The main component for the Veloticy/Wicket integration is the VelocityPanel.

Example

Showing Hello, World using Velocity in a Wicket application, embedded in a Wicket page.

<h2>This is a Velocity template</h2>

<p>The secret message is: $message</p>

In this template we want to replace the string $message with the text “Hello, World!”. $message is Velocity markup denoting a variable that is taken from the context that is provided to the Velocity rendering engine.

To use Velocity in your Wicket pages we provide a VelocityPanel which enables you to generate parts of your page using Velocity markup. Adding the panel to your Wicket page is shown in the following example:

public VelocityPage() {
	HashMap<String, String> values = new HashMap<String, String>();
	values.put("message", "Hello, World!");
	Model<HashMap<String, String>> context = Model.of(values);
	
	UrlResourceStream template = new UrlResourceStream(getClass().getResource("test.html"));
	add(VelocityPanel.forTemplateResource("velocityPanel", context, template));
}

VelocityPanel.forTemplateResource creates a VelocityPanel and sets up the engine such that the context is merged with the template with each render.

The markup of the page is quite simple: adding a VelocityPanel is as simple as using a div and attaching a wicket:identifier to it. The following example shows this.

<!DOCTYPE html>
<h1>This is a test page for Velocity</h1>
<div wicket:id="velocityPanel"></div>

Installing

Installing Wicket Velocity can be done through adding a dependency in your project’s Maven pom, or by putting the wicket-velocity.jar and the required dependencies in your projects classpath.

Using Maven

Add the following dependency to your pom:

<dependency>
    <groupId>org.apache.wicket</groupId>
    <artifactId>wicket-velocity</artifactId>
    <version>1.5.6</version>
</dependency>

Required dependencies

Wicket Velocity requires the following jar files to be on your classpath:

  • Wicket
  • Wicket Velocity
  • Apache Velocity

Check the Apache Velocity project to find out which other dependencies you need.