Jakarta Commons Cookbook

9.6. Using a Simple Templating Language

Problem

You need to produce a parameterized message using a template stored in a file.

Solution

Use Jakarta Velocity and store your template in the filesystem. Jakarta Velocity is a straightforward templating engine with a lightweight syntax similar to the expression language introduced in Recipe 9.2. The following Velocity template is used to create an email:

#set( $customer = $subscription.customer )
#set( $magazine = $subscription.magazine )

$customer.firstName,

Your subscription to ${magazine.title} on
$subscription.endDate.  If you are interested in renewing your subscription,
please click on the following URL, and enter your password:

${magazine.baseUrl}/renew?cust=${customer.id}

This template references a Subscription bean bound to the name subscription. This Subscription object has a customer property and a magazine property, and both of these properties are assigned to a local template variable using the #set directive. To render a Velocity template, the engine is initialized using Velocity.init( ) , a VelocityContext is created and populated, and the template is read with a FileReader . The following code renders this template:

import org.apache.velocity.VelocityContext; import org.apache.velocity.app.Velocity; // Initialize Velocity Velocity.init( ); // Create a context and put our subscription object into the context VelocityContext context = new VelocityContext( ); context.put("subscription", testSubscription( )); // Create a Reader ...