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Java - What's Apache Velocity?

Fri, 03/13/2015 - 17:18 |

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Velocity is a template engine. It is commonly used to populate pages that contains placeholders with data, or to generate source code.

Here's an example of template:

	<html>
	<body>
	Dear Customer,
	<a href="${link}">click on this link to validate your address</a>
	</body>
	</html>

In the above template there is one placeholder. Here, there is the code to read the template and populate it with data:

	
	// Create a template engine
	VelocityEngine ve = new VelocityEngine();
	ve.setProperty(RuntimeConstants.RESOURCE_LOADER, "classpath");
	ve.setProperty("classpath.resource.loader.class", ClasspathResourceLoader.class.getName());

	// Initialize the engine
	ve.init();

	// Read the template from the file system
	Template template = ve.getTemplate("templates/email.txt");

	// Create a context to fill in the placeholders
	VelocityContext ctx = new VelocityContext();

	// Associate real data to a placeholder
	ctx.put("link", "http://www.mywebsite.co.uk");
	
	// Merge the data with the template
	StringWriter sw = new StringWriter();
	template.merge(ctx, sw);

	// Print the final result
	System.out.println(sw.toString());