How to use String as Velocity Template?

Question

What is the best way to create Velocity Template from a String?

I'm aware of Velocity.evaluate method where I can pass String or StringReader, but I'm curios is there a better way to do it (e.g. any advantage of creating an instance of Template).

Answer 1

There is some overhead parsing template. You might see some performance gain by pre-parsing the template if your template is large and you use it repeatedly. You can do something like this,

RuntimeServices runtimeServices = RuntimeSingleton.getRuntimeServices(); StringReader reader = new StringReader(bufferForYourTemplate); Template template = new Template(); template.setRuntimeServices(runtimeServices);  /*  * The following line works for Velocity version up to 1.7  * For version 2, replace "Template name" with the variable, template  */ template.setData(runtimeServices.parse(reader, "Template name")));  template.initDocument(); 

Then you can call template.merge() over and over again without parsing it everytime.

BTW, you can pass String directly to Velocity.evaluate().

Answer 2

The above sample code is working for me. It uses Velocity version 1.7 and log4j.

private static void velocityWithStringTemplateExample() {     // Initialize the engine.     VelocityEngine engine = new VelocityEngine();     engine.setProperty(RuntimeConstants.RUNTIME_LOG_LOGSYSTEM_CLASS, "org.apache.velocity.runtime.log.Log4JLogChute");     engine.setProperty("runtime.log.logsystem.log4j.logger", LOGGER.getName());     engine.setProperty(Velocity.RESOURCE_LOADER, "string");     engine.addProperty("string.resource.loader.class", StringResourceLoader.class.getName());     engine.addProperty("string.resource.loader.repository.static", "false");     //  engine.addProperty("string.resource.loader.modificationCheckInterval", "1");     engine.init();      // Initialize my template repository. You can replace the "Hello $w" with your String.     StringResourceRepository repo = (StringResourceRepository) engine.getApplicationAttribute(StringResourceLoader.REPOSITORY_NAME_DEFAULT);     repo.putStringResource("woogie2", "Hello $w");      // Set parameters for my template.     VelocityContext context = new VelocityContext();     context.put("w", "world!");      // Get and merge the template with my parameters.     Template template = engine.getTemplate("woogie2");     StringWriter writer = new StringWriter();     template.merge(context, writer);      // Show the result.     System.out.println(writer.toString()); } 

A similar so question.