Javalin rendering

The javalin-rendering artifact is an optional module for the Javalin web framework that provides a simple way to render HTML using popular template engines. The javalin-rendering artifact includes default implementations for several template engines, including JTE, Mustache, Velocity, Pebble, Handlebars, and Thymeleaf, but you also have to add the dependency for the template engine you want to use.

Adding dependencies

<dependency>
    <groupId>io.javalin</groupId>
    <artifactId>javalin-rendering</artifactId>
    <version>5.5.0</version>
</dependency>
<dependency>
    <groupId><!-- template engine group --></groupId>
    <artifactId><!-- template engine artifact --></artifactId>
    <version><!-- template engine version --></version>
</dependency>

implementation("io.javalin:javalin-rendering:5.5.0")
// template engine dependency

Using the plugin

All the template engines look for templates/markdown files in src/resources/templates, and the correct rendering engine is chosen based on the extension of your template. Javalin will automatically initialize the template engine of an included dependency for you, but you can also initialize it yourself (if you want to configure it).

You can also register your own rendering engine.

Rendering a template

Once you have added the dependencies for the template engine you want to use, all you have to do is call ctx.render() with the path to your template file (and optionally a model):

ctx.render("/templateFile.ext", model("firstName", "John", "lastName", "Doe"));

ctx.render("/templateFile.ext", mapOf("firstName" to "John", "lastName" to "Doe"))

Configuring a template engine

If you wish to configure a template engine (for example, to set a root directory for your template files), all init methods receive optional parameters with their template engine configurations:

JavalinFreemarker.init(configuration: Configuration?)
JavalinJte.init(templateEngine: TemplateEngine?, isDevFunction: ((Context) -> Boolean)?)
JavalinMustache.init(mustacheFactory: MustacheFactory?)
JavalinPebble.init(pebbleEngine: PebbleEngine?)
JavalinThymeleaf.init(templateEngine: TemplateEngine?)
JavalinVelocity.init(velocityEngine: VelocityEngine?)
JavalinCommonmark.init(htmlRenderer: HtmlRenderer?, parser: Parser?)

Registering a new engine:

JavalinRenderer.register(new JavalinPebble(), ".peb", ".pebble");

JavalinRenderer.register((filePath, model, ctx) -> {
    return MyRenderer.render(filePath, model, ctx);
}, ".ext");

JavalinRenderer.register(JavalinPebble(), ".peb", ".pebble")

JavalinRenderer.register({ filePath, model, ctx ->
    MyRenderer.render(filePath, model, ctx)
}, ".ext")

Good to know

Please consult the documentation for that particular template engine to learn how to use them, these kinds of settings are not handled through Javalin.

If you need to configure settings beyond what’s available in JavalinTemplateEngine.init (for example, to set a custom file extension), you have to write your own implementation and register it using JavalinRenderer.register.

Note that if you’re using JavalinRenderer, these are global settings, and cannot be configured per instance of Javalin.