Engines

Definition

A template engine is a class capable of render a specific template language resource, with the properties and message resources provided to the template instance.

Is an implementation class of the cat.albirar.template.engine.service.ITemplateEngine interface.

Since version 3.0.0, a factory is used to render templates. This factory is responsible of find and delegate the render call to a registered template engine.

Library ships with a Thymeleaf Spring Dialect template engine that is auto-registered.

You can add more template engines by adding the corresponding jar to the classpath and configure and register them.

Add a new template engine to your project

In your project, among other libraries, you should to add a dependency to the template engine jar that you want to use.

In your configuration, you should to add the template engine class on the class collection to scan by Spring.

The template engine class should to register itself on factory.

That’s all! You can use templates in the language that the selected template engines can manage.

Develop a new template engine

Dependencies

Among the other dependencies you need, the albirar-template-engine jar dependency should to be added to your project (see dependency info)

Implementation

Create a class that implement the cat.albirar.template.engine.service.ITemplateEngine. Implement the methods as needed.

Your class should to be associated with a specific template language. An identifier is required to do so. A curated selection of identifier string should to be made. In case of Thymeleaf with Spring dialect, the identifier is thymeleaf-spring and is defined as a constant at class cat.albirar.template.engine.service.impl.ThymeleafSpringTemplateEngineImpl.

Is a good practice to expose publicly the string constant with the defined identifier. So, users of your template engine can reference directly this identifier.

Registration

To register a template engine, should to call the register method on cat.albirar.template.engine.service.ITemplateEngineRegistry registry object:

    // ...
    @Autowired
    private ITemplateEngineRegistry registry;

    /**
     * {@inheritDoc}
     */
    @Override
    public void afterPropertiesSet() throws Exception {
        registry.register(this);
    }
    // ...

It’s recommended that the class itself do the registration automatically, on construction time, to avoid the need of registration by users.

In the above example, the template engine class implement the life-cycle interface org.springframework.beans.factory.InitializingBean in order to register itself as a new template engine.

Configuration

If your template engine needs any kind of configuration, you should to create a Configuration class, eligible to import by configuration classes of users.

Although you can register your template with the configuration class, it’s not recommended so in future versions of albirar-template-engine, the registration can be made in a different moment of configuration.

It’s better that template engine class do a self-registration on initializing bean.