Documentation

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§The template engine

§A type safe template engine based on Scala

Play comes with Twirl, a powerful Scala-based template engine, whose design was inspired by ASP.NET Razor. Specifically it is:

Note: Even though the template engine uses Scala as expression language, this is not a problem for Java developers. You can almost use it as if the language were Java.

Remember that a template is not a place to write complex logic. You don’t have to write complicated Scala code here. Most of the time you will just access data from your model objects, as follows:

myUser.getProfile().getUsername()

Parameter types are specified using a suffix syntax. Generic types are specified using the [] symbols instead of the usual <> Java syntax. For example, you write List[String], which is the same as List<String> in Java.

Templates are compiled, so you will see any errors in your browser:

§Overview

A Play Scala template is a simple text file that contains small blocks of Scala code. Templates can generate any text-based format, such as HTML, XML or CSV.

The template system has been designed to feel comfortable to those used to working with HTML, allowing front-end developers to easily work with the templates.

Templates are compiled as standard Scala functions, following a simple naming convention. If you create a views/Application/index.scala.html template file, it will generate a views.html.Application.index class that has a render() method.

For example, here is a simple template:

@(customer: Customer, orders: List[Order])

<h1>Welcome @customer.name!</h1>

<ul>
@for(order <- orders) {
  <li>@order.getTitle()</li>
}
</ul>

You can then call this from any Java code as you would normally call a method on a class:

Content html = views.html.Application.index.render(customer, orders);

§Syntax: the magic ‘@’ character

The Scala template uses @ as the single special character. Every time this character is encountered, it indicates the beginning of a dynamic statement. You are not required to explicitly close the code block - the end of the dynamic statement will be inferred from your code:

Hello @customer.getName()!
       ^^^^^^^^^^^^^^^^^^
          Dynamic code

Because the template engine automatically detects the end of your code block by analysing your code, this syntax only supports simple statements. If you want to insert a multi-token statement, explicitly mark it using brackets:

Hello @(customer.getFirstName() + customer.getLastName())!
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                          Dynamic Code

You can also use curly brackets, to write a multi-statement block:

Hello @{val name = customer.getFirstName() + customer.getLastName(); name}!
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                  Dynamic Code

Because @ is a special character, you’ll sometimes need to escape it. Do this by using @@:

My email is bob@@example.com

§Template parameters

A template is like a function, so it needs parameters, which must be declared at the top of the template file:

@(customer: models.Customer, orders: List[models.Order])

You can also use default values for parameters:

@(title: String = "Home")

Or even several parameter groups:

@(title:String)(body: Html)

§Iterating

You can use the for keyword, in a pretty standard way:

<ul>
@for(p <- products) {
  <li>@p.getName() ([email protected]())</li>
}
</ul>

Note: Make sure that { is on the same line with for to indicate that the expression continues to next line.

§If-blocks

If-blocks are nothing special. Simply use Scala’s standard if statement:

@if(items.isEmpty()) {
  <h1>Nothing to display</h1>
} else {
  <h1>@items.size() items!</h1>
}

§Declaring reusable blocks

You can create reusable code blocks:

@display(product: models.Product) = {
  @product.getName() ([email protected]())
}

<ul>
@for(product <- products) {
  @display(product)
}
</ul>

Note that you can also declare reusable pure code blocks:

@title(text: String) = @{
  text.split(' ').map(_.capitalize).mkString(" ")
}

<h1>@title("hello world")</h1>

Note: Declaring code block this way in a template can be sometime useful but keep in mind that a template is not the best place to write complex logic. It is often better to externalize these kind of code in a Java class (that you can store under the views/ package as well if you want).

By convention a reusable block defined with a name starting with implicit will be marked as implicit:

@implicitFieldConstructor = @{ MyFieldConstructor() }

§Declaring reusable values

You can define scoped values using the defining helper:

@defining(user.getFirstName() + " " + user.getLastName()) { fullName =>
  <div>Hello @fullName</div>
}

§Import statements

You can import whatever you want at the beginning of your template (or sub-template):

@(customer: models.Customer, orders: List[models.Order])

@import utils._

...

To make an absolute resolution, use root prefix in the import statement.

@import _root_.company.product.core._

If you have common imports, which you need in all templates, you can declare in build.sbt

TwirlKeys.templateImports += "org.abc.backend._"

§Comments

You can write server side block comments in templates using @* *@:

@*********************
 * This is a comment *
 *********************@

You can put a comment on the first line to document your template into the Scala API doc:

@*************************************
 * Home page.                        *
 *                                   *
 * @param msg The message to display *
 *************************************@
@(msg: String)

<h1>@msg</h1>

§Escaping

By default, dynamic content parts are escaped according to the template type’s (e.g. HTML or XML) rules. If you want to output a raw content fragment, wrap it in the template content type.

For example to output raw HTML:

<p>
  @Html(article.content)
</p>

Next: Common use cases