JavaTemplates
Play 2.0 使用了一套全新的且真正强大的基于Scala语言的模版引擎, 该模版引擎的设计灵感来源于 ASP.NET 的 Razor . 具体来说就是:
- 结构紧凑、有表现力并且编写流畅: 它把一个文件中需要的键盘输入字符减少到最少, 并且提供一种快速、流畅的编码流程.不同于其他模版语言，新的Play模版引擎不需要你打乱自己的HTML编码，明确书写一些服务器端代码块。新的解析器足够聪明，可以帮你做这些工作.这就使得这种简单、快速和有趣的模版语言更加紧凑和具有表现力.
- 易于学习: it allows you to quickly become productive, with a minimum of concepts. You use simple Scala constructs and all your existing HTML skills.
- 非新语言: we consciously chose not to create a new language. Instead we wanted to enable Scala developers to use their existing Scala language skills, and deliver a template markup syntax that enables an awesome HTML construction workflow.
- 可由各种文本编辑器编写: 编写模版并不需要特定的工具,模版文件可以由任何文本编辑器来进行编写.
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 writeList[String], which is the same asList<String>in Java.
Templates are compiled, so you will see any errors in your browser:
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);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
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)You can use the for keyword, in a pretty standard way:
<ul>
@for(p <- products) {
<li>@p.getName() ($@p.getPrice())</li>
}
</ul>If-blocks are nothing special. Simply use Scala’s standard if statement:
@if(items.isEmpty()) {
<h1>Nothing to display</h1>
} else {
<h1>@items.size() items!</h1>
}You can create reusable code blocks:
@display(product: models.Product) = {
@product.getName() ($@product.getPrice())
}
<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 your want).
By convention a reusable block defined with a name starting with implicit will be marked as implicit:
@implicitFieldConstructor = @{ MyFieldConstructor() }
You can define scoped values using the defining helper:
@defining(user.getFirstName() + " " + user.getLastName()) { fullName =>
<div>Hello @fullName</div>
}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._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>
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