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https://github.com/ssorallen/react-play

Render React components in the Play Framework with JDK8's JavaScript engine
https://github.com/ssorallen/react-play

javascript play-framework reactjs

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Render React components in the Play Framework with JDK8's JavaScript engine

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README 

        
React.js on the Play Framework

==============================



* JDK8 shipped with a JavaScript runtime: [Nashorn](http://openjdk.java.net/projects/nashorn/)

* React supports server side rendering via

  [`React.renderToString`](http://facebook.github.io/react/docs/top-level-api.html#react.rendertostring).

* The [Play Framework](http://playframework.com/) is a web framework that runs

  on the JVM



With these powers combined, Play can use the same JavaScript sent to the client

to render its templates on the server.



## To try it out:



1. Install [JDK8](http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html) for your platform

2. Clone this repository

3. Follow the instructions to install and

   [get started with Play 2.3.x](https://playframework.com/documentation/2.3.x/Home)

4. Run the app with `play run`

5. View [http://localhost:9000/](http://localhost:9000/) in your browser



### What am I looking at?



This app is using the JavaScript from my

[React Reddit Client](https://github.com/ssorallen/react-reddit-client) but with

one key, huge, fantastic change: the first view you see is rendered on the

server.



### The magic is in the Nashorn



The part that makes this all work is the Nashorn JavaScript engine that ships

with Java 8. By eval'ing components on the server, React can produce a string

that's rendereable as plain old HTML.



**The server:**



```scala

def index = Action {

  // Pass 'null' to force the correct class loader. Without passing any param,

  // the "nashorn" JavaScript engine is not found by the `ScriptEngineManager`.

  //

  // See: https://github.com/playframework/playframework/issues/2532

  val engine = new ScriptEngineManager(null).getEngineByName("nashorn")



  if (engine == null) {

    BadRequest("Nashorn script engine not found. Are you using JDK 8?")

  } else {

    // React expects `window` or `global` to exist. Create a `global` pointing

    // to Nashorn's context to give React a place to define its global namespace.

    engine.eval("var global = this;")



    // Evaulate React and the application code.

    engine.eval(new FileReader("target/web/web-modules/main/webjars/lib/react/react-with-addons.js"))

    engine.eval(new FileReader("target/web/public/main/javascripts/components/App.js"))



    Ok(views.html.main("React on Play") {

      play.twirl.api.Html(engine.eval("React.renderToString(React.createElement(App));").toString)

    })

  }

}

```



The client receives the same React and App JavaScript files and executes the

same code the server did. Unlike most other use cases, it will be working on

pre-rendered HTML as opposed to an empty container.



**The client:**



```html



  @content




  React.render(

    React.createElement(App, null),

    document.getElementById("application")

  );



```