lift-ng

lift-ng is the most powerful, most secure AngularJS backend available today.

The design philosophy of lift-ng is to capture the spirit of both Lift and AngularJS into one package. The result is a secure-by-default framework facilitating powerful and robust client/server interactions for building today's modern web applications. By utilizing Scala's powerfully-flexible language, lift-ng provides a DSL that is natural to use for AngularJS developers and Scala developers alike.

Lift as a backend should appeal to AngularJS developers for the following reasons:

• Lift's templating is unlike most web application frameworks in that it is plain HTML. There is no massaging of your Angular templates to make the framework happy.
• The approach of manipulating the templates on the server by Lift is similar to how you manipulate them on the client with AngularJS. Hence you can manipulate the DOM at the time you know the information, while on the client or earlier while on the server.
• Lift is not MVC. No need to navigate another MVC framework while building with Angular's MVC approach.
• Lift is excellent at slinging HTML and JS. This is precisely what an Angular application needs for a backend.
• Security is handled for you, making it virtually impossible to have your http endpoints successfully attacked. (More on Lift's security)
• Your application will be built on the rock-solid JVM as a time-tested Java servlet on the most mature Scala web framework.

AngularJS as a front end should appeal to Scala and Lift developers for the following reasons:

• JQuery is a pain for non-trivial applications.
• AngularJS does a fantastic job of managing complex client-side interactions for you.
• With lift-ng in particular, you get to utilize Lift's reactive features such as asynchronous comet updates to the client and returning LAFuture[T] results for services.

lift-ng has three major feature areas (click the respective link for details and usage examples):

• Client-Initiated Service Calls: Write secure services in the Scala DSL which can be invoked by the client.
• Server-Initiated Events: Send events to $rootScope or a given $scope easily via familiar AngularJS-like calls to broadcast and emit.
• Client-Server Model Binding: Define your model, declare your scope, and assign a name. Then let lift-ng keep your data in sync between the client(s) and server.

Tutorials

• 15-minute Chat with lift-ng: Screencast by Lift committer/lift-ng contributor Joe Barnes briefly introducing Lift, AngularJS, and lift-ng.
• ScalaDC (Scala + Lift + Angular) is Magic: Screen cast by original lift-ng contributor Doug Roper featuring Scala, Lift, AngularJS, ponies, magic, spastic keyboard pounding, and the first incarnation of lift-ng.

Jump Start

The quickest jump start you can get on lift-ng is via the giter8 template. Otherwise, you should first get started with Lift and configure the project to include the lift-ng module as outlined below.

Configuration

You can configure an existing Lift project to use lift-ng manually. Add lift-ng as a dependency in your build.sbt or Build.scala as appropriate. Optionally add angular from webjars as a dependency if you would like us to manage the delivery of your AngularJS library javascript files. (See Webjar Support below for more details)

libraryDependencies ++= {
  val liftVersion = "3.1.0" // Also supported: "2.5.4", "2.6.3", "3.0.1"
  val liftEdition = liftVersion.value.replaceAllLiterally("-SNAPSHOT", "").split('.').take(2).mkString(".")
  val angularVersion = "1.4.8"
  Seq(
    // Other dependencies ...
    "org.webjars.bower" %  "angularjs"         % angularVersion,
    "net.liftmodules"   %% ("ng_"+liftEdition) % "0.10.2"  % "compile"
   )
}

And invoke Angular.init() in your Boot class (shown here with the default values).

package bootstrap.liftweb

class Boot {
  def boot {
    // Other stuff...
    
    net.liftmodules.ng.Angular.init(
      // Set to true if you plan to use futures. False otherwise to avoid an unneeded comet
      futures = true,

      // Set to the CSS selector for finding your apps in the page.
      appSelector = "[ng-app]",

      // Set to true to include a script tag with the src set to the path for liftproxy.js.
      // Set to false if you want to handle that yourself by referring to the path in
      // net_liftmodules_ng.
      includeJsScript = true,

      // Set to true to include angular.js from org.webjars angularjs
      includeAngularJs = true,

      // Add any additional js modules you want to load in the page from the angularjs webjar
      additionalAngularJsModules = List("animate", "cookies", "loader", "resource", "route", "sanitize", "scenario", "touch"),

      // Set to true to also deliver the angular-csp.css stylesheet on the page
      includeAngularCspCss = true,

      // Set to true to preserve the order of ajax service calls even in the event of server communication failures
      retryAjaxInOrder = true,
      
      // Set to any function mapping a net.liftweb.common.Failure into a Reject
      failureHandler = net.liftmodules.ng.Angular.defaultFailureHandler
    )

    val context:ExecutionContext = // Create context
    net.liftmodules.ng.AngularExecutionContext(context) // Tell lift-ng to use it
  }
}

If you want to handle the downloading of javascript assets yourself with a library such as head.js, then you should initialize with includeJsScript = false. This will prevent our Angular snippet from including the liftproxy.js file. Instead, you can use the global ng_liftmodules_ng object to include the file yourself. You can get the full path to the liftproxy.js file via net_liftmodules_ng.path or get just the lift-ng version alone with net_liftmodules_ng.version.

If you plan to use futures of type scala.concurrent.Future[T], you can dictate the scala.concurrent.ExecutionContext that is implicitly required when lift-ng converts them to LAFuture[T]. By default, we will use scala.concurrent.ExecutionContext.global. To specify a different ExecutionContext, in your Boot.boot invoke the apply method of net.liftmodules.ng.AngularExecutionContext with your preferred ExecutionContext as shown above. For more details about how we handle scala.concurrent.Future[T], read here

Webjar support

As mentioned in the Configuration, lift-ng allows you to smoothly utilize webjars for delivering the angular.js assets. This is the recommended approach as it allows you to update your angular version in the same place as your Scala dependencies. We handle adding the angular version to the asset path for proper cache behavior, and we serve the minified version of the js when you are not running in development mode.

All three flavors of Webjars are supported: Classic, Bower, and NPM.

Classic Webjars

The angularjs Classic Webjar contains all optional angular modules such as animate, cookies, route, etc. Hence you only need to include one jar even if you are using optional modules. However, Classic Webjars are packaged and published by hand, causing you to depend on someone else's manual effort before you can utilize the next version.

Bower and NPM Webjars

The angular/angularjs Bower and NPM Webjars do NOT contain the optional angular modules. You will need to add each one to your build dependencies if you want those served by lift-ng. For instance, if you would like to use the animate module, you should also include it in your dependencies in addition to adding it to additionalAngularJsModules:

libraryDependencies ++= {
  val liftVersion = "2.5.3"
  val liftEdition = liftVersion.substring(0,3)
  val angularVersion = "1.4.7"
  Seq(
    // Other dependencies ...
    "org.webjars.npm" %  "angular"           % angularVersion,
    "org.webjars.npm" %  "angular-animate"   % angularVersion,
    "net.liftmodules" %% ("ng_"+liftEdition) % "0.8.0"  % "compile"
   )
}

The same applies for Bower Webjars.

Note also that for the org.webjars.npm organization, the module name is angular. Angular is published as either angular or angularjs module names under the org.webjars.bower organization.

Supported Versions

lift-ng is built and released to support Lift edition 2.5 with Scala versions 2.9.1, 2.9.2, and 2.10; Lift edition 2.6 with Scala versions 2.9.1, 2.9.2, 2.10, and 2.11; and Lift edition 3.0 with Scala version 2.11. This project's scala version is purposefully set at the lowest common denominator to ensure each version compiles. Automated testing is performed against the latest 2.10/2.5, 2.10/2.6, 2.11/2.6, and 2.11/3.0 Scala/Lift versions for each release of lift-ng.

Usage

Below are usage examples of each of the major features of lift-ng. Be sure to check out the aforementioned sample project or the test project for fully functional examples.

Client-Initiated Service Calls

Most AngularJS backends provide RESTful http endpoints for the application to receive data from the server. lift-ng is certainly no exception by providing a server-side DSL for creating services. Compare the following AngularJS factory

angular.module('lift.pony', [])
  .factory("ponyService", function() {
    return {
      getBestPony: function(arg) {
        // Return the best pony (client-side)
        return BestPony;
      }
    };
  });

... to this lift-ng DSL in Scala

angular.module("lift.pony")
  .factory("ponyService", jsObjFactory()
    .jsonCall("getBestPony", (arg) => {
      // Return the best pony (server-side)
      Full(BestPony)
    })
  )

Both will create an angular module named lift.pony with a service named ponyService with a function named getBestPony, yet the former runs on the client-side, and the latter runs on the server-side.

To flesh out this example completely, you will define a Lift snippet to provide the service to the resulting HTML. Here, we have elected to create an object named NgPonyService, delivering the snippet via Lift's default snippet method name, render

object NgPonyService {
  def render = renderIfNotAlreadyDefined(
    angular.module("lift.pony")
      .factory("ponyService", jsObjFactory()
        .jsonCall("getBestPony", (arg) => {
          // Return the best pony (server-side)
          try {
            Full(BestPony)
          } catch {
            case e:Exception => Failure(e.getMessage)
          }
        })
      )
  )
}

This renderIfNotAlreadyDefined returns a scala.xml.NodeSeq. Hence you will need to add script tags to your target HTML page(s) for the services as well as some plumbing from this module.

<!-- The angular library itself, if not using webjars with includeAngularJs = true -->
<script type="text/javascript" src="/scripts/angular.js"></script>

<!-- Prerequisite stuff the module needs -->
<script data-lift="Angular"></script>

<!-- The NgPonyService snippet defined above -->
<script data-lift="NgPonyService"></script>

<!-- Your angular controllers, etc -->
<script type="text/javascript" src="/scripts/pony.js"></script>

The resulting angular service returns a $q promise. When you call the service, you register callbacks for success, error, and notify (not currently utilized).

angular.module('pony', ['lift.pony'])
  .controller('PonyCtrl', function ($scope, ponyService) {
    $scope.onClick = function () {
      ponyService.getBestPony().then(function(pony) {
        // We have our pony!
        $scope.pony = pony;
      },
      function(err) {
        // No pony!
        $scope.error = err;
      },
      function(progress) {
        // We're still working on getting that pony...
        // Well, not really... we don't use this today...
      });
    };
  });

Mapping Box to Promise

Values requested from the client are always wrapped in a net.liftweb.common.Box. These Box[T] values are mapped to their respective $q promises as follows:

• Full(value) => A resolved promise with the given value.
• Empty => A resolved promise with undefined value.
• Failure(msg) => A rejected promise with the given message value (see Failure Handler below for configuration)

Failure Handler

The Angular.init function has a parameter failureHandler: Failure => Reject. Any service which returns a Failure or throws an Exception will have the failure pass through this function. The returned Reject object is used to reject the respective Promise on the client.

The default implementation of this function simply places the Failure's msg: String into the Reject:

f: Failure => Reject(JString(f.msg))

The Reject case class can accept any JValue, allowing full control over the data used to reject Promises from lift-ng.

JSON Serialization

lift-ng uses Lift JSON for JSON serialization. This JSON serialization is configurable via the implicit Formats trait. Originally, lift-ng always used the DefaultFormats which limited the library's flexibility. Now lift-ng uses DefaultFormats if no other implicit Formats can be found.

However, this does NOT apply to the old JsObjFactory methods jsonCall or future. Because these two were over-loaded with multiple signatures, it is not legal in Scala to provide a default value. In order to avoid a breaking change, we chose not to add an implicit Formats parameter to jsonCall and future.

There are now six methods available for handling the three overrides of each jsonCall and future: defAny, defStringToAny, defModelToAny, defFutureAny, defStringToFutureAny, and defModelToFutureAny. These six have the exact same signature as their respective jsonCall/future methods, except they accept an implicit Formats. If you need to provide a Formats, replace your calls to these new functions.

Regarding these names, please see New interface for JsObjFactory below.

No arguments, string arguments, or case class arguments

Just like with Lift's SHtml.ajaxInvoke, you can make a service which takes no arguments. Hence we could have defined our ponyService.getBestPony like the following:

angular.module("lift.pony")
  .factory("ponyService", jsObjFactory()
    .jsonCall("getBestPony", {
      // Return the best pony (server-side)
      try {
        Full(BestPony)
      } catch {
        case e:Exception => Failure("No Pony!")
      }
    })
  )

Or we can accept a String...

angular.module("lift.pony")
  .factory("ponyService", jsObjFactory()
    .jsonCall("getPonyByName", (name:String) => {
      // Return the matching pony
      try {
        Full(BestPony)
      } catch {
        case e:Exception => Failure("No Pony!")
      }
    })
  )

Finally, perhaps most importantly, we expect a case class to be sent to the server. Note that the case class must extend NgModel for this to work. (Read more about models here)

case class Pony (name:String, img:URL) extends NgModel

angular.module("lift.pony")
  .factory("ponyService", jsObjFactory()
    .jsonCall("setBestPony", (pony:Pony) => {
      // Nothing to return
      Empty
    })
  )

Multiple function calls

All of the above functions can be part of the same service...

angular.module("lift.pony")
  .factory("ponyService", jsObjFactory()
    .jsonCall("getBestPony", {
      // Return the best pony (server-side)
      Full(BestPony)
    })

    .jsonCall("getPonyByName", (name:String) => {
      // Return the matching pony
      Full(MyPony)

    .jsonCall("setBestPony", (pony:Pony) => {
      // Nothing to return
      Empty
    })
  )

Futures

All of the examples thus far have assumed the value can be calculated quickly without expensive blocking or asynchronous calls. Since it is quite common to perform expensive operations or call APIs which return a Future[T], it is important that lift-ng likewise supports returning a future.

The same signatures for jsonCall are supported for futures:

angular.module("lift.pony")
  .factory("ponyService", jsObjFactory()
    .future("getBestPony", {
      // Create the future
      val f = new LAFuture[Box[Pony]]()
      // Do something to get the result
      futurePonyGetter(f)
      // Return the future that will contain a Pony
      f
    })

    .future("getPonyByName", (name:String) => {
      // Return a future containing the matching pony
      futurePonyGetter(name)

    .future("setBestPony", (pony:Pony) => {
      // Nothing to return
      val f = new LAFuture[Box[Pony]]()
      f.satisfy(Empty)
      f
    })
  )

In addition to supporting net.liftweb.actor.LAFuture, we also provide support for scala.concurrent.Future via conversions. See this section for details

Because the underlying Lift library does not currently support returning futures for AJAX calls (as of 2.5.1/2.6), we had to circumvent this limitation by utilizing comet. As a result, if you want to utilize futures in your angular app, we must be able to locate your app in the DOM. By default, we look for any elements containing the ng-app attribute. This can be overridden in the Angular.init() call via the appSelector property. This allows us to hook in to your app via comet and send messages asynchronously back to the lift-proxy service.

Testing

Testing services provided by lift-ng with Jasmine (etc) can be accomplished in the same manner as you would test any Angular service.

describe("pony", function(){
  // Service mock
  var ponyService = {};

  // Handle to the rootScope
  var rootScope = {};

  // Handle to the scope
  var scope = {};

  // Set up the pony module
  beforeEach(function(){module('pony');});

  // Mock out the service
  beforeEach(function() {
    angular.mock.module(function($provide) {
      $provide.value('lift.pony', ponyService);
    });
  });

  // Build the mock with a $q promise
  beforeEach(inject(function($q) {
    ponyService.defer = $q.defer();
    ponyService.getBestPony = function() {
      return this.defer.promise;
    };
  }));

  // Create a controller for each test
  beforeEach(inject(function($rootScope, $controller) {
    rootScope = $rootScope;
    scope = $rootScope.$new();
    $controller('PonyCtrl', {
      $scope: scope,
      ponyService: ponyService
    });
  }));

  // Write a test
  it('should call the service when onClick is called', function() {
    // Before onClick, the pony will be undefined.
    expect(scope.pony).toBeUndefined();

    // Provide a pony to be returned
    var pony = {
      name: 'Doug',
      img: 'doug.jpg'
    };
    ponyService.defer.resolve(pony);

    // Simulate the click
    scope.onClick();

    // This call lets the $q callback happen
    rootScope.$digest();

    // Expect that pony has now been set.
    expect(scope.pony).toEqual(pony);
  });
});

Under the Services' hood

Unlike most AngularJS RESTful http backends, you have no further work to do to secure your application. Rather than a fixed named endpoint, lift-ng dynamically creates an http endpoint for each service per page load. The name given to the end points is a securely-randomized number that is difficult to predict for an attacker attempting to utilize cross-site scripting techniques for instance.

In regards to testing the server-side code, we recommend implementing your service logic in a standalone module which handles all of the complex business logic. Then utilize lift-ng to merely expose those services to your angular app. This way your business logic is decoupled from lift-ng and easily testable.

Non-AJAX

Sometimes the value you want to provide in a service is known at page load time and should not require a round trip back to the server. Typical examples of this are configuration settings, session values, etc. To provide a value at page load time, just use JsonObjFactory's string, anyVal, or json methods.

angular.module("StaticServices")
  .factory("staticService", jsObjFactory()
    .string("string", "FromServer1")
    .anyVal("integer", 42)
    .json("obj", StringInt("FromServer2", 88))

  )

The above produces a simple service equivalent to the following JavaScript

angular.module("StaticServices",["lift-ng"])
  .factory("staticService", function(liftProxy) { return {
    string:  function() {return "FromServer1"},
    integer: function() {return "42"},
    obj:     function() {return {str:"FromServer2",num:88}}
  }});

Server-Initiated Events

Now we can take a look at how to utilize Lift's comet support to asynchronously send angular updates from the server

First you should write a new class which extends the AngularActor trait, which is a sub-trait of Lift's CometActor. Thus you can do anything you can normally with a CometActor, as well as get access the $scope where the actor is defined in the DOM and the $rootScope of the angular application. Currently we support $emit, $broadcast, and assignment of arbitrary fields on the given scope object.

class CometExample extends AngularActor {
  override def lowPriority = {
    case ("emit", msg:String) => rootScope.emit("emit-message", msg)
    case ("emit", obj:AnyRef) => rootScope.emit("emit-object",  obj)
    
    case ("broadcast", msg:String) => scope.broadcast("emit-message", msg)
    case ("broadcast", obj:AnyRef) => scope.broadcast("emit-object",  obj)

    case ("assign", msg:String) => rootScope.assign("my.str.field", msg)
    case ("assign", obj:AnyRef) => scope.assign("my.obj.field", obj)
  }
}

Now add the comet actor into your HTML DOM within the scope you wish to belong to within the ng-application.

<div ng-app="ExampleApp">
  <div data-lift="comet?type=CometExample"></div>
  <!-- other stuff -->
</div>

Then do whatever you need in your angular application to listen for events, watch for changes, etc.

angular.module('ExampleApp', ['lift-ng'])
.controller('ExampleController', ['$rootScope', '$scope', function($rootScope, $scope) {
  $rootScope.$on('emit-message', function(e, msg) {
    $scope.emitMessage = msg;
  });
  $rootScope.$on('emit-object', function(e, obj) {
    $scope.emitObject = obj;
  });
  $scope.$on('broadcast-message', function(e, msg) {
    $scope.broadcastMessage = msg;
  });
  $scope.$on('broadcast-object', function(e, obj) {
    $scope.broadcastObject = obj;
  });
  $rootScope.$watch('my.str.field', function(e, msg) {
    // ...
  });
  $scope.$watch('my.obj.field', function(e, obj) {
    // ...
  });
}]);

Note that messages sent prior to a page bootstrapping the Angular application will be queued up and released in order once the application is ready. The retry interval defaults to 100 milliseconds and can be configured in your Lift application's props files with the net.liftmodules.ng.AngularActor.retryInterval Int property.

Client-Server Model Binding

Just as Angular provides declarative 2-way binding between the model and view with automatic synchronization, lift-ng features binding of a model between the client and server. To take advantage of this feature, first create a model case class which extends NgModel. (Read more about models here)

case class Message(msg:String) extends NgModel

Then create binder in your comet package which extends NgModelBinder or SimpleNgModelBinder. (The latter is a conveniently-constructed form of the former) By default, your binder will be scoped per-request/per-page-load. Mix in SessionScope to cause your binder's state to persist among each page load of a user's session. You must specify the direction you want to bind data by mixing in BindingToClient, BindingToServer, or both to achieve two-way synchronization. The following example establishes a two-way binding existing in the session scope (identical to the original 0.5.0 release which featured BindingActor)

package org.myorg.comet

class MessageBinder extends SimpleNgModelBinder[Message] (
  "theMessage",       /* Name of the $scope variable to bind to */
  Message("initial"), /* Initial value for theMessage when the session is initialized */
  { m:Message =>      /* Called each time a client change is received */
    m
  },
  1000                /* Milliseconds for client-sync delay (see Optimizations below) */
) with BindingToClient with BindingToServer with SessionScope

Once defined, add the binder to the scope you want this model to exist in.

<div ng-app="MyLiftNgApp">
  <div ng-controller="MyController" data-lift="Angular.bind?type=MessageBinder">
    <input type="text" ng-bind="theMessage.msg"/>
    <div>{{theMessage.msg}}</div>
  </div>
</div>

If you have multiple binds, you can specify them in types via a comma-delimited list:

<div ng-app="MyLiftNgApp">
  <div ng-controller="MyMultipleBinds" data-lift="Angular.bind?types=Binder1,Binder2">
    <!-- Other stuff... -->
  </div>
</div>

If you mixed in BindingToServer, you will get state updates for the client (or clients if using SessionScope) via onClientUpdate:

class MyBinder extends NgModelBinder[MyModel] with BindingToServer {
  override val onClientUpdate = { fromClient =>
    println(s"We go a model update from the user! $fromClient")
  }

  // ...
}

Since watching scope variables on the client can produce a flood of changes (e.g. each character entered in a text box will generate a change event), changes are queued up and sent after no more changes are detected for 1000 millis. The fourth argument to the SimpleNgModelBinder constructor or an override of clientSendDelay in NgModelBinder allows you to tweak this delay to your liking.

If you mixed in BindingToClient, you can update your clients (if using SessionScope) by sending the binder a message with the model:

val newMessage = Message("Updated!")

// Find the binder
for {
  session <- S.session
  binder <- session.findComet("MessageBinder")
} { binder ! newMessage } // Send the new model

Optimizations

Mix in the BindingOptimizations trait to reduce the network overhead. Changes to a bound model on the server will be communicated to the client by sending only a diff.

Currently the client sends the entire model back to the server on change even when mixing BindingOptimizations. We hope to one day support sending only the diff just like we do when sending from the server.

Arrays are not correctly supported yet. A client-side change to an array will append to the array on the server rather than replacing the respective values based on the index.

Removing stuff from a model on the server does not transmit to the client yet. Only changes or additions to the model will be synced up to the client.

Memory consumption

Depending on the mixins utilized, you will store up more memory on the server when using an NgModelBinder. If utilizing BindingOptimizations or SessionScope, we must maintain the last known state of your model. This allows us to (1) compare to any model changes provided and transmit only the diff from the server and (2) render new pages with the current state.

Model objects

Any case class can be used as a model in lift-ng. However, models which are sent to the server from the client must mix in the NgModel trait. While models serialized to the client don't need this flag trait, but it is a good practice to include it to avoid errors as your application changes over time. Note that objects contained in an NgModel instance also do not need this flag trait either.

Embedded Futures

In addition to data fields which serialize naturally to their equivalent JSON representation, any model can contain fields that are futures of type net.liftweb.actor.LAFuture[Box[T]] for an arbitrary T <: Any. Such fields will be mapped to the client representation of the model as a promise from the $q angular service. The future will be plumbed to the client-side promise automatically, regardless of where the future appears in the model object graph.

For instance, given this Scala case class model:

case class MyModel (
  fastValue:String,
  slowValue:LAFuture[Box[String]]
) extends NgModel

You will receive the following object on the client:

var myModel = // However you get it from lift-ng
myModel.fastValue // A string
myModel.slowValue // A promise

myModel.slowValue.then(function(value){
  console.log('The value is '+value)
});

Once the LAFuture is satisfied, the result will be pushed up via comet to resolve/reject the promise according to the Box value. The Box value is mapped with the same logic as with client-initiated service calls. See Mapping Box to Promise.

Embedded futures work for responses to client-initiated service calls, server-initiated events, and client-server model binding. The only call which does not support embedded futures is non-AJAX service calls via jsObjFactory().json where the intent is to provide values known at page load time.

In addition to Lift's LAFuture, Scala's scala.concurrent.Future can also be embedded. The conversion details are documented below.

scala.concurrent.Future

As of Scala 2.10, the language library includes support for futures via the scala.concurrent.Future. Builds of lift-ng for Scala 2.10+ provide support for this implementation of Future as well. The object net.liftmodules.ng.FutureConversions provides two implicit conversions. One will convert a Future[T] into an LAFuture[Box[T]] implicitly. The other decorates Future[T] with a function named la to force the conversion as needed. See below for a full example.

import net.liftweb.util.Schedule
import net.liftweb.util.Helpers._
import net.liftmodules.ng.FutureConversions._
import scala.concurrent. { Promise, Future }
import scala.concurrent.ExecutionContext.Implicits.global
import scala.util.Try

// Create a Scala Promise first.
val p = Promise[String]()

// Satisfy the promise with a String a second from now.
Schedule.schedule(() => p.complete(Try("ScalaFuture")), 1 second)

// Implicit conversion to LAFuture
val laf1:LAFuture[Box[String]] = p.future

// Slightly less implicit conversion to LAFuture
val laf2 = p.future.la

The mapping of Future[T] to LAFuture[Box[T]] works as follows:

• A satisfied Future[T] with value t will be mapped to an LAFuture[Box[T]] satisfied with Full(t).
• A failed Future[T] with exception e will be mapped to an LAFuture[Box[T]] satisfied with Failure(e.getMessage, Full(e), None)

The Box[T] is then wired up to a $q promise on the client as outlined here. The net result is a completed Future[T] maps to a resolved promise, and a failed Future[T] maps to a rejected promise.

i18n Internationalization

If your app doesn't require sophisticated internationalization capabilities (i.e., Java resource bundles will suffice), then you can inject your resource bundles as a service into your app.

Given a resource bundle named bundleName.properties:

hello=Howdy!
goodbye=Goodbye, {0}!

Add it as a service available to your Angular app with this HTML:

<script id="my-i18n_js"  data-lift="i18n?name=bundleName"></script>

Your bundle is made available via the i18n module with service/factory name coinciding with the bundle name. In this example, the object will have a string field named hello and a function named goodbye:

angular.module('ExampleApp', ['i18n'])
.controller('ExampleController', ['$scope', 'bundleName', function($scope, i18n) {
  $scope.hello = i18n.hello;
  $scope.goodbye = i18n.goodbye($scope.username);
}]);

You may also specify multiple bundle names. Here we include the default Lift bundle:

<script id="my-i18n_js"  data-lift="i18n?names=bundleName,lift"></script>

Each bundle is another service available in the i18n bundle. Also notice in this example we show keys which aren't valid JavaScript identifiers are also available.

angular.module('ExampleApp', ['i18n'])
.controller('ExampleController',
  ['$scope', 'bundleName', 'lift', function($scope, bundle, lift) {
    $scope.hello = bundle.hello;
    $scope.goodbye = bundle.goodbye($scope.username);
    $scope.lostPasswd = lift["lost.password"];
}]);

For more details about this resource bundle object, see j2js-i18n.

$rootScope Events

NOT SUPPORTED IN LIFT 3.x AT THIS TIME

We have a few $rootScope events to keep your application informed of the browser's ability to communicate with the server. Whenever we receive a non-200 response from the backend server, we will issue a net_liftmodules_ng.serverCommError event on $rootScope. This event is raised on every failure, including retries which are otherwise transparent to the application. Included with the event is [1] the number of consecutive errors encountered, [2] the communication type that failed (either "ajax" or "comet"), and [3] the request object that failed (if "ajax"). This allows your client application to alert the user that communication to the server is struggling.

Once a the server has been successfully contacted after a communication error, we will issue a net_liftmodules_ng.serverCommErrorClear event on $rootScope. Included with this event is the communication type which succeeded (either "ajax" or "comet").

Note that an http error when contacting a Lift server doesn't necessarily imply that network communication is failing. For instance, if a server-side ajax function raises an Exception, Lift will respond with a 500. But with lift-ng in particular, any server-side ajax functions which you register with a jsObjFactory() are invoked in a try/catch pair to convert any exceptions into a failed Promise. Hence you can regard any net_liftmodules_ng.serverCommError events as a good indicator that something outside the control of your application is not going well.

Example Usage

angular.module("MyServerCommAwareModule", ["lift-ng"])
.run(["$rootScope", "$window", function($rootScope, $window){
  $rootScope.$on("net_liftmodules_ng.serverCommError", function(e, count, which, request) {
    console.log("Server communication error due to "+which+". Current count: "+count);
    if(count > 10)
      $window.alert("Hey, things aren't looking good!");
  });
  $rootScope.$on("net_liftmodules_ng.serverCommErrorClear", function(e, which) {
    console.log("Server communication errors cleared after a "+which+" success!");
  });
}]);

The Angular snippet

As mentioned earlier in this README, you need the Angular snippet on each page for lift-ng to function. This snippet expands into several script tags for gluing Angular to Lift, including angular.js itself from a webjar if available on your classpath and configured in Boot. In development mode, this will cause your pages to load non-minified versions of angularjs modules. In all other modes, your pages will request the minified versions.

<script data-lift="Angular"></script>

You can optionally set the additional-angularjs-modules parameter to override the list of angularjs modules you configured in Boot.

<script data-lift="Angular?additional-angularjs-modules=animate,cookies,loader,route"></script>

You can optionally set the min parameter to force the minified js file to be served with on, yes, or true, OR to force the full js file to be served with off, no, or false. Default behavior is to serve the minified version in all modes except RunModes.Development.

<script data-lift="Angular?min=off"></script>

Scaladocs

The latest version of scaladocs are hosted thanks to cloudbees continuous integration services. There should not be any differences among the supported versions of Scala. Nonetheless all are listed here for good measure.

• Scala 2.10
• Scala 2.9.2
• Scala 2.9.1-1
• Scala 2.9.1

Community/Support

Need help? Hit us up on the Lift Google group. We'd love to help you out and hear about what you're building.

Contributing

As with any open source project, contributions are greatly appreciated. If you find an issue or have a feature idea, we'd love to know about it! Any of the following will help this effort tremendously.

1. Issue a Pull Request with the fix/enhancement and unit tests to validate the changes. OR
2. Issue a Pull Request with failing tests in the test-project to show what needs to be changed OR
3. At a minimum, open an issue to let us know about what you've discovered.

Pull Requests

Below is the recommended procedure for git:

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push the branch (git push origin my-new-feature)
5. Create new Pull Request

Please include as much as you are able, such as tests, documentation, updates to this README, etc.

Testing

Part of contributing your changes will involve testing. The test-project sub-directory contains and independent sbt project for thoroughly testing the lift-ng module via selenium. At a minimum, we ask that you run the tests with your changes to ensure nothing gets inadvertently broken. If possible, include tests which validate your fix/enhancement in any Pull Requests.

Wish list

Here are things we would like in this library. It's not a road map, but should at least give an idea of where we plan to explore soon.

• Add an onRender function to AngularActor to allow performing a scope operation when the page is rendered.
• Cleanup JsObjFactory method names (see New interface for JsObjFactory below).
• Support server comet pushes to client via services.
• Remove need to wrap angular.module in renderIfNotAlreadyDefined().
• Resolve the RequestVar was set but not read warning (see Issue #11).
• Correctly support client-side changes to models containing arrays when mixing BindingOptimizations into an NgModelBinder.
• Support removing fields in models bound with an NgModelBinder with BindingOptimizations mixed in.
• Retain diffs in NgModelBinder. Allow server to reject client-side changes.
• Support Lift's Record with NgModel.
• Support dynamically-loaded templates for routing frameworks. (See Issue 7)
• Support handling parameters of type json.JValue.
• Support returning values of type JsExp.
• Provide a means of utilizing the third notify function of promises to send progress updates to the client.
• Initial value/first resolve value for services. The reason for providing a first value will allow the page load to deliver the values rather than require an extra round trip.

New interface for JsObjFactory

As of 0.7.0, lift-ng is in a transition phase for cleaning up the JsObjFactory interface. The end goal is to express the sematics clearly in the name and have low-noise syntax. The current plan is to have two methods on JsObjFactory which express when the values are evaluated: vals() and defs(). Just like with the Scala keywords val and def, these names suggest that the values will be evaluated when assigned and on each call, respectively. defs will take a variable list of function assignments to effectively deprecate jsonCall and future. vals will take a variable list of assignments to effectively deprecate string, anyVal, and json. Macros will be used to make the syntax clean. For example, the following will be a valid Angular module:

angular.module("MyServices")
  .factory("MyService", jsObjFactory()
    .defs(
      fn1 = (arg:String) => Service call arg,
      fn2 = (arg:Model) =>  Service call arg
    )
    .vals(
      constant1 = "Evaluated at page-load!",
      constant2 = 42
    )
  )

Part of the transition period is the introduction of six new methods: defAny, defStringToAny, defModelToAny, defFutureAny, defStringToFutureAny, and defModelToFutureAny. These are replacing jsonCall and future. The purpose is to avoid having over-loaded method signatures which cause problems with defaults, inference, etc. The macro described above will rewrite defs into a chain of these six functions. These functions have been introduced ahead of the macro for the sake of allowing the implicit JSON Formats parameter to be provided (see JSON Serialization).

Change log

• 0.10.2: Updated the JsObjFactory implementation to cleanly serialize/deserialize with the Kryo serialization library.
• 0.10.1: Minor internal update to update lift-ng angular services to explicitly annotate dependencies.
• See Angular Strict DI for more information.
• 0.10.0: Adds failureHandler: Failure => Reject to the init() function.
• 0.9.6: Indirect bug fix for i18n-internationalization by bumping j2js-i18n dependency. Quotes in parameterized strings are now correctly escaped.
• 0.9.5: Minor bug fix to guarantee server-side exceptions form valid JSON responses to the client.
• 0.9.4: This release contains exactly the same code as 0.9.3, thanks to midnight piloting errors.
• 0.9.3: Updates for compatibility with latest Lift 3.0 release candidate (RC3 in particular). Lift-json call has been updated per Lift framework PR 1766. A recompile of the plugin against Lift 3.0-RC3 also resolved some bytecode-level issues. First release compiled for Lift 3.1 (3.1.0-M2 in particular).
• 0.9.2: Corrects a bug where the i18n module would not load on pages which reside in a subdirectory of webapp.
• 0.9.1: Corrects a bug where i18n modules with special characters were not properly encoded in the URL. This is a common case as resource bundles can be organized in a subdirectory of src/main/resources
• 0.9.0: See Release Notes for details. Ajax calls now use Lift's mechanism rather than angular's $http service allowing retries, timeouts, etc to be configurable via LiftRules. Added retryAjaxInOrder to init() which when enabled guarantees your ajax requests will arrive on the server in order, even if an attempt fails NOT SUPPORTED IN LIFT 3.x AT THIS TIME. Added net_liftmodules_ng.serverCommError and net_liftmodules_ng.serverCommErrorClear events on $rootScope NOT SUPPORTED IN LIFT 3.x AT THIS TIME. Exceptions thrown by your ajax functions are caught and the exception's message is returned to the client in a rejected promise.
• 0.8.0: See Release Notes for details. Added Webjars integration to inject angularjs javascript files into your pages.
• 0.7.0: See Release Notes for details. POSSIBLE BREAKING CHANGE Resolved Issue 12: Calling defModelToAny, defModelToFutureAny, or jsonCall with a function that takes neither a String or NgModel will fail to compile. Functions which serialize/deserialize JSON now take an implicit net.liftweb.json.Formats. Resolved Issue 10: Futures can now be embedded in models of an NgModelBinder Optimized LAFuture/Future serialization.
• 0.6.4: Corrects a race condition where an embedded Future or LAFuture which happened to resolve during JSON serialization would never arrive on the client. Added a developer WARN server console message for when the client sends invalid json. The message asks the developer if they remembered to extend NgModel which is a super common root cause of the problem, and very frustrating to diagnose.
• 0.6.3: Fixes a client-side error that occurs when a model returned from a service contains a null field. This bug was likely introduced in 0.6.0.
• 0.6.2: Fixes for bugs exposed by placing two NgModelBinders in two different controllers on one page.
• 0.6.1: Added support for scala.concurrent.Future.
• 0.6.0: Introduction of embedded futures. BREAKING CHANGE: All of your angular modules now must directly or indirectly depend on the lift-ng module.
• 0.5.6: Bug Fix: Strings pushed to the client are now properly escaped. Prior to this fix, a string containing illegal characters such as a newline would be silently discarded.
• 0.5.5: Further decomposed NgModelBinder, separating the transmission optimizations into the BindingOptimizations mixin. With this update, an NgModelBinder should work for all cases by default.
• 0.5.4: BREAKING CHANGE: Renamed BindingActor to NgModelBinder. Decomposed NgModelBinder so it is possible to specify:
  • BindingDirection by mixing in BindingToClient, BindingToServer, or both for 2-way binding
  • BindingScope which defaults to per-request (i.e. per page load) and can be scoped to the session like the original BindingActor behavior by mixing in SessionScope
• 0.5.3: Fixed handling of NgModelBinder initial values. Fixed usage of CometListener with a 2-way session-scoped NgModelBinder by reversing the order in which the named/unnamed comet actors are rendered. Fixed support for Lift 3.0-SNAPSHOT. Enhanced automated testing to cover 2.10/2.5, 2.10/2.6, 2.11/2.6, and 2.11/3.0 Scala/Lift versions.
• 0.5.2: Resolved Issue #5, where the deployment context path appeared twice in the path to the liftproxy.js resource. Dropped support for Lift 3.0 compiled against Scala 2.10.
• 0.5.1: Corrected a bug exposed by 2-way binding that our early-arrival mechanism to not work if angular.js files are specified at the end of the HTML. Made it possible to add NgModelBinders in the HTML templates without introducing an extra element. Thanks to Antonio for the suggestion!
• 0.5.0: Introduction of 2-way client/server NgModel binding. Added support for Scala 2.11 against Lift editions 2.6 and 3.0.
• 0.4.7: Updated to work on pages that are in subdirectories. See Pull Request #4. Thank you voetha for the contribution!
• 0.4.6: Minor correction to resolution for Issue #1 to correctly allow messages to begin dequeuing without waiting for a new message. Added includeJsScript parameter to Angular.init() to give developers the ability to download the liftproxy.js their own way, such as via head.js. Updated closure compiler.
• 0.4.5: Now queues and releases async (AngularActor) messages arriving prior to Angular bootstrapping, resolving Issue #1.
• 0.4.4: Fixed the last version, which would serve the same i18n locale resource for every requested locale.
• 0.4.3: Enhanced i18n service to be served restfully, allowing the browser to cache the service if it has not changed. Dropped 2.9.1-1 support. Began compiling 2.10 with 2.10.4.
• 0.4.2: Reverted a change made in 0.4.0 which allows more flexibility in the placement of angular services in the DOM, fixing part 2 of Issue #2
• 0.4.1: Now works for web apps running in a non-root context, fixing Issue #2.
• 0.4.0: Now only requires Angular snippet in your template(s).
• 0.3.1: Added i18n service.
• 0.3.0: Implemented support for a factory/service to return an LAFuture[Box[T]]
• 0.2.3: Implemented string, anyVal, and json on JsonObjFactory to allow providing values which are known at page load time and do not otherwise change.
• 0.2.2: Implemented AngularActor.assign for assigning scope variables. Failure(msg) message is sent to the client for $q.reject. Changed interpretation of Empty to mean Resolve rather than Reject.
• 0.2.1: Implemented scope.broadcast and scope.emit for AngularActor
• 0.2.0: Introduction of AngularActor featuring rootScope.broadcast and rootScope.emit as the first comet-backed features
• 0.1.1: First working release
• 0.1: First release featuring AJAX services invoked from the client

License

lift-ng is licensed under APL 2.0.

Copyright 2015 net.liftweb

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.