播放2.1 Scala连锁多个期货和承诺

Question

I have an existing java class for processing data. How could I use the ObjectNode from first promise and so more processing in my Scala Async action?

public class JavaClass extends Controller {
  public static Promise<ObjectNode> intensiveComputation(String imageId) {
  }
}


def index = Action {
  val futureInt = scala.concurrent.Future { JavaClass.intensiveComputation() }
  Async {
    futureInt.map(promise => 
      var objJs = promise.GetObjectNodeFromPromise()
      (objJs \ Config.RESP_STATUS_PARAM).as[String] match {
        // I WANT TO READ ObjectNode from promise and do more works here
      }
      Ok(Json.toJson(Map("status" -> "ok")))
  }
}

EDIT 1

I tried with @hbf code, however, I got compiling error one this line.

[error]  found   : org.codehaus.jackson.node.ObjectNode => play.api.mvc.SimpleResult[play.api.libs.json.JsValue]
[error]  required: play.libs.F.Function[org.codehaus.jackson.node.ObjectNode,?]
[error]                 var result = futureObj map { objJs: ObjectNode =>

If I remove ObjectNode from objJs, I got this error.

[error]  missing parameter type
[error]                 var result = futureObj map { objJs =>

New Code

def index = Action {
  val futureInt = JavaClass.intensiveComputation()
  Async {
    var result = futureObj map { objJs: ObjectNode =>
      Ok(Json.toJson(Map("status" -> "ok")))
    }
    result
}

Answer 1

I assume you are following the Play documentation guide , right?

First of all, notice that Play is now (from version 2.1 on) using Scala futures and due to this, the nomenclature changed: your method intensiveComputation() returns a (Scala) Future<ObjectNode> (while in pre-2.1, this was called Promise<ObjectNode> ).

public class JavaClass extends Controller {
  public static Future<ObjectNode> intensiveComputation(String imageId) {
    /* ... */
  }
}

Also, note that in the Play documentation example , intensiveComputation() returns the value (ie, ObjectNode ) directly, while your version returns a future holding the value (ie, Future<ObjectNode> ).

Second, in your futureInt.map , the closure receives the value of the future and not the future itself. So try something like:

def index = Action {
  val futureInt = JavaClass.intensiveComputation() // I's already a future!
  Async {
    futureInt.map(objJs => // `objJs` is the result of `intensiveComputation`
      // Extract from `objJs` whatever you need ...
      // ... and make the `Ok` call here (and not outside)
      Ok(Json.toJson(Map("status" -> "ok")))
    )
  }
}