Akka兒童演員給班級演員例外

Question

我的akka​​ java項目使用play framework來實現rubine算法時遇到問題，我想與社區分享以尋求解決方案。

該項目包含一個創建子演員的akka​​主演員。 然后，子角色會初始化一個執行某些任務的java類。 該任務的數據由使用websocket和json對象的Web界面提供。 json對象包含一個double數據類型。 播放框架應用程序類從Web界面獲取數據，並將其傳遞給主actor。 然后，主演員創建一個子演員，並將數據傳遞給該子演員。下面是代碼片段。 相關章節已公開

這來自應用程序類：

public class Application extends Controller {   
static ActorRef masterActor;
RubineActor rubineactor;

public static Result index() {        
return ok(index.render(null)); }

public static WebSocket<JsonNode> sockHandler() {     
return new WebSocket<JsonNode>() {
// called when the websocket is established
public void onReady(final WebSocket.In<JsonNode> in, final WebSocket.Out<JsonNode> out) { 

try{ RubineActor.connectMaster(in, out); }  

catch(Exception e){e.printStackTrace();}                        
      }  }; } }

這是來自男主角：

public class RubineActor extends UntypedActor {         
static ObjectMapper mapper;       
Map<String,ArrayList<Double>> jsonMap;          
LoggingAdapter log = Logging.getLogger(getContext().system(), this);        
ActorRef childActor = getContext().actorOf(new Props(ChildActor.class), "childactor");
static ActorRef masterActor = Akka.system().actorOf(new Props(RubineActor.class));    

public static void connectMaster (final WebSocket.In<JsonNode> in, 
final WebSocket.Out<JsonNode> out)
{   in.onMessage(new Callback<JsonNode>() {
public void invoke(JsonNode event) throws JsonParseException, JsonMappingException,  
IOException {    

ObjectMapper mapper = new ObjectMapper();                 
@SuppressWarnings("unchecked")
Map<String,ArrayList<Double>> jsonMap = mapper.readValue(event, Map.class);

masterActor.tell(new Coordinates(jsonMap));                                         
("timeArray").toString();  }    });   }

@Override
public void onReceive(Object message) throws Exception {        
if(message instanceof Coordinates)

{Coordinates msg = (Coordinates) message;
childActor.tell(msg); } 
else { unhandled(message);}  }

public static class Coordinates {                                                   
Map <String,ArrayList<Double>> jsonMap = null;              
public Coordinates (Map <String,ArrayList<Double>> jsonMap ) {              
super();
this.jsonMap = jsonMap;  }  }}
this is from the child actor
public class ChildActor extends UntypedActor {                  
public ChildActor (){}

@Override
public void onReceive(Object msg) throws Exception  

if(msg instanceof Coordinates) {
Coordinates cood = (Coordinates) msg;
new Gesture(cood.jsonMap);
    }
else { unhandled(msg);} }}

這是來自普通的java類：

Map<String, ArrayList<Double>> jsonMap ;
Map <String,ArrayList<Long>> jsonMap2 ;                             

public Gesture(){}        
public Gesture (Map<String, ArrayList<Double>> jsonMap)
{  this.jsonMap  = jsonMap;
npoints = jsonMap.size();
intial_Theta();  }

public void intial_Theta() {    

// this line produces a class cast exception error.the error is given below.
double  dx = jsonMap.get("x").get(2) - jsonMap.get("x").get(0);} 

這是錯誤消息：

[info] Compiling 4 Scala sources and 10 Java sources to C:\Users\FAISAL\workspac
e\Sketch_Server\target\scala-2.9.1\classes...
[info] play - Application started (Dev)
[info] play - Starting application default Akka system.
[ERROR] [08/07/2012 05:15:11.187] [application-akka.actor.default-dispatcher-3]
[akka://application/user/$a/childactor] java.lang.Integer cannot be cast to java
.lang.Double
java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Doub
le
        at model.Gesture.intial_Theta(Gesture.java:90)
        at model.Gesture.<init>(Gesture.java:74)
        at model.ChildActor.onReceive(ChildActor.java:19)
        at akka.actor.UntypedActor$$anonfun$receive$1.apply(UntypedActor.scala:1
54)
        at akka.actor.UntypedActor$$anonfun$receive$1.apply(UntypedActor.scala:1
53)
        at akka.actor.Actor$class.apply(Actor.scala:318)
        at akka.actor.UntypedActor.apply(UntypedActor.scala:93)
        at akka.actor.ActorCell.invoke(ActorCell.scala:626)
        at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:197)
        at akka.dispatch.Mailbox.run(Mailbox.scala:179)
        at akka.dispatch.ForkJoinExecutorConfigurator$MailboxExecutionTask.exec(
AbstractDispatcher.scala:516)
        at akka.jsr166y.ForkJoinTask.doExec(ForkJoinTask.java:259)
        at akka.jsr166y.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:975)
        at akka.jsr166y.ForkJoinPool.runWorker(ForkJoinPool.java:1479)
        at akka.jsr166y.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:104)

任何建議都會很高興。

Answer 1

在我看來，這與Akka或Play無關，只是在JSON數據中包含Integer值。

您可能希望不會以類型安全的語言發生這種情況，因為您已將變量聲明為ArrayList<Double> ，但這就是您的Java。 這是一個簡化的版本，可以重現您的問題：

import java.util.HashMap;
import java.util.Map;
import java.util.List;
import java.util.ArrayList;

public class x { 

    static void breakMap(Map x) { 
        ArrayList<Integer> l = new ArrayList<Integer>();
        l.add(new Integer(1));
        x.put("foo", l);
    };

    public static void main(String[] args) { 
        Map<String, ArrayList<Double>> x = new HashMap<String, ArrayList<Double> >();
        breakMap(x);

        ArrayList<Double> y = x.get("foo");
        Double z = y.get(0);

    }   
}

給

Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Double
        at x.main(x.java:20)