[xlang] Cross language serialize ActorHandle (#7134)

java/runtime/src/main/java/org/ray/runtime/actor/NativeRayActor.java

@@ -29,14 +29,11 @@ public abstract class NativeRayActor implements RayActor, Externalizable {
    */
   byte[] actorId;
 
-  private Language language;
-
-  NativeRayActor(long nativeCoreWorkerPointer, byte[] actorId, Language language) {
+  NativeRayActor(long nativeCoreWorkerPointer, byte[] actorId) {
     Preconditions.checkState(nativeCoreWorkerPointer != 0);
     Preconditions.checkState(!ActorId.fromBytes(actorId).isNil());
     this.nativeCoreWorkerPointer = nativeCoreWorkerPointer;
     this.actorId = actorId;
-    this.language = language;
   }
 
   /**
@@ -64,7 +61,7 @@ public abstract class NativeRayActor implements RayActor, Externalizable {
   }
 
   public Language getLanguage() {
-    return language;
+    return Language.forNumber(nativeGetLanguage(nativeCoreWorkerPointer, actorId));
   }
 
   public boolean isDirectCallActor() {
@@ -73,29 +70,55 @@ public abstract class NativeRayActor implements RayActor, Externalizable {
 
   @Override
   public void writeExternal(ObjectOutput out) throws IOException {
-    out.writeObject(nativeSerialize(nativeCoreWorkerPointer, actorId));
-    out.writeObject(language);
+    out.writeObject(toBytes());
   }
 
   @Override
   public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
+    nativeCoreWorkerPointer = getNativeCoreWorkerPointer();
+    actorId = nativeDeserialize(nativeCoreWorkerPointer, (byte[]) in.readObject());
+  }
+
+  /**
+   * Serialize this actor handle to bytes.
+   *
+   * @return  the bytes of the actor handle
+   */
+  public byte[] toBytes() {
+    return nativeSerialize(nativeCoreWorkerPointer, actorId);
+  }
+
+  /**
+   * Deserialize an actor handle from bytes.
+   *
+   * @return  the bytes of an actor handle
+   */
+  public static NativeRayActor fromBytes(byte[] bytes) {
+    long nativeCoreWorkerPointer = getNativeCoreWorkerPointer();
+    byte[] actorId = nativeDeserialize(nativeCoreWorkerPointer, bytes);
+    Language language = Language.forNumber(nativeGetLanguage(nativeCoreWorkerPointer, actorId));
+    Preconditions.checkNotNull(language);
+    return create(nativeCoreWorkerPointer, actorId, language);
+  }
+
+  private static long getNativeCoreWorkerPointer() {
     RayRuntime runtime = Ray.internal();
     if (runtime instanceof RayMultiWorkerNativeRuntime) {
       runtime = ((RayMultiWorkerNativeRuntime) runtime).getCurrentRuntime();
     }
     Preconditions.checkState(runtime instanceof RayNativeRuntime);
 
-    nativeCoreWorkerPointer = ((RayNativeRuntime) runtime).getNativeCoreWorkerPointer();
-    actorId = nativeDeserialize(nativeCoreWorkerPointer, (byte[]) in.readObject());
-    language = (Language) in.readObject();
+    return ((RayNativeRuntime) runtime).getNativeCoreWorkerPointer();
   }
 
-
   @Override
   protected void finalize() {
     // TODO(zhijunfu): do we need to free the ActorHandle in core worker?
   }
 
+  private static native int nativeGetLanguage(
+      long nativeCoreWorkerPointer, byte[] actorId);
+
   private static native boolean nativeIsDirectCallActor(
       long nativeCoreWorkerPointer, byte[] actorId);
 

java/runtime/src/main/java/org/ray/runtime/actor/NativeRayJavaActor.java

@@ -11,7 +11,7 @@ import org.ray.runtime.generated.Common.Language;
 public class NativeRayJavaActor extends NativeRayActor {
 
   NativeRayJavaActor(long nativeCoreWorkerPointer, byte[] actorId) {
-    super(nativeCoreWorkerPointer, actorId, Language.JAVA);
+    super(nativeCoreWorkerPointer, actorId);
   }
 
   /**

java/runtime/src/main/java/org/ray/runtime/actor/NativeRayPyActor.java

@@ -12,7 +12,7 @@ import org.ray.runtime.generated.Common.Language;
 public class NativeRayPyActor extends NativeRayActor implements RayPyActor {
 
   NativeRayPyActor(long nativeCoreWorkerPointer, byte[] actorId) {
-    super(nativeCoreWorkerPointer, actorId, Language.PYTHON);
+    super(nativeCoreWorkerPointer, actorId);
   }
 
   /**