[Java] ObjectID::fromRandom sets proper flags (#5548)

java/api/src/main/java/org/ray/api/id/ObjectId.java

@@ -12,8 +12,6 @@ public class ObjectId extends BaseId implements Serializable {
 
   public static final int LENGTH = 20;
 
-  public static final ObjectId NIL = genNil();
-
   /**
    * Create an ObjectId from a ByteBuffer.
    */
@@ -21,21 +19,17 @@ public class ObjectId extends BaseId implements Serializable {
     return new ObjectId(byteBuffer2Bytes(bb));
   }
 
-  /**
-   * Generate a nil ObjectId.
-   */
-  private static ObjectId genNil() {
-    byte[] b = new byte[LENGTH];
-    Arrays.fill(b, (byte) 0xFF);
-    return new ObjectId(b);
-  }
-
   /**
    * Generate an ObjectId with random value.
    */
   public static ObjectId fromRandom() {
+    // This is tightly coupled with ObjectID definition in C++. If that changes,
+    // this must be changed as well.
+    // The following logic should be kept consistent with `ObjectID::FromRandom` in
+    // C++.
     byte[] b = new byte[LENGTH];
     new Random().nextBytes(b);
+    Arrays.fill(b, TaskId.LENGTH, LENGTH, (byte) 0);
     return new ObjectId(b);
   }
 

src/ray/core_worker/object_interface.cc

@@ -28,7 +28,7 @@ void GroupObjectIdsByStoreProvider(
     // to whether it's from direct actor call before we can choose memory store provider.
     if (object_id.IsReturnObject() &&
         object_id.GetTransportType() ==
-            static_cast<int>(TaskTransportType::DIRECT_ACTOR)) {
+            static_cast<uint8_t>(TaskTransportType::DIRECT_ACTOR)) {
       type = StoreProviderType::MEMORY;
     }
 
@@ -51,13 +51,16 @@ CoreWorkerObjectInterface::CoreWorkerObjectInterface(
 Status CoreWorkerObjectInterface::Put(const RayObject &object, ObjectID *object_id) {
   ObjectID put_id = ObjectID::ForPut(worker_context_.GetCurrentTaskID(),
                                      worker_context_.GetNextPutIndex(),
-                                     /*transport_type=*/0);
+                                     static_cast<uint8_t>(TaskTransportType::RAYLET));
   *object_id = put_id;
   return Put(object, put_id);
 }
 
 Status CoreWorkerObjectInterface::Put(const RayObject &object,
                                       const ObjectID &object_id) {
+  RAY_CHECK(object_id.GetTransportType() ==
+            static_cast<uint8_t>(TaskTransportType::RAYLET))
+      << "Invalid transport type flag in object ID: " << object_id.GetTransportType();
   return store_providers_[StoreProviderType::PLASMA]->Put(object, object_id);
 }