How to read serialized object with a method taking generic type by Scala/Kryo? - scala

Question

Use Kryo to read serialized object is easy when I know the specific class type, but if I want to create a method that takes simple generic type, how to do it?
I have code that can not be compiled:
def load[T](path: String): T = {
val instantiator = new ScalaKryoInstantiator
instantiator.setRegistrationRequired(false)
val kryo = instantiator.newKryo()
val input = new Input(FileUtils.readFileToByteArray(new File(path)))
kryo.readObject[T](input, classOf[T])
}
The error I got is:
class type required but T found
kryo.readObject[T](input, classOf[T])
I know what the error means, but don't know the right way to fix it.
The code is modified by my original type-specific code:
def load(path: String): SomeClassType = {
val instantiator = new ScalaKryoInstantiator
instantiator.setRegistrationRequired(false)
val kryo = instantiator.newKryo()
val input = new Input(FileUtils.readFileToByteArray(new File(path)))
kryo.readObject(input, classOf[SomeClassType])
}

Answer 1

I've found the answer, the key is ClassTag:
def load[M: ClassTag](path: String)(implicit tag: ClassTag[M]): M = {
val instantiator = new ScalaKryoInstantiator
instantiator.setRegistrationRequired(false)
val kryo = instantiator.newKryo()
val input = new Input(FileUtils.readFileToByteArray(new File(path)))
kryo.readObject(input, tag.runtimeClass.asInstanceOf[Class[M]])
}
In some threads, the last line is:
kryo.readObject(input, tag.runtimeClass)
This doesn't work in my case, it has to be:
tag.runtimeClass.asInstanceOf[Class[M]]