CODEWITHSUNDEEP
javascalareflection
Harsh Gupta
Harsh Gupta

Reputation: 331

How to get TypeTag from java.lang.Class

I have a requirement where I need to send from java or scala class a 3rd party class name to an API which I am writing in scala . From that (3rd party) class name I have to instantiate its object (which might have a parameterized constructor as well) and call its corresponding methods . I made attempts but I am not very well clear with the complete reflection working so it looks like this for now:

External (java/scala) class accessing the API :

class AnyRandomClass{

MyAPI api = new API();
api.getThirPartyObject(ThirdPartyClassName);
}

Here is the attempt to write the scala API :

package mypckg

import scala.reflect.runtime._
import scala.reflect.runtime.universe._

class MyAPI{
def getThirdPartyObject ={
   val u = universe
   val m = u.runtimeMirror(getClass.getClassLoader)
   //throws error : type staticClass is not a member of mypckg.MyAPI.u.Mirror
   m.runtimeClass(typeOf[m.staticClass(clazz.getName).selfType].typeSymbol.asClass)
}

}

Please help me understand where am I going wrong here , also whats the correct and better way to do it .

Upvotes: 2

Views: 1141

Answers (1)

Alexey Romanov
Alexey Romanov

Reputation: 170713

I have a requirement where I need to send from java or scala class a 3rd party class name to an API which I am writing in scala . From that (3rd party) class name I have to instantiate its object (which might have a parameterized constructor as well) and call its corresponding methods

You don't need a TypeTag for this. Just using Java reflection:

val constructors = clazz.getConstructors 
// see also getConstructor, getDeclaredConstructors, and getDeclaredConstructor
val constructor = // select the constructor you need
constructor.newInstance(parameters)
// etc

If you do need to use Scala reflection, ClassTag should be enough and trivial to get:

ClassTag(clazz)

Upvotes: 1

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