Javassist: create dynamic proxy to override methods of a class and record the method names as they are called

MethodReaderProxy.scala

package edu.urmc.lis.datawarehousequery.schema.fieldbuilder.javassist
import javassist.util.proxy.ProxyFactory
import javassist.util.proxy.MethodHandler
import java.lang.reflect.Method

class MethodReaderProxy[T: Manifest] {
  private var lastMethod: Option[Method] = None
  private var methodManifest: Option[Manifest[_]] = None
  private val clazz = manifest[T].erasure

  def getMethodName: Option[String] = lastMethod.map(_.getName()) //return name of method invoked
  def getMethodName[A: Manifest](method: (T) => A): String = {
    methodManifest = Some(manifest[A])
    method(proxy); //invoke method
    lastMethod.map(_.getName()).get //return name of method invoked
  }

  def getMethodReturnType: Option[String] = methodManifest map (_.toString()) //return type of method invoked
  def getMethodReturnType[A: Manifest](method: T => A) = {
    methodManifest = Some(manifest[A])
    method(proxy) //invoke method
    methodManifest.get.toString()

  }

  val proxy = {
    val factory = new ProxyFactory();
    factory.setSuperclass(clazz);
    factory.setHandler(new MethodHandler {
      @throws(classOf[Throwable])
      override def invoke(self: java.lang.Object, thisMethod: Method, proceed: Method, args: scala.Array[java.lang.Object]): java.lang.Object = {
        lastMethod = Some(thisMethod)

        def is[A: Manifest] = thisMethod.getReturnType() == manifest[A].erasure

        if (is[Int] || is[Short])
          0.asInstanceOf[AnyRef]
        else if (is[Double]) (0.0).asInstanceOf[AnyRef]
        else if (is[Option[_]]) None
        else if (is[Unit] || is[Void]) Unit
        else if (is[String]) ""
        else throw new Exception("Unhandled type: " + thisMethod.getReturnType().toString())
      }
    });
    val proxyClass: Class[T] = factory.createClass().asInstanceOf[Class[T]];

    proxyClass.newInstance();

  }
}

MethodReaderProxySpec.scala

package edu.urmc.lis.datawarehousequery.schema.fieldbuilder.javassist
import org.junit.runner.RunWith
import org.specs2.mutable.Specification
import org.specs2.runner.JUnitRunner
import akka.actor.Scope
import edu.urmc.lis.datawarehousequery.schema.fieldbuilder.FieldAttributeMapping
import edu.urmc.lis.datawarehousequery.schema.lab.Orders

@RunWith(classOf[JUnitRunner])
class MethodReaderProxySpec extends Specification {

  "MethodReaderProxy" should {

    "Be able to proxy a table, and print out the name then returnType of called methods" in {
      val fMap = new MethodReaderProxy[Orders]

      fMap.getMethodName(_.abnormal_low) mustEqual "abnormal_low"
      fMap.getMethodReturnType.get mustEqual "Int"

    }
    "Be able to proxy a table, and print out the returnType then name of called methods" in {
      val fMap = new MethodReaderProxy[Orders]

      fMap.getMethodReturnType(_.aotests_24) mustEqual "scala.Option[java.lang.String]"
      fMap.getMethodName.get mustEqual "aotests_24"
    }

  }

}