Question

I need to check that the type of the method first parameter is List<Class<? extends Exception>> or not. Can anybody suggested better solution than comparing it with a String?

Method m = Foo.class.getMethod("m1", List.class);
if (m.getGenericParameterTypes()[0].toString().equals("java.util.List<java.lang.Class<? extends java.lang.Exception>>")) {
  ...
}

I mean something like this:

List.class.isAssignableFrom((Class<?>)((ParameterizedType)m.getGenericParameterTypes()[0]).getRawType()));

This check that it is a list or not. But how I can check the Class<? extends Exception> part of the type?

Answer 1

Just tried the following, and it seems to work:

// package whatever.your.package.happens.to.be;

import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.WildcardType;
import java.util.List;

public class ReflectionTest {
  public static void main(String[] args) throws NoSuchMethodException, SecurityException {
    Method method = ReflectionTest.class.getMethod("method", List.class);
    ParameterizedType listType = (ParameterizedType)method.getGenericParameterTypes()[0];
    ParameterizedType classType = (ParameterizedType)listType.getActualTypeArguments()[0];
    WildcardType genericType = (WildcardType)classType.getActualTypeArguments()[0];
    Class<?> genericClass = (Class<?>)genericType.getUpperBounds()[0];

    boolean isException = Exception.class.isAssignableFrom(genericClass);
    // vvv Prints out "Is Class<? extends Exception>: true"
    System.out.println("Is Class<? extends Exception>: " + isException);

    boolean isRuntimeException = RuntimeException.class.isAssignableFrom(genericClass);
    // vvv Prints out "Is Class<? extends RuntimeException>: false"
    System.out.println("Is Class<? extends RuntimeException>: " + isRuntimeException);
  }

  public void method(List<Class<? extends Exception>> exceptionClasses) {
    // Do something with "exceptionClasses," I would imagine...
  }
}

Edit: Okay, for reals this time. I just now noticed that it was List<Class<? extends Exception>> and not List<? extends Exception>. So this (hopefully) final solution should actually match that case.