Accessing Package Scoped Methods In Java 9

compileAndRun.sh

package org.codefx.lab;

import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLStreamHandler;

public class GetURLStreamHandler {

	public static void main(String[] args) throws Exception {
		printDefaultPortForProtocol("http");
		printDefaultPortForProtocol("https");
	}

	private static void printDefaultPortForProtocol(String protocol) throws Exception {
		URLStreamHandler handler = getURLStreamHandler(protocol);
		int port = callGetDefaultPortOn(handler);
		System.out.printf(
				"default %s port: %d (delivered by %s; %s)%n",
				protocol,
				port,
				handler.getClass().getName(),
				determineJigsawPresenceByInstantiating(handler));
	}

	private static URLStreamHandler getURLStreamHandler(String protocol) throws Exception {
		Method method = URL.class.getDeclaredMethod("getURLStreamHandler", String.class);
		method.setAccessible(true);
		return (URLStreamHandler) method.invoke(null, protocol);
	}

	private static int callGetDefaultPortOn(URLStreamHandler handler) throws Exception {
		Method method = URLStreamHandler.class.getDeclaredMethod("getDefaultPort");
		method.setAccessible(true);
		return (int) method.invoke(handler);
	}

	private static String determineJigsawPresenceByInstantiating(URLStreamHandler handler) throws Exception {
		try {
			handler.getClass().newInstance();
			return "pre Jigsaw";
		} catch (IllegalAccessException ex) {
			return "Jigsaw";
		}
	}

}

GetURLStreamHandler.java

package org.codefx.lab;

import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLStreamHandler;

public class GetURLStreamHandler {

	public static void main(String[] args) throws Exception {
		printDefaultPortForProtocol("http");
		printDefaultPortForProtocol("https");
	}

	private static void printDefaultPortForProtocol(String protocol) throws Exception {
		URLStreamHandler handler = getURLStreamHandler(protocol);
		int port = callGetDefaultPortOn(handler);
		System.out.printf("default %s port: %d (delivered by %s)%n", protocol, port, handler.getClass().getName());
	}

	private static URLStreamHandler getURLStreamHandler(String protocol) throws Exception {
		Method method = URL.class.getDeclaredMethod("getURLStreamHandler", String.class);
		method.setAccessible(true);
		return (URLStreamHandler) method.invoke(null, protocol);
	}

	private static int callGetDefaultPortOn(URLStreamHandler handler) throws Exception {
		Method method = URLStreamHandler.class.getDeclaredMethod("getDefaultPort");
		method.setAccessible(true);
		return (int) method.invoke(handler);
	}

}

My experimentation for answering this question on Stack Overflow:

Is it possible to access package scoped methods by reflection in Java 9 with Jigsaw?

Execution

To execute it, a JDK 9 early access build (I tried it with build 113) should be installed and its bin folder be available under $JIGSAW_BIN. The class GetURLStreamHandler must be in src/org/codefx/lab, relative to compile.sh.

Result

Java 8

Compiling and running with Java 8 (e.g. with IDE) yields ...

default http port: 80 (delivered by sun.net.www.protocol.http.Handler; pre Jigsaw)
default https port: 443 (delivered by sun.net.www.protocol.https.Handler; pre Jigsaw)

... because the internal classes can be instantiated.

Java 9

Compiling and running with Java 9 (with the script) yields ...

default http port: 80 (delivered by sun.net.www.protocol.http.Handler; Jigsaw)
default https port: 443 (delivered by sun.net.www.protocol.https.Handler; Jigsaw)

... because the internal classes can not be instantiated, due to the module system.