Java example source code file (ClassRestrictions.java)

This example Java source code file (ClassRestrictions.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bar, bashful, baz, class, classloader, classrestrictions, error, failed, illegalargumentexception, interface, net, network, reflection, string, test, throwable, urlclassloader

The ClassRestrictions.java Java example source code

/*
 * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/* @test
 * @bug 4227192 8004928
 * @summary This is a test of the restrictions on the parameters that may
 * be passed to the Proxy.getProxyClass method.
 * @author Peter Jones
 *
 * @build ClassRestrictions
 * @run main ClassRestrictions
 */

import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.net.URLClassLoader;

public class ClassRestrictions {

    public interface Bar {
        int foo();
    }

    public interface Baz {
        long foo();
    }

    interface Bashful {
        void foo();
    }

    public static final String nonPublicIntrfaceName = "java.util.zip.ZipConstants";

    public static void main(String[] args) {

        System.err.println(
            "\nTest of restrictions on parameters to Proxy.getProxyClass\n");

        try {
            ClassLoader loader = ClassRestrictions.class.getClassLoader();
            Class<?>[] interfaces;
            Class<?> proxyClass;

            /*
             * All of the Class objects in the interfaces array must represent
             * interfaces, not classes or primitive types.
             */
            try {
                interfaces = new Class<?>[] { Object.class };
                proxyClass = Proxy.getProxyClass(loader, interfaces);
                throw new Error(
                    "proxy class created with java.lang.Object as interface");
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
                System.err.println();
                // assume exception is for intended failure
            }
            try {
                interfaces = new Class<?>[] { Integer.TYPE };
                proxyClass = Proxy.getProxyClass(loader, interfaces);
                throw new Error(
                    "proxy class created with int.class as interface");
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
                System.err.println();
                // assume exception is for intended failure
            }

            /*
             * No two elements in the interfaces array may refer to identical
             * Class objects.
             */
            try {
                interfaces = new Class<?>[] { Bar.class, Bar.class };
                proxyClass = Proxy.getProxyClass(loader, interfaces);
                throw new Error(
                    "proxy class created with repeated interfaces");
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
                System.err.println();
                // assume exception is for intended failure
            }

            /*
             * All of the interfaces types must be visible by name though the
             * specified class loader.
             */
            ClassLoader altLoader = new URLClassLoader(
                ((URLClassLoader) loader).getURLs(), null);
            Class altBarClass;
            altBarClass = Class.forName(Bar.class.getName(), false, altLoader);
            try {
                interfaces = new Class<?>[] { altBarClass };
                proxyClass = Proxy.getProxyClass(loader, interfaces);
                throw new Error(
                    "proxy class created with interface " +
                    "not visible to class loader");
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
                System.err.println();
                // assume exception is for intended failure
            }

            /*
             * All non-public interfaces must be in the same package.
             */
            Class<?> nonPublic1 = Bashful.class;
            Class<?> nonPublic2 = Class.forName(nonPublicIntrfaceName);
            if (Modifier.isPublic(nonPublic2.getModifiers())) {
                throw new Error(
                    "Interface " + nonPublicIntrfaceName +
                    " is public and need to be changed!");
            }
            try {
                interfaces = new Class<?>[] { nonPublic1, nonPublic2 };
                proxyClass = Proxy.getProxyClass(loader, interfaces);
                throw new Error(
                    "proxy class created with two non-public interfaces " +
                    "in different packages");
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
                System.err.println();
                // assume exception is for intended failure
            }

            /*
             * No two interfaces may each have a method with the same name and
             * parameter signature but different return type.
             */
            try {
                interfaces = new Class<?>[] { Bar.class, Baz.class };
                proxyClass = Proxy.getProxyClass(loader, interfaces);
                throw new Error(
                    "proxy class created with conflicting methods");
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
                System.err.println();
                // assume exception is for intended failure
            }

            /*
             * All components of this test have passed.
             */
            System.err.println("\nTEST PASSED");

        } catch (Throwable e) {
            System.err.println("\nTEST FAILED:");
            e.printStackTrace();
            throw new Error("TEST FAILED: ", e);
        }
    }
}