In-memory Jar Class Loader

Loader.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License") +  you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.openmeetings.screen.webstart;

import java.io.ByteArrayInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLConnection;
import java.net.URLStreamHandler;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.Provider;
import java.security.Security;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;

public class Loader {
	public static void main(String[] args) {
		try {
			final Map<String, byte[]> map = new HashMap<>();
			try (JarInputStream is = new JarInputStream(CoreScreenShare.class.getResourceAsStream("/lib/bcprov-jdk15on-1.54.jar"))) {
				JarEntry nextEntry = null;
				while ((nextEntry = is.getNextJarEntry()) != null) {
					final int est = (int) nextEntry.getSize();
					byte[] data = new byte[est > 0 ? est : 1024];
					int real = 0;
					for (int r = is.read(data); r > 0; r = is.read(data, real, data.length - real)) {
						if (data.length == (real += r)) {
							data = Arrays.copyOf(data, data.length * 2);
						}
					}
					if (real != data.length) {
						data = Arrays.copyOf(data, real);
					}
					map.put("/" + nextEntry.getName(), data);
				}
			}
			URL u = new URL("x-buffer", null, -1, "/", new URLStreamHandler() {
				@Override
				protected URLConnection openConnection(URL u) throws IOException {
					final byte[] data = map.get(u.getFile());
					if (data == null) {
						throw new FileNotFoundException(u.getFile());
					}
					return new URLConnection(u) {
						@Override
						public void connect() throws IOException {
						}

						@Override
						public InputStream getInputStream() throws IOException {
							return new ByteArrayInputStream(data);
						}
					};
				}
			});
			try (URLClassLoader cl = new URLClassLoader(new URL[] { u })) {
				final Class<?> bcp = Class.forName("org.bouncycastle.jce.provider.BouncyCastleProvider", true, cl);
				AccessController.doPrivileged(new PrivilegedAction<Void>() {
					@Override
					public Void run() {
						try {
							Security.addProvider((Provider) bcp.newInstance());
						} catch (InstantiationException | IllegalAccessException e) {
							e.printStackTrace();
						}
						return null;
					}
				});
				//bcp.newInstance();
				/*
				Class<?> c = Class.forName(CoreScreenShare.class.getName(), true, cl);
				@SuppressWarnings("unchecked")
				Constructor<CoreScreenShare> con = (Constructor<CoreScreenShare>)c.getConstructor(String[].class);
				con.newInstance(new Object[]{args});
				*/
			}
		} catch (Exception e) {
			e.printStackTrace();;
		}
	}
}