safeserver.java

java 的164个例子的源代码,包括了 很多方面,供包括了19个方面的 源代码

/*
 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit http://www.davidflanagan.com/javaexamples2.
 */
package com.davidflanagan.examples.security;
import com.davidflanagan.examples.net.Server;
import java.io.*;
import java.net.*;
import java.security.*;

/**
 * This class is a program that uses the Server class defined in Chapter 5.
 * Server would load arbitrary "Service" classes to provide services.
 * This class is an alternative program to start up a Server in a similar 
 * way.  The difference is that this one uses a SecurityManager and a 
 * ClassLoader to prevent the Service classes from doing anything damaging
 * or malicious on the local system.  This allows us to safely run Service 
 * classes that come from untrusted sources.
 **/
public class SafeServer {
    public static void main(String[] args) {
        try {
            // Install a Security manager, if the user didn't already install
	    // one with the -Djava.security.manager argument
	    if (System.getSecurityManager() == null) {
		System.out.println("Establishing a security manager");
		System.setSecurityManager(new SecurityManager());
	    }

            // Create a Server object
            Server server = new Server(null, 5);

            // Create the ClassLoader that we'll use to load Service classes.
            // The classes should be stored in the JAR file or the directory
            // specified as a URL by the first command-line argument
	    URL serviceURL = new URL(args[0]);
            ClassLoader loader =
		new java.net.URLClassLoader(new URL[] {serviceURL});

            // Parse the argument list, which should contain Service name/port
            // pairs.  For each pair, load the named Service using the class
            // loader, then instantiate it with newInstance(), then tell the
            // server to start running it.
            int i = 1;
            while(i < args.length) {
		// Dynamically load the Service class using the class loader
		Class serviceClass = loader.loadClass(args[i++]);      
		// Dynamically instantiate the class.  
                Server.Service service =
		    (Server.Service)serviceClass.newInstance();
                int port = Integer.parseInt(args[i++]);  // Parse the port #
                server.addService(service, port);        // Run service
            }
        }
        catch (Exception e) { // Display a message if anything goes wrong
            System.err.println(e);
            System.err.println("Usage: java " + SafeServer.class.getName() +
			       " <url> <servicename> <port>\n" +
			       "\t[<servicename> <port> ... ]");
            System.exit(1);
        }
    }
}