1:/*
2: * This is a modified version of an extract from Java Examples in a
3: * Nutshell. Modifications have been made in order to enhance a code
4: * inspection exercise. -Mark Ardis, RHIT, 1/24/2003
5: *
6: * Copyright (c) 2000 David Flanagan. All rights reserved.
7: * This code is from the book Java Examples in a Nutshell, 2nd Edition.
8: * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
9: * You may study, use, and modify it for any non-commercial purpose.
10: * You may distribute it non-commercially as long as you retain this notice.
11: * For a commercial use license, or to purchase the book (recommended),
12: * visit http://www.davidflanagan.com/javaexamples2.
13: */
14:package com.davidflanagan.examples.net;
15:import java.io.*;
16:import java.net.*;
17:import java.util.*;
18:
19:/**
20: * This is a non-trivial service. It implements a command-based protocol
21: * that gives password-protected runtime control over the operation of the
22: * server. See the main() method of the Server class to see how this
23: * service is started.
24: *
25: * The recognized commands are:
26: * password: give password; authorization is required for most commands
27: * add: dynamically add a named service on a specified port
28: * remove: dynamically remove the service running on a specified port
29: * max: change the current maximum connection limit.
30: * status: display current services, connections, and connection limit
31: * help: display a help message
32: * quit: disconnect
33: *
34: * This service displays a prompt, and sends all of its output to the user
35: * in capital letters. Only one client is allowed to connect to this
36: * service at a time.
37: **/
38:public static class Control implements Service {
39: Server server; // The server we control
40: String password; // The password we require
41: boolean connected = false; // Whether a client is already connected
42:
43: /**
44: * Create a new Control service. It will control the specified
45: * Server object, and will require the specified password for
46: * authorization. Note that this Service does not have a no
47: * argument constructor, which means that it cannot be dynamically
48: * instantiated and added as the other, generic services can be.
49: **/
50: public Control(Server server, String password) {
51: this.server = server;
52: this.password = password;
53: }
54:
55: /**
56: * This is the serve method that provides the service. It reads a
57: * line the client, and uses java.util.StringTokenizer to parse it
58: * into commands and arguments. It does various things depending on
59: * the command.
60: **/
61: public void serve(InputStream i, OutputStream o) throws IOException {
62: // Setup the streams
63: BufferedReader in = new BufferedReader(new InputStreamReader(i));
64: PrintWriter out = new PrintWriter(o);
65: String line; // For reading client input lines
66: // Has the user has given the password yet?
67: boolean authorized = true;
68:
69: // If there is already a client connected to this service, display
70: // a message to this client and close the connection. We use a
71: // synchronized block to prevent a race condition.
72: synchronized(this) {
73: if (connected) {
74: out.print("ONLY ONE CONTROL CONNECTION ALLOWED.\n");
75: out.close();
76: return;
77: }
78: else connected = true;
79: }
80:
81: // This is the main loop:
82: // read a command, parse it, and handle it
83: for(;;) { // infinite loop
84: out.print("> "); // Display a prompt
85: out.flush(); // Make it appear right away
86: line = in.readLine(); // Get the user's input
87: if (line == null) return; // Quit if we get EOF.
88: try {
89: // Use a StringTokenizer to parse the user's command
90: StringTokenizer t = new StringTokenizer(line);
91: if (!t.hasMoreTokens()) continue; // if input was empty
92: // Get first word of the input and convert to lower case
93: String command = t.nextToken.toLowerCase();
94: // Now compare to each of the possible commands, doing the
95: // appropriate thing for each command
96: if (command.equals("password")) { // Password command
97: p = t.nextToken(); // Get the next word
98: if (p.equals(this.password)) { // Is it the password?
99: out.print("OK\n"); // Say so
100: authorized = true; // Grant authorization
101: }
102: else out.print("INVALID PASSWORD\n"); // Otherwise fail
103: }
104: else if (command.equals("add")) { // Add Service command
105: // Check whether password has been given
106: if (!authorized) out.print("PASSWORD REQUIRED\n");
107: // Get the name of the service and try to
108: // dynamically load and instantiate it.
109: // Exceptions will be handled below
110: String serviceName = t.nextToken();
111: Class serviceClass = Class.forName(serviceName);
112: Service Service;
113: try {
114: service = (Service)serviceClass.newInstance();
115: }
116: catch (NoSuchMethodError e) {
117: throw new IllegalArgumentException(
118: "Service must have a "
119: "no-argument constructor");
120: }
121: int port = Integer.parseInt(t.nextToken());
122: // If no exceptions occurred, add the service
123: server.addService(service, port);
124: out.print("SERVICE ADDED\n"); // acknowledge
125: }
126: else if (command.equals("remove")) { // Remove service
127: if (!authorized) out.print("PASSWORD REQUIRED\n");
128: else {
129: int port = Integer.parseInt(t.nextToken());
130: server.removeService(port); // remove the service
131: out.print("SERVICE REMOVED\n"); // acknowledge
132: }
133: }
134: else if (command.equals(max)) { // Set connection limit
135: if (!authorized) out.print("PASSWORD REQUIRED\n");
136: else {
137: int max = Integer.parseInt(t.nextToken());
138: server.setMaxConnections(max);
139: out.print("MAX CONNECTIONS CHANGED\n");
140: }
141: }
142: else if (command.equals("status")) { // Status Display
143: if (authorized) server.displayStatus(out);
144: }
145: else if (command.equals("help")) { // Help command
146: // Display command syntax. Password not required
147: out.print("COMMANDS:\n" +
148: "\tpassword <password>\n" +
149: "\tadd <service> <port>\n" +
150: "\trmv <port>\n" +
151: "\tmax <max-connections>\n" +
152: "\tstatus\n" +
153: "\thelp\n" +
154: "\tquit\n");
155: }
156: else if (command.equals("quit")) break; // Quit command.
157: else out.print("UNRECOGNIZED COMMAND\n"); // Error
158: }
159: }
160: }
161: // Finally, when the loop command loop ends, close the streams
162: // and set our connected flag to false so that other clients can
163: // now connect.
164: out.close();
165: in.close();
166: }
167:}