Java Reference
In-Depth Information
Example 5•9: Server.java (continued)
/**
* This is the serve method that provides the service. It reads a
* line the client, and uses java.util.StringTokenizer to parse it
* into commands and arguments. It does various things depending on
* the command.
**/
public void serve(InputStream i, OutputStream o) throws IOException {
// Setup the streams
BufferedReader in = new BufferedReader(new InputStreamReader(i));
PrintWriter out = new PrintWriter(o);
String line; // For reading client input lines
// Has the user has given the password yet?
boolean authorized = false;
// If there is already a client connected to this service, display
// a message to this client and close the connection. We use a
// synchronized block to prevent a race condition.
synchronized(this) {
if (connected) {
out.print("ONLY ONE CONTROL CONNECTION ALLOWED.\n");
out.close();
return;
}
else connected = true;
}
// This is the main loop: read a command, parse it, and handle it
for(;;) { // infinite loop
out.print("> ");
// Display a prompt
out.flush();
// Make it appear right away
line = in.readLine();
// Get the user's input
if (line == null) break;
// Quit if we get EOF.
try {
// Use a StringTokenizer to parse the user's command
StringTokenizer t = new StringTokenizer(line);
if (!t.hasMoreTokens()) continue; // if input was empty
// Get first word of the input and convert to lower case
String command = t.nextToken().toLowerCase();
// Now compare to each of the possible commands, doing the
// appropriate thing for each command
if (command.equals("password")) { // Password command
String p = t.nextToken(); // Get the next word
if (p.equals(this.password)) { // Is it the password?
out.print("OK\n");
// Say so
authorized = true;
// Grant authorization
}
else out.print("INVALID PASSWORD\n"); // Otherwise fail
}
else if (command.equals("add")) { // Add Service command
// Check whether password has been given
if (!authorized) out.print("PASSWORD REQUIRED\n");
else {
// Get the name of the service and try to
// dynamically load and instantiate it.
// Exceptions will be handled below
String serviceName = t.nextToken();
Class serviceClass = Class.forName(serviceName);
Service service;
