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e509. Handling the Callbacks from a Login Module

This example implements a class that handles a few types of callbacks from a login module.

    // This login-module callback handler handles a few types of callbacks
    public class MyCallbackHandler implements CallbackHandler {
        public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {
            for (int i=0; i<callbacks.length; i++) {
                if (callbacks[i] instanceof TextOutputCallback) {
                    // This callback delivers messages from a login module
                    TextOutputCallback toCb = (TextOutputCallback)callbacks[i];
    
                    // Get message
                    String msg = toCb.getMessage();
    
                    // Get message type
                    switch (toCb.getMessageType()) {
                      case TextOutputCallback.INFORMATION:
                        break;
                      case TextOutputCallback.ERROR:
                        break;
                      case TextOutputCallback.WARNING:
                        break;
                    }
    
                    // Display message to the user ...
                } else if (callbacks[i] instanceof NameCallback) {
                    // A login module is requesting the name of the user
                    NameCallback nCb = (NameCallback)callbacks[i];
    
                    // Get the prompt to display to the user
                    String prompt = nCb.getPrompt();
    
                    // Get the name ...
    
                    // Set the name
                    nCb.setName("username");
                } else if (callbacks[i] instanceof PasswordCallback) {
                    // A login module is requesting the user's password
                    PasswordCallback pCb = (PasswordCallback)callbacks[i];
    
                    // Get the prompt to display to the user
                    String prompt = pCb.getPrompt();
    
                    // Get the password ...
    
                    // Set the password
                    pCb.setPassword("password".toCharArray());
                } else if (callbacks[i] instanceof LanguageCallback) {
                    // A login module is requesting the user's locale
                    LanguageCallback lCb = (LanguageCallback)callbacks[i];
    
                    // Get the locale ...
    
                    // Set the locale
                    lCb.setLocale(Locale.CHINESE);
                } else {
                    throw new UnsupportedCallbackException(callbacks[i], "Unrecognized Callback");
                }
            }
        }
    }

Here's an example that uses the callback handler:

    try {
        // Create login context
        LoginContext lc = new LoginContext("LoginAppName",
            new MyCallbackHandler());
    } catch (LoginException e) {
        // Login failed
    }

Related Examples

e507. Listing the Login Modules of an Entry in the Current Login Configuration
e508. Getting the Login Name of the Currently Logged-In User

© 2002 Addison-Wesley.