handlecb.html

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<TITLE>Handling the Callbacks from a Login Module
(Java Developers Almanac Example)
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    <B><A HREF="../javax.security.auth.login/pkg.html">javax.security.auth.login</A></B><font color="#666666" SIZE="-2">
        &nbsp;[3 examples]
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  <h3>
    e509.  
    Handling the Callbacks from a Login Module</h3>

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


<pre>
    // 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&lt;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(<font color="#0066ff"><i>"username"</i></font>);
                } 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(<font color="#0066ff"><i>"password"</i></font>.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(<font color="#0066ff"><i>Locale.CHINESE</i></font>);
                } else {
                    throw new UnsupportedCallbackException(callbacks[i], "Unrecognized Callback");
                }
            }
        }
    }
</pre>
Here's an example that uses the callback handler:

<pre>
    try {
        // Create login context
        LoginContext lc = new LoginContext(<font color="#0066ff"><i>"LoginAppName"</i></font>,
            new MyCallbackHandler());
    } catch (LoginException e) {
        // Login failed
    }
</pre>
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            &nbsp;Related Examples
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e507. <a class="eglink" href="ListAppNames.html?l=rel">
    Listing the Login Modules of an Entry in the Current Login Configuration
</a>
<br>

e508. <a class="eglink" href="GetLogin.html?l=rel">
    Getting the Login Name of the Currently Logged-In User
</a>
<br>


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