A Callback of this type represents a request to ask the user a yes/no or multiple-choice question. A CallbackHandler should first call getPrompt( ) to obtain the text of the question. It should also call getMessageType( ) to determine the message type (INFORMATION, WARNING, or ERROR) and present the question to the user in a suitable manner based on that type.

Next, the CallbackHandler must determine the appropriate set of responses to the question. It does this by calling getOptionType( ). The return values have the following meanings:

YES_NO_OPTION

The CallbackHandler should allow the user to respond to the question with a "yes" or a "no" (or their localized equivalents).

YES_NO_CANCEL_OPTION

The CallbackHandler should allow "yes", "no", and "cancel" (or their localized equivalents) responses.

OK_CANCEL_OPTION

The CallbackHandler should allow "ok" and "cancel" (or their localized equivalents) responses.

UNSPECIFIED_OPTION

The CallbackHandler should call getOptions( ) and use present all strings it returns as possible responses.

In each of these cases, the CallbackHandler should also call getdefaultOption( ) to determine which response should be presented as the default response. If getOptionType( ) returned UNSPECIFIED_TYPE, then getdefaultOption( ) returns an index into the array of options returned by getOptions( ). Otherwise getdefaultOption( ) returns one of the constants YES, NO, OK, or CANCEL.

When the user has selected a response to the callback, the CallbackHandler should pass that response to setSelectedIndex( ). The response value should be one of the constants YES, NO, OK, or CANCEL, or an index into the array of options returned by getOptions( ).

Figure 19-7. javax.security.auth.callback.ConfirmationCallback

public class ConfirmationCallback implements Callback, Serializable {
// Public Constructors
     public ConfirmationCallback(int messageType, String[ ] options, int defaultOption);  
     public ConfirmationCallback(int messageType, int optionType, int defaultOption);  
     public ConfirmationCallback(String prompt, int messageType, String[ ] options, 
        int defaultOption);  
     public ConfirmationCallback(String prompt, int messageType, int optionType,
        int defaultOption);  
// Public Constants
     public static final int CANCEL;                                     =2
     public static final int ERROR;                                      =2
     public static final int INFORMATION;                                =0
     public static final int NO;                                         =1
     public static final int OK;                                         =3
     public static final int OK_CANCEL_OPTION;                           =2
     public static final int UNSPECIFIED_OPTION;                         =-1
     public static final int WARNING;                                    =1
     public static final int YES;                                        =0
     public static final int YES_NO_CANCEL_OPTION;                       =1
     public static final int YES_NO_OPTION;                              =0
// Public Instance Methods
     public int getDefaultOption( );  
     public int getMessageType( );  
     public String[ ] getOptions( );  
     public int getOptionType( );  
     public String getPrompt( );  
     public int getSelectedIndex( );  
     public void setSelectedIndex(int selection);  
}