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package javax.security.auth.message.callback;

import java.math.BigInteger;
import java.security.Principal;
import javax.crypto.SecretKey;
import javax.security.auth.callback.Callback;

/**
 * Callback for acquiring a shared secret from a key repository.
 * This Callback may be used by client or server authentication modules 
 * to obtain shared secrets (for example, passwords) without relying on a 
 * user during the Callback processing. 
 * This Callback is typically empoyed by <code>ClientAuthModules</code>
 * invoked from intermediate components that need to acquire
 * a password to authenticate to their target service.
 *
 * @version %I%, %G%
 */
public class SecretKeyCallback implements Callback {

    private Request request;
    private SecretKey key;

    /**
     * Marker interface for secret key request types.
     */
    public static interface Request { };

    /**
     * Request type for secret keys that are identified using an alias.
     */
    public static class AliasRequest implements Request {
	private String alias;

	/**
	 * Construct an AliasRequest with an alias.
	 *
	 * <p> The alias is used to directly identify the secret key
	 * to be returned.
	 *
	 * <p> If the alias is null,
	 * the handler of the callback relies on its own default.
	 *
	 * @param alias Name identifier for the secret key, or null.
	 */
	public AliasRequest(String alias) {
	    this.alias = alias;
	}

	/**
	 * Get the alias.
	 *
	 * @return The alias, or null.
	 */
	public String getAlias() {
	    return alias;
	}
    }

    /**
     * Constructs this SecretKeyCallback with a secret key Request object.
     *
     * <p> The <i>request</i> object identifies the secret key
     * to be returned.
     *
     * If the alias is null, the handler of the callback
     * relies on its own default.
     *
     * @param request Request object identifying the secret key, or null.
     */
    public SecretKeyCallback(Request request) {
	this.request = request;
    }

    /**
     * Used by the CallbackHandler to get the Request object which identifies 
     * the secret key to be returned.
     *
     * @return The Request object which identifies the private key
     *		to be returned, or null.  If null, the handler of the callback
     *		relies on its own default.
     */
    public Request getRequest() {
	return request;
    }

    /**
     * Used by the CallbackHandler to set the requested secret key within
     * the Callback.
     *
     * @param key The secret key, or null if no key was found.
     */
    public void setKey(SecretKey key) {
	this.key = key;
    }

    /**
     * Used to obtain the secret key set within the Callback.
     *
     * @return The secret key, or null if no key was found.
     */
    public SecretKey getKey() {
	return key;
    }
}
