core/src/main/java/org/springframework/security/authentication/jaas/JaasPasswordCallbackHandler.java
public void handle(Callback callback, Authentication auth) throws IOException,
			UnsupportedCallbackException {
		if (callback instanceof PasswordCallback) {
			PasswordCallback pc = (PasswordCallback) callback;
			pc.setPassword(auth.getCredentials().toString().toCharArray());
		}
	}
public void handle(Callback callback, Authentication auth) throws IOException,
			UnsupportedCallbackException {
		if (callback instanceof PasswordCallback) {
			PasswordCallback pc = (PasswordCallback) callback;
			pc.setPassword(auth.getCredentials().toString().toCharArray());
		}
	}
If the callback passed to the 'handle' method is an instance of PasswordCallback,
the JaasPasswordCallbackHandler will call,
callback.setPassword(authentication.getCredentials().toString()).

@param callback
@param auth

@throws IOException
@throws UnsupportedCallbackException