Springsecurity之CasAuthenticationProvider

private List<AuthenticationProvider> providers

public Authentication authenticate(Authentication authentication)
		throws AuthenticationException {
	Class<? extends Authentication> toTest = authentication.getClass();
	AuthenticationException lastException = null;
	Authentication result = null;
	boolean debug = logger.isDebugEnabled();

	for (AuthenticationProvider provider : getProviders()) {
		if (!provider.supports(toTest)) {
			continue;
		}
		if (debug) {
			logger.debug("Authentication attempt using "
					+ provider.getClass().getName());
		}
		try {
			result = provider.authenticate(authentication);
			if (result != null) {
				copyDetails(authentication, result);
				break;
			}
		}
		catch (AccountStatusException e) {
			prepareException(e, authentication);
			// SEC-546: Avoid polling additional providers if auth failure is due to
			// invalid account status
			throw e;
		}
		catch (InternalAuthenticationServiceException e) {
			prepareException(e, authentication);
			throw e;
		}
		catch (AuthenticationException e) {
			lastException = e;
		}
	}