UserNamePasswrodAuthenticationFilter验证过程

//ProviderManager.authenticate
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 (AuthenticationException e) {
                lastException = e;
            }
        }
        if (result == null && parent != null) {
            // Allow the parent to try.
            try {
                result = parent.authenticate(authentication);
            } catch (ProviderNotFoundException e) {
                // ignore as we will throw below if no other exception occurred prior to calling parent and the parent
                // may throw ProviderNotFound even though a provider in the child already handled the request
            } catch (AuthenticationException e) {
                lastException = e;
            }
        }
        if (result != null) {
            if (eraseCredentialsAfterAuthentication && (result instanceof CredentialsContainer)) {
                // Authentication is complete. Remove credentials and other secret data from authentication
                ((CredentialsContainer)result).eraseCredentials();
            }
            eventPublisher.publishAuthenticationSuccess(result);
            return result;
        }
        // Parent was null, or didn‘t authenticate (or throw an exception).
        if (lastException == null) {
            lastException = new ProviderNotFoundException(messages.getMessage("ProviderManager.providerNotFound",
                        new Object[] {toTest.getName()}, "No AuthenticationProvider found for {0}"));
        }
        prepareException(lastException, authentication);
        throw lastException;
    }