Spring Security原理与应用

public interface AuthenticationManager {
	Authentication authenticate(Authentication authentication)
			throws AuthenticationException;
}

验证逻辑

AuthenticationManager 接收 Authentication 对象作为参数，并通过 authenticate(Authentication) 方法对其进行验证；AuthenticationProvider实现类用来支撑对 Authentication 对象的验证动作；UsernamePasswordAuthenticationToken实现了 Authentication主要是将用户输入的用户名和密码进行封装，并供给 AuthenticationManager 进行验证；验证完成以后将返回一个认证成功的 Authentication 对象；

ProviderManager

它是 AuthenticationManager 的一个实现类，提供了基本的认证逻辑和方法；它包含了一个 List<AuthenticationProvider> 对象，通过 AuthenticationProvider 接口来扩展出不同的认证提供者(当Spring Security默认提供的实现类不能满足需求的时候可以扩展AuthenticationProvider 覆盖supports(Class<?> authentication) 方法)；

实现逻辑

public Authentication authenticate(Authentication authentication)
			throws AuthenticationException {
		//#1.获取当前的Authentication的认证类型
		Class<? extends Authentication> toTest = authentication.getClass();
		AuthenticationException lastException = null;
		Authentication result = null;
		boolean debug = logger.isDebugEnabled();
		//#2.遍历所有的providers使用supports方法判断该provider是否支持当前的认证类型，不支持的话继续遍历
		for (AuthenticationProvider provider : getProviders()) {
			if (!provider.supports(toTest)) {
				continue;
			}

			if (debug) {
				logger.debug("Authentication attempt using "
						+ provider.getClass().getName());
			}

			try {
				#3.支持的话调用provider的authenticat方法认证
				result = provider.authenticate(authentication);

				if (result != null) {
					#4.认证通过的话重新生成Authentication对应的Token
					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;
			}
		}

		if (result == null && parent != null) {
			// Allow the parent to try.
			try {
				#5.如果#1 没有验证通过，则使用父类型AuthenticationManager进行验证
				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;
			}
		}
		#6. 是否擦出敏感信息
		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;
	}
说明：

1. 遍历所有的 Providers，然后依次执行该 Provider 的验证方法
   • 如果某一个 Provider 验证成功，则跳出循环不再执行后续的验证；
   • 如果验证成功，会将返回的 result 既 Authentication 对象进一步封装为 Authentication Token； 比如 UsernamePasswordAuthenticationToken、RememberMeAuthenticationToken 等；这些 Authentication Token 也都继承自 Authentication 对象；
2. 如果 #1 没有任何一个 Provider 验证成功，则试图使用其 parent Authentication Manager 进行验证；
3. 是否需要擦除密码等敏感信息；