Spring Security基于数据库验证流程详解

Spring Security 校验流程图

相关解释说明（认真看哦）

AbstractAuthenticationProcessingFilter 抽象类

/*** 调用 #requiresAuthentication(HttpServletRequest, HttpServletResponse) 决定是否需要进行验证操作。* 如果需要验证，则会调用 #attemptAuthentication(HttpServletRequest, HttpServletResponse) 方法。* 有三种结果：* 1、返回一个 Authentication 对象。* 配置的 SessionAuthenticationStrategy` 将被调用，* 然后 然后调用 #successfulAuthentication(HttpServletRequest，HttpServletResponse，FilterChain，Authentication) 方法。* 2、验证时发生 AuthenticationException。* #unsuccessfulAuthentication(HttpServletRequest, HttpServletResponse, AuthenticationException) 方法将被调用。* 3、返回Null，表示身份验证不完整。假设子类做了一些必要的工作（如重定向）来继续处理验证，方法将立即返回。* 假设后一个请求将被这种方法接收，其中返回的Authentication对象不为空。*/public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)throws IOException, ServletException {HttpServletRequest request = (HttpServletRequest) req;HttpServletResponse response = (HttpServletResponse) res;if (!requiresAuthentication(request, response)) {chain.doFilter(request, response);return;}if (logger.isDebugEnabled()) {logger.debug("Request is to process authentication");}Authentication authResult;try {authResult = attemptAuthentication(request, response);if (authResult == null) {// return immediately as subclass has indicated that it hasn't completed// authenticationreturn;}sessionStrategy.onAuthentication(authResult, request, response);}catch (InternalAuthenticationServiceException failed) {logger.error("An internal error occurred while trying to authenticate the user.",failed);unsuccessfulAuthentication(request, response, failed);return;}catch (AuthenticationException failed) {// Authentication failedunsuccessfulAuthentication(request, response, failed);return;}// Authentication successif (continueChainBeforeSuccessfulAuthentication) {chain.doFilter(request, response);}successfulAuthentication(request, response, chain, authResult);}

UsernamePasswordAuthenticationFilter（AbstractAuthenticationProcessingFilter的子类）

public Authentication attemptAuthentication(HttpServletRequest request,HttpServletResponse response) throws AuthenticationException {if (postOnly && !request.getMethod().equals("POST")) {throw new AuthenticationServiceException("Authentication method not supported: " + request.getMethod());}String username = obtainUsername(request);String password = obtainPassword(request);if (username == null) {username = "";}if (password == null) {password = "";}username = username.trim();UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(username, password);// Allow subclasses to set the "details" propertysetDetails(request, authRequest);return this.getAuthenticationManager().authenticate(authRequest);}

#attemptAuthentication () 方法将 request 中的 username 和 password 生成 UsernamePasswordAuthenticationToken 对象，用于 AuthenticationManager 的验证（即 this.getAuthenticationManager().authenticate(authRequest) ）。

默认情况下注入 Spring 容器的 AuthenticationManager 是 ProviderManager。

ProviderManager（AuthenticationManager的实现类）

/*** 尝试验证 Authentication 对象* AuthenticationProvider 列表将被连续尝试，直到 AuthenticationProvider 表示它能够认证传递的过来的Authentication 对象。然后将使用该 AuthenticationProvider 尝试身份验证。* 如果有多个 AuthenticationProvider 支持验证传递过来的Authentication 对象，那么由第一个来确定结果，覆盖早期支持AuthenticationProviders 所引发的任何可能的AuthenticationException。 成功验证后，将不会尝试后续的AuthenticationProvider。* 如果最后所有的 AuthenticationProviders 都没有成功验证 Authentication 对象，将抛出 AuthenticationException。*/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 statusthrow 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 {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;}

从代码中不难看出，由 provider 来验证 authentication， 核心点方法是：

Authentication result = provider.authenticate(authentication);

此处的 provider 是 AbstractUserDetailsAuthenticationProvider，
AbstractUserDetailsAuthenticationProvider 是AuthenticationProvider的实现，看看它的 #authenticate(authentication) 方法：

// 验证 authentication
public Authentication authenticate(Authentication authentication)throws AuthenticationException {Assert.isInstanceOf(UsernamePasswordAuthenticationToken.class, authentication,messages.getMessage("AbstractUserDetailsAuthenticationProvider.onlySupports","Only UsernamePasswordAuthenticationToken is supported"));// Determine usernameString username = (authentication.getPrincipal() == null) ? "NONE_PROVIDED": authentication.getName();boolean cacheWasUsed = true;UserDetails user = this.userCache.getUserFromCache(username);if (user == null) {cacheWasUsed = false;try {user = retrieveUser(username,(UsernamePasswordAuthenticationToken) authentication);}catch (UsernameNotFoundException notFound) {logger.debug("User '" + username + "' not found");if (hideUserNotFoundExceptions) {throw new BadCredentialsException(messages.getMessage("AbstractUserDetailsAuthenticationProvider.badCredentials","Bad credentials"));}else {throw notFound;}}Assert.notNull(user,"retrieveUser returned null - a violation of the interface contract");}try {preAuthenticationChecks.check(user);additionalAuthenticationChecks(user,(UsernamePasswordAuthenticationToken) authentication);}catch (AuthenticationException exception) {if (cacheWasUsed) {// There was a problem, so try again after checking// we're using latest data (i.e. not from the cache)cacheWasUsed = false;user = retrieveUser(username,(UsernamePasswordAuthenticationToken) authentication);preAuthenticationChecks.check(user);additionalAuthenticationChecks(user,(UsernamePasswordAuthenticationToken) authentication);}else {throw exception;}}postAuthenticationChecks.check(user);if (!cacheWasUsed) {this.userCache.putUserInCache(user);}Object principalToReturn = user;if (forcePrincipalAsString) {principalToReturn = user.getUsername();}return createSuccessAuthentication(principalToReturn, authentication, user);}

AbstractUserDetailsAuthenticationProvider 内置了缓存机制，从缓存中获取不到的 UserDetails 信息的话，就调用如下方法获取用户信息，然后和 用户传来的信息进行对比来判断是否验证成功。

// 获取用户信息
UserDetails user = retrieveUser(username,(UsernamePasswordAuthenticationToken) authentication);

#retrieveUser() 方法在 DaoAuthenticationProvider 中实现，DaoAuthenticationProvider 是 AbstractUserDetailsAuthenticationProvider的子类。具体实现如下：

protected final UserDetails retrieveUser(String username,UsernamePasswordAuthenticationToken authentication)throws AuthenticationException {UserDetails loadedUser;try {loadedUser = this.getUserDetailsService().loadUserByUsername(username);}catch (UsernameNotFoundException notFound) {if (authentication.getCredentials() != null) {String presentedPassword = authentication.getCredentials().toString();passwordEncoder.isPasswordValid(userNotFoundEncodedPassword,presentedPassword, null);}throw notFound;}catch (Exception repositoryProblem) {throw new InternalAuthenticationServiceException(repositoryProblem.getMessage(), repositoryProblem);}if (loadedUser == null) {throw new InternalAuthenticationServiceException("UserDetailsService returned null, which is an interface contract violation");}return loadedUser;}

可以看到此处的返回对象 userDetails 是由 UserDetailsService 的 #loadUserByUsername(username) 来获取的。