在Spring Security中，认证授权都是通过过滤器来实现的。
当开始登陆的时候，有一个关键的过滤器UsernamePasswordAuthenticationFilter，该类继承抽象类AbstractAuthenticationProcessingFilter，在AbstractAuthenticationProcessingFilter里有一个doFilter方法，一切先从这里说起。
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private void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException { if (!requiresAuthentication(request, response)) { chain.doFilter(request, response); return; } try { Authentication authenticationResult = attemptAuthentication(request, response); if (authenticationResult == null) { // return immediately as subclass has indicated that it hasn't completed return; } this.sessionStrategy.onAuthentication(authenticationResult, request, response); // Authentication success if (this.continueChainBeforeSuccessfulAuthentication) { chain.doFilter(request, response); } successfulAuthentication(request, response, chain, authenticationResult); } catch (InternalAuthenticationServiceException failed) { this.logger.error("An internal error occurred while trying to authenticate the user.", failed); unsuccessfulAuthentication(request, response, failed); } catch (AuthenticationException ex) { // Authentication failed unsuccessfulAuthentication(request, response, ex); }} |
首先requiresAuthentication先判断是否尝试校验，通过后调用attemptAuthentication方法，这个方法也就是UsernamePasswordAuthenticationFilter 中的attemptAuthentication方法。
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public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException { if (this.postOnly && !request.getMethod().equals("POST")) { throw new AuthenticationServiceException("Authentication method not supported: " + request.getMethod()); } String username = obtainUsername(request); username = (username != null) ? username : ""; username = username.trim(); String password = obtainPassword(request); password = (password != null) ? password : ""; UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(username, password); // Allow subclasses to set the "details" property setDetails(request, authRequest); return this.getAuthenticationManager().authenticate(authRequest);} |
1.在UsernamePasswordAuthenticationFilter 的attemptAuthentication方法中，先是验证请求的类型，是否是POST请求，如果不是的话，抛出异常。(PS：登陆肯定要用POST方法了)
2.然后拿到username和password。这里使用的是obtainUsername方法，也就是get方法。
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@Nullableprotected String obtainPassword(HttpServletRequest request) { return request.getParameter(this.passwordParameter);}@Nullableprotected String obtainUsername(HttpServletRequest request) { return request.getParameter(this.usernameParameter);} |
由此我们知道了Spring Security中是通过get方法来拿到参数，所以在进行前后端分离的时候是无法接受JSON数据，处理方法就是自定义一个Filter来继承UsernamePasswordAuthenticationFilter，重写attemptAuthentication方法，然后创建一个Filter实例写好登陆成功和失败的逻辑处理，在HttpSecurity参数的configure中通过addFilterAt来替换Spring Security官方提供的过滤器。
3.创建一个UsernamePasswordAuthenticationToken 实例。
4.设置Details，在这里关键的是在WebAuthenticationDetails类中记录了用户的remoteAddress和sessionId。
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public WebAuthenticationDetails(HttpServletRequest request) { this.remoteAddress = request.getRemoteAddr(); HttpSession session = request.getSession(false); this.sessionId = (session != null) ? session.getId() : null;} |
5.拿到一个AuthenticationManager通过authenticate方法进行校验，这里以实现类ProviderManager为例。
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@Overridepublic Authentication authenticate(Authentication authentication) throws AuthenticationException { //获取Authentication的运行时类 Class<? extends Authentication> toTest = authentication.getClass(); AuthenticationException lastException = null; AuthenticationException parentException = null; Authentication result = null; Authentication parentResult = null; int currentPosition = 0; int size = this.providers.size(); for (AuthenticationProvider provider : getProviders()) { //判断是否支持处理该类别的provider if (!provider.supports(toTest)) { continue; } if (logger.isTraceEnabled()) { logger.trace(LogMessage.format("Authenticating request with %s (%d/%d)", provider.getClass().getSimpleName(), ++currentPosition, size)); } try { //获取用户的信息 result = provider.authenticate(authentication); if (result != null) { copyDetails(authentication, result); break; } } catch (AccountStatusException | InternalAuthenticationServiceException ex) { prepareException(ex, authentication); // SEC-546: Avoid polling additional providers if auth failure is due to // invalid account status throw ex; } catch (AuthenticationException ex) { lastException = ex; } } //不支持的话跳出循环再次执行 if (result == null && this.parent != null) { // Allow the parent to try. try { parentResult = this.parent.authenticate(authentication); result = parentResult; } catch (ProviderNotFoundException ex) { // 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 ex) { parentException = ex; lastException = ex; } } if (result != null) { //擦除用户的凭证 也就是密码 if (this.eraseCredentialsAfterAuthentication && (result instanceof CredentialsContainer)) { // Authentication is complete. Remove credentials and other secret data // from authentication ((CredentialsContainer) result).eraseCredentials(); } // If the parent AuthenticationManager was attempted and successful then it // will publish an AuthenticationSuccessEvent // This check prevents a duplicate AuthenticationSuccessEvent if the parent // AuthenticationManager already published it if (parentResult == null) { //公示登陆成功 this.eventPublisher.publishAuthenticationSuccess(result); } return result; } // Parent was null, or didn't authenticate (or throw an exception). if (lastException == null) { lastException = new ProviderNotFoundException(this.messages.getMessage("ProviderManager.providerNotFound", new Object[] { toTest.getName() }, "No AuthenticationProvider found for {0}")); } // If the parent AuthenticationManager was attempted and failed then it will // publish an AbstractAuthenticationFailureEvent // This check prevents a duplicate AbstractAuthenticationFailureEvent if the // parent AuthenticationManager already published it if (parentException == null) { prepareException(lastException, authentication); } throw lastException;} |
6.经过一系列校验，此时登陆校验基本完成，当验证通过后会执行doFilter中的successfulAuthentication方法，跳转到我们设置的登陆成功界面，验证失败会执行unsuccessfulAuthentication方法，跳转到我们设置的登陆失败界面。
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原文链接：https://blog.csdn.net/MAKEJAVAMAN/article/details/121021287
