SpringSecurity 默认表单登录页展示流程源码

SpringSecurity 默认表单登录页展示流程源码

本篇主要讲解 SpringSecurity提供的默认表单登录页 它是如何展示的的流程，
涉及

1.FilterSecurityInterceptor，
2.ExceptionTranslationFilc,xmccmc,ter ，
3.DefaultLoginPageGeneratingFilter 过滤器，
并且简单介绍了 AccessDecisionManager 投票机制

 1.准备工作（体验SpringSecurity默认表单认证）

  1.1 创建SpringSecurity项目

  先通过IDEA 创建一个SpringBoot项目 并且依赖SpringSecurity，Web依赖

  此时pom.xml会自动添加

<dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-security</artifactId>
</dependency>

  1.2 提供一个接口

@RestController
public class HelloController {

@RequestMapping("/hello")
public String hello() {
 return "Hello SpringSecurity";
 }
}

，

  1.3 启动项目

  直接访问 提供的接口

http://localhost:8080/hello

  会发现浏览器被直接重定向到了 /login 并且显示如下默认的表单登录页

http://localhost:8080/login

  1.4 登录

  在启动项目的时候 控制台会打印一个 seuciryt password ： xxx

Using generated security password: f520875f-ea2b-4b5d-9b0c-f30c0c17b90b

  直接登录

用户名：user 密码 ：f520875f-ea2b-4b5d-9b0c-f30c0c17b90b

  登录成功并且 浏览器又会重定向到 刚刚访问的接口

 2.springSecurityFilterchain 过滤器链

 如果你看过我另一篇关于SpringSecurity初始化源码的博客，那么你一定知道当SpringSecurity项目启动完成后会初始化一个 springSecurityFilterchain 它内部 additionalFilters属性初始化了很多Filter 如下
所有的请求都会经过这一系列的过滤器 Spring Security就是通过这些过滤器 来进行认证授权等

 3.FilterSecurityInterceptor （它会判断这次请求能否通过）

 FilterSecurityInterceptor是过滤器链中最后一个过滤器，主要用于判断请求能否通过，内部通过AccessDecisionManager 进行投票判断

 当我们未登录访问

http://localhost:8080/hello

 请求会被 FilterSecurityInterceptor 拦截

public void doFilter(ServletRequest request, ServletResponse response,
 FilterChain chain) throws IOException, ServletException {
 FilterInvocation fi = new FilterInvocation(request, response, chain);
 invoke(fi);
}

 重点看invoke方法

public void invoke(FilterInvocation fi) throws IOException, ServletException {
 if ((fi.getRequest() != null)
  && (fi.getRequest().getAttribute(FILTER_APPLIED) != null)
  && observeOncePerRequest) {
 // filter already applied to this request and user wants us to observe
 // once-per-request handling, so don't re-do security checking
 fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
 }
 else {
 // first time this request being called, so perform security checking
 if (fi.getRequest() != null && observeOncePerRequest) {
  fi.getRequest().setAttribute(FILTER_APPLIED, Boolean.TRUE);
 }

 InterceptorStatusToken token = super.beforeInvocation(fi);

 try {
  fi.getChain().doFilter(fi.getRequest(), fi.getResponse());
 }
 finally {
  super.finallyInvocation(token);
 }

 super.afterInvocation(token, null);
 }
}

 源码中有这样一句，其实就是判断当前用户是否能够访问指定的接口，可以则执行 fi.getChain().doFilter 调用访问的接口
否则 内部会抛出异常

InterceptorStatusToken token = super.beforeInvocation(fi);

 beforeInvocation 方法内部是通过 accessDecisionManager 去做决定的
 Spring Security已经内置了几个基于投票的AccessDecisionManager包括（AffirmativeBased ，ConsensusBased ，UnanimousBased）当然如果需要你也可以实现自己的AccessDecisionManager

 使用这种方式，一系列的AccessDecisionVoter将会被AccessDecisionManager用来对Authentication是否有权访问受保护对象进行投票，然后再根据投票结果来决定是否要抛出AccessDeniedException

this.accessDecisionManager.decide(authenticated, object, attributes);

 AffirmativeBased的 decide的实现如下

public void decide(Authentication authentication, Object object, Collection<ConfigAttribute> configAttributes) throws AccessDeniedException {
 int deny = 0;
 Iterator var5 = this.getDecisionVoters().iterator();

 while(var5.hasNext()) {
 AccessDecisionVoter voter = (AccessDecisionVoter)var5.next();
 int result = voter.vote(authentication, object, configAttributes);
 if (this.logger.isDebugEnabled()) {
  this.logger.debug("Voter: " + voter + ", returned: " + result);
 }

 switch(result) {
 case -1:
  ++deny;
  break;
 case 1:
  return;
 }
 }

 if (deny > 0) {
 throw new AccessDeniedException(this.messages.getMessage("AbstractAccessDecisionManager.accessDenied", "Access is denied"));
 } else {
 this.checkAllowIfAllAbstainDecisions();
 }
}

 AffirmativeBased的逻辑是这样的：

（1）只要有AccessDecisionVoter的投票为ACCESS_GRANTED则同意用户进行访问；
（2）如果全部弃权也表示通过；
（3）如果没有一个人投赞成票，但是有人投反对票，则将抛出AccessDeniedException。

 当我们第一次访问的时候

http://localhost:8080/hello的时候

 返回 result = -1 会抛出 AccessDeniedException 拒绝访问异常

 4.ExceptionTranslationFilter （捕获AccessDeniedException异常）

 该过滤器它会接收到FilterSecurityInterceptor抛出的 AccessDeniedException异常）并且进行捕获，然后发送重定向到/login请求

 源码如下：

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
 throws IOException, ServletException {
 HttpServletRequest request = (HttpServletRequest) req;
 HttpServletResponse response = (HttpServletResponse) res;

 try {
 chain.doFilter(request, response);

 logger.debug("Chain processed normally");
 }
 catch (IOException ex) {
 throw ex;
 }
 catch (Exception ex) {
 // Try to extract a SpringSecurityException from the stacktrace
 Throwable[] causeChain = throwableAnalyzer.determineCauseChain(ex);
 RuntimeException ase = (AuthenticationException) throwableAnalyzer
  .getFirstThrowableOfType(AuthenticationException.class, causeChain);

 if (ase == null) {
  ase = (AccessDeniedException) throwableAnalyzer.getFirstThrowableOfType(
   AccessDeniedException.class, causeChain);
 }

 if (ase != null) {
  if (response.isCommitted()) {
  throw new ServletException("Unable to handle the Spring Security Exception because the response is already committed.", ex);
  }
  handleSpringSecurityException(request, response, chain, ase);
 }
 else {
  // Rethrow ServletExceptions and RuntimeExceptions as-is
  if (ex instanceof ServletException) {
  throw (ServletException) ex;
  }
  else if (ex instanceof RuntimeException) {
  throw (RuntimeException) ex;
  }

  // Wrap other Exceptions. This shouldn't actually happen
  // as we've already covered all the possibilities for doFilter
  throw new RuntimeException(ex);
 }
 }
}

 当获取异常后 调用

handleSpringSecurityException(request, response, chain, ase);

 handleSpringSecurityException 源码如下：

private void handleSpringSecurityException(HttpServletRequest request,
 HttpServletResponse response, FilterChain chain, RuntimeException exception)
 throws IOException, ServletException {
 if (exception instanceof AuthenticationException) {
 logger.debug(
  "Authentication exception occurred; redirecting to authentication entry point",
  exception);

 sendStartAuthentication(request, response, chain,
  (AuthenticationException) exception);
 }
 else if (exception instanceof AccessDeniedException) {
 Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
 if (authenticationTrustResolver.isAnonymous(authentication) || authenticationTrustResolver.isRememberMe(authentication)) {
  logger.debug(
   "Access is denied (user is " + (authenticationTrustResolver.isAnonymous(authentication) ? "anonymous" : "not fully authenticated") + "); redirecting to authentication entry point",
   exception);

  sendStartAuthentication(
   request,
   response,
   chain,
   new InsufficientAuthenticationException(
   messages.getMessage(
    "ExceptionTranslationFilter.insufficientAuthentication",
    "Full authentication is required to access this resource")));
 }
 else {
  logger.debug(
   "Access is denied (user is not anonymous); delegating to AccessDeniedHandler",
   exception);

  accessDeniedHandler.handle(request, response,
   (AccessDeniedException) exception);
 }
 }
}

 先判断获取的异常是否是AccessDeniedException 再判断是否是匿名用户，如果是则调用 sendStartAuthentication 重定向到登录页面

 重定向登录页面之前会保存当前访问的路径，这就是为什么我们访问 /hello接口后 再登录成功后又会跳转到 /hello接口，因为在重定向到/login接口前 这里进行了保存 requestCache.saveRequest(request, response);

protected void sendStartAuthentication(HttpServletRequest request,
 HttpServletResponse response, FilterChain chain,
 AuthenticationException reason) throws ServletException, IOException {
 // SEC-112: Clear the SecurityContextHolder's Authentication, as the
 // existing Authentication is no longer considered valid
 SecurityContextHolder.getContext().setAuthentication(null);
 requestCache.saveRequest(request, response);
 logger.debug("Calling Authentication entry point.");
 authenticationEntryPoint.commence(request, response, reason);
}

 authenticationEntryPoint.commence(request, response, reason);方法内部

 调用LoginUrlAuthenticationEntryPoint 的 commence方法

 LoginUrlAuthenticationEntryPoint 的commence方法内部有 构造重定向URL的方法

redirectUrl = buildRedirectUrlToLoginPage(request, response, authException);

protected String buildRedirectUrlToLoginPage(HttpServletRequest request,
 HttpServletResponse response, AuthenticationException authException) {

 String loginForm = determineUrlToUseForThisRequest(request, response,
  authException);

protected String determineUrlToUseForThisRequest(HttpServletRequest request,
 HttpServletResponse response, AuthenticationException exception) {

 return getLoginFormUrl();
}

 最终会获取到需要重定向的URL /login

 然后sendRedirect 既会重定向到 /login 请求

 5.DefaultLoginPageGeneratingFilter （会捕获重定向的/login 请求）

 DefaultLoginPageGeneratingFilter是过滤器链中的一个用于捕获/login请求,并且渲染出一个默认表单页面

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
 throws IOException, ServletException {
 HttpServletRequest request = (HttpServletRequest) req;
 HttpServletResponse response = (HttpServletResponse) res;

 boolean loginError = isErrorPage(request);
 boolean logoutSuccess = isLogoutSuccess(request);
 if (isLoginUrlRequest(request) || loginError || logoutSuccess) {
 String loginPageHtml = generateLoginPageHtml(request, loginError,
  logoutSuccess);
 response.setContentType("text/html;charset=UTF-8");
 response.setContentLength(loginPageHtml.getBytes(StandardCharsets.UTF_8).length);
 response.getWriter().write(loginPageHtml);

 return;
 }

 chain.doFilter(request, response);
}

 isLoginUrlRequest 判断请求是否是 loginPageUrl

private boolean isLoginUrlRequest(HttpServletRequest request) {
 return matches(request, loginPageUrl);
}

 因为我们没有配置所以 默认的 loginPageUrl = /login

 验证通过请求路径 能匹配 loginPageUrl

String loginPageHtml = generateLoginPageHtml(request, loginError,
  logoutSuccess);

 generateLoginPageHtml 绘制默认的HTML 页面，到此我们默认的登录页面怎么来的就解释清楚了

private String generateLoginPageHtml(HttpServletRequest request, boolean loginError,
  boolean logoutSuccess) {
 String errorMsg = "Invalid credentials";

 if (loginError) {
  HttpSession session = request.getSession(false);

  if (session != null) {
   AuthenticationException ex = (AuthenticationException) session
     .getAttribute(WebAttributes.AUTHENTICATION_EXCEPTION);
   errorMsg = ex != null ? ex.getMessage() : "Invalid credentials";
  }
 }

 StringBuilder sb = new StringBuilder();

 sb.append("<!DOCTYPE html>\n"
   + "<html lang=\"en\">\n"
   + " <head>\n"
   + " <meta charset=\"utf-8\">\n"
   + " <meta name=\"viewport\" content=\"width=device-width, initial-scale=1, shrink-to-fit=no\">\n"
   + " <meta name=\"description\" content=\"\">\n"
   + " <meta name=\"author\" content=\"\">\n"
   + " <title>Please sign in</title>\n"
   + " <link href=\"https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css\" rel=\"stylesheet\" integrity=\"sha384-/Y6pD6FV/Vv2HJnA6t+vslU6fwYXjCFtcEpHbNJ0lyAFsXTsjBbfaDjzALeQsN6M\" crossorigin=\"anonymous\">\n"
   + " <link href=\"https://getbootstrap.com/docs/4.0/examples/signin/signin.css\" rel=\"stylesheet\" crossorigin=\"anonymous\"/>\n"
   + " </head>\n"
   + " <body>\n"
   + "  <div class=\"container\">\n");

 String contextPath = request.getContextPath();
 if (this.formLoginEnabled) {
  sb.append("  <form class=\"form-signin\" method=\"post\" action=\"" + contextPath + this.authenticationUrl + "\">\n"
    + "  <h2 class=\"form-signin-heading\">Please sign in</h2>\n"
    + createError(loginError, errorMsg)
    + createLogoutSuccess(logoutSuccess)
    + "  <p>\n"
    + "   <label for=\"username\" class=\"sr-only\">Username</label>\n"
    + "   <input type=\"text\" id=\"username\" name=\"" + this.usernameParameter + "\" class=\"form-control\" placeholder=\"Username\" required autofocus>\n"
    + "  </p>\n"
    + "  <p>\n"
    + "   <label for=\"password\" class=\"sr-only\">Password</label>\n"
    + "   <input type=\"password\" id=\"password\" name=\"" + this.passwordParameter + "\" class=\"form-control\" placeholder=\"Password\" required>\n"
    + "  </p>\n"
    + createRememberMe(this.rememberMeParameter)
    + renderHiddenInputs(request)
    + "  <button class=\"btn btn-lg btn-primary btn-block\" type=\"submit\">Sign in</button>\n"
    + "  </form>\n");
 }

 if (openIdEnabled) {
  sb.append("  <form name=\"oidf\" class=\"form-signin\" method=\"post\" action=\"" + contextPath + this.openIDauthenticationUrl + "\">\n"
    + "  <h2 class=\"form-signin-heading\">Login with OpenID Identity</h2>\n"
    + createError(loginError, errorMsg)
    + createLogoutSuccess(logoutSuccess)
    + "  <p>\n"
    + "   <label for=\"username\" class=\"sr-only\">Identity</label>\n"
    + "   <input type=\"text\" id=\"username\" name=\"" + this.openIDusernameParameter + "\" class=\"form-control\" placeholder=\"Username\" required autofocus>\n"
    + "  </p>\n"
    + createRememberMe(this.openIDrememberMeParameter)
    + renderHiddenInputs(request)
    + "  <button class=\"btn btn-lg btn-primary btn-block\" type=\"submit\">Sign in</button>\n"
    + "  </form>\n");
 }

 if (oauth2LoginEnabled) {
  sb.append("<h2 class=\"form-signin-heading\">Login with OAuth 2.0</h2>");
  sb.append(createError(loginError, errorMsg));
  sb.append(createLogoutSuccess(logoutSuccess));
  sb.append("<table class=\"table table-striped\">\n");
  for (Map.Entry<String, String> clientAuthenticationUrlToClientName : oauth2AuthenticationUrlToClientName.entrySet()) {
   sb.append(" <tr><td>");
   String url = clientAuthenticationUrlToClientName.getKey();
   sb.append("<a href=\"").append(contextPath).append(url).append("\">");
   String clientName = HtmlUtils.htmlEscape(clientAuthenticationUrlToClientName.getValue());
   sb.append(clientName);
   sb.append("</a>");
   sb.append("</td></tr>\n");
  }
  sb.append("</table>\n");
 }

 if (this.saml2LoginEnabled) {
  sb.append("<h2 class=\"form-signin-heading\">Login with SAML 2.0</h2>");
  sb.append(createError(loginError, errorMsg));
  sb.append(createLogoutSuccess(logoutSuccess));
  sb.append("<table class=\"table table-striped\">\n");
  for (Map.Entry<String, String> relyingPartyUrlToName : saml2AuthenticationUrlToProviderName.entrySet()) {
   sb.append(" <tr><td>");
   String url = relyingPartyUrlToName.getKey();
   sb.append("<a href=\"").append(contextPath).append(url).append("\">");
   String partyName = HtmlUtils.htmlEscape(relyingPartyUrlToName.getValue());
   sb.append(partyName);
   sb.append("</a>");
   sb.append("</td></tr>\n");
  }
  sb.append("</table>\n");
 }
 sb.append("</div>\n");
 sb.append("</body></html>");

 return sb.toString();
}

至此 SpringSecurity 默认表单登录页展示流程源码部分已经全部讲解完毕，会渲染出下面的页面，但是一定要有网的情况，否则样式可能会变化

6.总结

本篇主要讲解 SpringSecurity提供的默认表单登录页 它是如何展示的的流程，包括涉及这一流程中相关的 3个过滤器

1.FilterSecurityInterceptor，
2.ExceptionTranslationFilter ，
3.DefaultLoginPageGeneratingFilter 过滤器，
并且简单介绍了一下 AccessDecisionManager 它主要进行投票来判断该用户是否能够访问相应的 资源
AccessDecisionManager 投票机制我也没有深究 后续我会详细深入一下再展开

以上所述是小编给大家介绍的SpringSecurity 默认表单登录页展示流程源码，希望对大家有所帮助！