标准的RABC, 权限需要支持动态配置，spring security默认是在代码里约定好权限，真实的业务场景通常需要可以支持动态配置角色访问权限，即在运行时去配置url对应的访问角色。
基于spring security，如何实现这个需求呢？
最简单的方法就是自定义一个Filter去完成权限判断，但这脱离了spring security框架，如何基于spring security优雅的实现呢？
spring security 授权回顾spring security 通过FilterChainProxy作为注册到web的filter，FilterChainProxy里面一次包含了内置的多个过滤器，我们首先需要了解spring security内置的各种filter：
Alias Filter Class Namespace Element or AttributeCHANNEL_FILTER ChannelProcessingFilter http/intercept-url@requires-channel
SECURITY_CONTEXT_FILTER SecurityContextPersistenceFilter http
CONCURRENT_SESSION_FILTER ConcurrentSessionFilter session-management/concurrency-control
HEADERS_FILTER HeaderWriterFilter http/headers
CSRF_FILTER CsrfFilter http/csrf
LOGOUT_FILTER LogoutFilter http/logout
X509_FILTER X509AuthenticationFilter http/x509
PRE_AUTH_FILTER AbstractPreAuthenticatedProcessingFilter Subclasses N/A
CAS_FILTER CasAuthenticationFilter N/A
FORM_LOGIN_FILTER UsernamePasswordAuthenticationFilter http/form-login
BASIC_AUTH_FILTER BasicAuthenticationFilter http/http-basic
SERVLET_API_SUPPORT_FILTER SecurityContextHolderAwareRequestFilter http/@servlet-api-provision
JAAS_API_SUPPORT_FILTER JaasApiIntegrationFilter http/@jaas-api-provision
REMEMBER_ME_FILTER RememberMeAuthenticationFilter http/remember-me
ANONYMOUS_FILTER AnonymousAuthenticationFilter http/anonymous
SESSION_MANAGEMENT_FILTER SessionManagementFilter session-management
EXCEPTION_TRANSLATION_FILTER ExceptionTranslationFilter http
FILTER_SECURITY_INTERCEPTOR FilterSecurityInterceptor http
SWITCH_USER_FILTER SwitchUserFilter N/A
最重要的是FilterSecurityInterceptor，该过滤器实现了主要的鉴权逻辑，最核心的代码在这里：
protected InterceptorStatusToken beforeInvocation(Object object) { // 获取访问URL所需权限 Collection<ConfigAttribute> attributes = this.obtainSecurityMetadataSource() .getAttributes(object); Authentication authenticated = authenticateIfRequired(); // 通过accessDecisionManager鉴权 try { this.accessDecisionManager.decide(authenticated, object, attributes); } catch (AccessDeniedException accessDeniedException) { publishEvent(new AuthorizationFailureEvent(object, attributes, authenticated, accessDeniedException)); throw accessDeniedException; } if (debug) { logger.debug("Authorization successful"); } if (publishAuthorizationSuccess) { publishEvent(new AuthorizedEvent(object, attributes, authenticated)); } // Attempt to run as a different user Authentication runAs = this.runAsManager.buildRunAs(authenticated, object, attributes); if (runAs == null) { if (debug) { logger.debug("RunAsManager did not change Authentication object"); } // no further work post-invocation return new InterceptorStatusToken(SecurityContextHolder.getContext(), false, attributes, object); } else { if (debug) { logger.debug("Switching to RunAs Authentication: " + runAs); } SecurityContext origCtx = SecurityContextHolder.getContext(); SecurityContextHolder.setContext(SecurityContextHolder.createEmptyContext()); SecurityContextHolder.getContext().setAuthentication(runAs); // need to revert to token.Authenticated post-invocation return new InterceptorStatusToken(origCtx, true, attributes, object); } }从上面可以看出，要实现动态鉴权，可以从两方面着手：
自定义SecurityMetadataSource，实现从数据库加载ConfigAttribute
另外就是可以自定义accessDecisionManager，官方的UnanimousBased其实足够使用，并且他是基于AccessDecisionVoter来实现权限认证的，因此我们只需要自定义一个AccessDecisionVoter就可以了
下面来看分别如何实现。
自定义AccessDecisionManager官方的三个AccessDecisionManager都是基于AccessDecisionVoter来实现权限认证的，因此我们只需要自定义一个AccessDecisionVoter就可以了。
自定义主要是实现AccessDecisionVoter接口，我们可以仿照官方的RoleVoter实现一个：