Spring Security常用过滤器实例解析

Spring Security常见的15个拦截器

1 . org.springframework.security.web.context.SecurityContextPersistenceFilter

首当其冲的一个过滤器，作用之重要，自不必多言。

SecurityContextPersistenceFilter主要是使用SecurityContextRepository在session中保存或更新一个 SecurityContext，并将SecurityContext给以后的过滤器使用，来为后续filter建立所需的上下文。 SecurityContext中存储了当前用户的认证以及权限信息。

2 . org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter

此过滤器用于集成SecurityContext到Spring异步执行机制中的WebAsyncManager

3 . org.springframework.security.web.header.HeaderWriterFilter

向请求的Header中添加相应的信息,可在http标签内部使用security:headers来控制

4 . org.springframework.security.web.csrf.CsrfFilter

csrf又称跨域请求伪造，SpringSecurity会对所有post请求验证是否包含系统生成的csrf的token信息，

如果不包含，则报错。起到防止csrf攻击的效果。

5. org.springframework.security.web.authentication.logout.LogoutFilter

匹配 URL为/logout的请求，实现用户退出,清除认证信息。

6 . org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter

认证操作全靠这个过滤器，默认匹配URL为/login且必须为POST请求。

7 . org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter

如果没有在配置文件中指定认证页面，则由该过滤器生成一个默认认证页面。

8 . org.springframework.security.web.authentication.ui.DefaultLogoutPageGeneratingFilter

由此过滤器可以生产一个默认的退出登录页面

9 . org.springframework.security.web.authentication.www.BasicAuthenticationFilter

此过滤器会自动解析HTTP请求中头部名字为Authentication，且以Basic开头的头信息。

10 . org.springframework.security.web.savedrequest.RequestCacheAwareFilter

通过HttpSessionRequestCache内部维护了一个RequestCache，用于缓存HttpServletRequest

11 . org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter

针对ServletRequest进行了一次包装，使得request具有更加丰富的API

12 . org.springframework.security.web.authentication.AnonymousAuthenticationFilter

当SecurityContextHolder中认证信息为空,则会创建一个匿名用户存入到SecurityContextHolder中。

spring security为了兼容未登录的访问，也走了一套认证流程，只不过是一个匿名的身份。

13 . org.springframework.security.web.session.SessionManagementFilter

SecurityContextRepository限制同一用户开启多个会话的数量

14 . org.springframework.security.web.access.ExceptionTranslationFilter

异常转换过滤器位于整个springSecurityFilterChain的后方，用来转换整个链路中出现的异常

15 . org.springframework.security.web.access.intercept.FilterSecurityInterceptor

获取所配置资源访问的授权信息，根据SecurityContextHolder中存储的用户信息来决定其是否有权限。

那么，是不是spring security一共就这么多过滤器呢？答案是否定的！随着spring-security.xml配置的添加，还会出现新的过滤器。

那么，是不是spring security每次都会加载这些过滤器呢？答案也是否定的！随着spring-security.xml配置的修改，有些过滤器可能会被去掉。

spring security 过滤器链加载原理

public class DelegatingFilterProxy extends GenericFilterBean {@Nullableprivate String contextAttribute;@Nullableprivate WebApplicationContext webApplicationContext;@Nullableprivate String targetBeanName;private boolean targetFilterLifecycle;@Nullableprivate volatile Filter delegate;//注：这个过滤器才是真正加载的过滤器private final Object delegateMonitor;//注：doFilter才是过滤器的入口，直接从这看！public void doFilter(ServletRequest request, ServletResponse response, FilterChainfilterChain) throws ServletException, IOException {Filter delegateToUse = this.delegate;if (delegateToUse == null) {synchronized(this.delegateMonitor) {delegateToUse = this.delegate;if (delegateToUse == null) {WebApplicationContext wac = this.findWebApplicationContext();if (wac == null) {throw new IllegalStateException('No WebApplicationContext found: noContextLoaderListener or DispatcherServlet registered?');}//第一步：doFilter中最重要的一步，初始化上面私有过滤器属性delegatedelegateToUse = this.initDelegate(wac);}this.delegate = delegateToUse;}}//第三步：执行FilterChainProxy过滤器this.invokeDelegate(delegateToUse, request, response, filterChain);}//第二步：直接看最终加载的过滤器到底是谁protected Filter initDelegate(WebApplicationContext wac) throws ServletException {//debug得知targetBeanName为：springSecurityFilterChainString targetBeanName = this.getTargetBeanName();Assert.state(targetBeanName != null, 'No target bean name set');//debug得知delegate对象为：FilterChainProxyFilter delegate = (Filter)wac.getBean(targetBeanName, Filter.class);if (this.isTargetFilterLifecycle()) {delegate.init(this.getFilterConfig());}return delegate;}protected void invokeDelegate(Filter delegate, ServletRequest request, ServletResponseresponse, FilterChain filterChain) throws ServletException, IOException {delegate.doFilter(request, response, filterChain);}}

第二步debug结果如下：

由此可知， DelegatingFilterProxy通过springSecurityFilterChain这个名称，得到了一个FilterChainProxy过滤器，最终在第三步执行了这个过滤器。

FilterChainProxy

public class FilterChainProxy extends GenericFilterBean {private static final Log logger = LogFactory.getLog(FilterChainProxy.class);private static final String FILTER_APPLIED =FilterChainProxy.class.getName().concat('.APPLIED');private List<SecurityFilterChain> filterChains;private FilterChainProxy.FilterChainValidator filterChainValidator;private HttpFirewall firewall;//咿！？可以通过一个叫SecurityFilterChain的对象实例化出一个FilterChainProxy对象//这FilterChainProxy又是何方神圣？会不会是真正的过滤器链对象呢？先留着这个疑问！public FilterChainProxy(SecurityFilterChain chain) {this(Arrays.asList(chain));}//又是SecurityFilterChain这家伙！嫌疑更大了！public FilterChainProxy(List<SecurityFilterChain> filterChains) {this.filterChainValidator = new FilterChainProxy.NullFilterChainValidator();this.firewall = new StrictHttpFirewall();this.filterChains = filterChains;}//注：直接从doFilter看public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)throws IOException, ServletException {boolean clearContext = request.getAttribute(FILTER_APPLIED) == null;if (clearContext) {try {request.setAttribute(FILTER_APPLIED, Boolean.TRUE);this.doFilterInternal(request, response, chain);} finally {SecurityContextHolder.clearContext();request.removeAttribute(FILTER_APPLIED);}} else {//第一步：具体操作调用下面的doFilterInternal方法了this.doFilterInternal(request, response, chain);}}private void doFilterInternal(ServletRequest request, ServletResponse response, FilterChainchain) throws IOException, ServletException {FirewalledRequest fwRequest =this.firewall.getFirewalledRequest((HttpServletRequest)request);HttpServletResponse fwResponse =this.firewall.getFirewalledResponse((HttpServletResponse)response);//第二步：封装要执行的过滤器链，那么多过滤器就在这里被封装进去了！List<Filter> filters = this.getFilters((HttpServletRequest)fwRequest);if (filters != null && filters.size() != 0) {FilterChainProxy.VirtualFilterChain vfc = newFilterChainProxy.VirtualFilterChain(fwRequest, chain, filters);//第四步：加载过滤器链vfc.doFilter(fwRequest, fwResponse);} else {if (logger.isDebugEnabled()) {logger.debug(UrlUtils.buildRequestUrl(fwRequest) + (filters == null ? ' has nomatching filters' : ' has an empty filter list'));}fwRequest.reset();chain.doFilter(fwRequest, fwResponse);}}private List<Filter> getFilters(HttpServletRequest request) {Iterator var2 = this.filterChains.iterator();//第三步：封装过滤器链到SecurityFilterChain中！SecurityFilterChain chain;do {if (!var2.hasNext()) {return null;}chain = (SecurityFilterChain)var2.next();} while(!chain.matches(request));return chain.getFilters();}}

SecurityFilterChain

最后看SecurityFilterChain，这是个接口，实现类也只有一个，这才是web.xml中配置的过滤器链对象！

public interface SecurityFilterChain { boolean matches(HttpServletRequest request); List<Filter> getFilters();}

public final class DefaultSecurityFilterChain implements SecurityFilterChain { private static final Log logger = LogFactory.getLog(DefaultSecurityFilterChain.class); private final RequestMatcher requestMatcher; private final List<Filter> filters; public DefaultSecurityFilterChain(RequestMatcher requestMatcher, Filter... filters) { this(requestMatcher, Arrays.asList(filters)); } public DefaultSecurityFilterChain(RequestMatcher requestMatcher, List<Filter> filters) { logger.info('Creating filter chain: ' + requestMatcher + ', ' + filters); this.requestMatcher = requestMatcher; this.filters = new ArrayList<>(filters); } public RequestMatcher getRequestMatcher() { return requestMatcher; } public List<Filter> getFilters() { return filters; } public boolean matches(HttpServletRequest request) { return requestMatcher.matches(request); } @Override public String toString() { return '[ ' + requestMatcher + ', ' + filters + ']'; }}

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