Spring Security原理学习--核心过滤器Filter

忘是亡心i 2022-04-18 00:44 230阅读 0赞

首先Spring Security的认证功能是依赖Filter实现的，当然在认证功能基础上还提供了一些安全的验证等都是依赖Filter来实现完成的，如下截图Spring Security提供了13个功能Filter，并且是按照如下顺序依次执行的。当然配合Spring web的Filter注入实现，Spring Security提供了另外一个Filter的实现类FilterChainProxy，其对外包装了以下13个Filter，其实13个Filter是在接口SecurityFilterChain的实现类DefaultSecurityFilterChain中通过List保存的。  
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接下来我们依次介绍一下这个13个Filter。

### 1、WebAsyncManagerIntegrationFilter ###

接下来我们依次介绍一下这个13个Filter。

1、WebAsyncManagerIntegrationFilter  
public final class WebAsyncManagerIntegrationFilter extends OncePerRequestFilter \{  
    private static final Object CALLABLE\_INTERCEPTOR\_KEY = new Object();  
   
    @Override  
    protected void doFilterInternal(HttpServletRequest request,  
            HttpServletResponse response, FilterChain filterChain)  
            throws ServletException, IOException \{  
        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);  
   
        SecurityContextCallableProcessingInterceptor securityProcessingInterceptor = (SecurityContextCallableProcessingInterceptor) asyncManager  
                .getCallableInterceptor(CALLABLE\_INTERCEPTOR\_KEY);  
        if (securityProcessingInterceptor == null) \{  
            asyncManager.registerCallableInterceptor(CALLABLE\_INTERCEPTOR\_KEY,  
                    new SecurityContextCallableProcessingInterceptor());  
        \}  
   
        filterChain.doFilter(request, response);  
    \}  
\}  
根据请求封装获取WebAsyncManager  
从WebAsyncManager获取/注册SecurityContextCallableProcessingInterceptor  
2、SecurityContextPersistenceFilter  
两个主要职责：请求来临时，创建SecurityContext安全上下文信息，请求结束时清空SecurityContextHolder。

public class SecurityContextPersistenceFilter extends GenericFilterBean \{  
   
    static final String FILTER\_APPLIED = "\_\_spring\_security\_scpf\_applied";  
   
    private SecurityContextRepository repo;  
   
    private boolean forceEagerSessionCreation = false;  
   
    public SecurityContextPersistenceFilter() \{  
        this(new HttpSessionSecurityContextRepository());  
    \}  
   
    public SecurityContextPersistenceFilter(SecurityContextRepository repo) \{  
        this.repo = repo;  
    \}  
   
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)  
            throws IOException, ServletException \{  
        HttpServletRequest request = (HttpServletRequest) req;  
        HttpServletResponse response = (HttpServletResponse) res;  
          
        //判断是否已经处理过  
        if (request.getAttribute(FILTER\_APPLIED) != null) \{  
            // ensure that filter is only applied once per request  
            chain.doFilter(request, response);  
            return;  
        \}  
   
        final boolean debug = logger.isDebugEnabled();  
   
        request.setAttribute(FILTER\_APPLIED, Boolean.TRUE);  
   
        if (forceEagerSessionCreation) \{  
            HttpSession session = request.getSession();  
   
            if (debug && session.isNew()) \{  
                logger.debug("Eagerly created session: " + session.getId());  
            \}  
        \}  
   
        HttpRequestResponseHolder holder = new HttpRequestResponseHolder(request,  
                response);  
        //获取SecurityContext  
        SecurityContext contextBeforeChainExecution = repo.loadContext(holder);  
   
        try \{  
            SecurityContextHolder.setContext(contextBeforeChainExecution);  
   
            chain.doFilter(holder.getRequest(), holder.getResponse());  
   
        \}  
        finally \{  
            //结束后清理SecurityContext  
            SecurityContext contextAfterChainExecution = SecurityContextHolder  
                    .getContext();  
            // Crucial removal of SecurityContextHolder contents - do this before anything  
            // else.  
            SecurityContextHolder.clearContext();  
            repo.saveContext(contextAfterChainExecution, holder.getRequest(),  
                    holder.getResponse());  
            request.removeAttribute(FILTER\_APPLIED);  
   
            if (debug) \{  
                logger.debug("SecurityContextHolder now cleared, as request processing completed");  
            \}  
        \}  
    \}  
   
    public void setForceEagerSessionCreation(boolean forceEagerSessionCreation) \{  
        this.forceEagerSessionCreation = forceEagerSessionCreation;  
    \}  
\}  
3、HeaderWriterFilter  
用来给http响应添加一些Header,比如X-Frame-Options, X-XSS-Protection\*，X-Content-Type-Options.

public class HeaderWriterFilter extends OncePerRequestFilter \{  
   
    /\*\*  
     \* Collection of \{@link HeaderWriter\} instances to write out the headers to the  
     \* response.  
     \*/  
    private final List<HeaderWriter> headerWriters;  
   
    /\*\*  
     \* Creates a new instance.  
     \*  
     \* @param headerWriters the \{@link HeaderWriter\} instances to write out headers to the  
     \* \{@link HttpServletResponse\}.  
     \*/  
    public HeaderWriterFilter(List<HeaderWriter> headerWriters) \{  
        Assert.notEmpty(headerWriters, "headerWriters cannot be null or empty");  
        this.headerWriters = headerWriters;  
    \}  
   
    @Override  
    protected void doFilterInternal(HttpServletRequest request,  
            HttpServletResponse response, FilterChain filterChain)  
                    throws ServletException, IOException \{  
   
        HeaderWriterResponse headerWriterResponse = new HeaderWriterResponse(request,  
                response, this.headerWriters);  
        try \{  
            filterChain.doFilter(request, headerWriterResponse);  
        \}  
        finally \{  
            headerWriterResponse.writeHeaders();  
        \}  
    \}  
   
    static class HeaderWriterResponse extends OnCommittedResponseWrapper \{  
        private final HttpServletRequest request;  
        private final List<HeaderWriter> headerWriters;  
   
        HeaderWriterResponse(HttpServletRequest request, HttpServletResponse response,  
                List<HeaderWriter> headerWriters) \{  
            super(response);  
            this.request = request;  
            this.headerWriters = headerWriters;  
        \}  
   
        /\*  
         \* (non-Javadoc)  
         \*  
         \* @see org.springframework.security.web.util.OnCommittedResponseWrapper\#  
         \* onResponseCommitted()  
         \*/  
        @Override  
        protected void onResponseCommitted() \{  
            writeHeaders();  
            this.disableOnResponseCommitted();  
        \}  
   
        protected void writeHeaders() \{  
            if (isDisableOnResponseCommitted()) \{  
                return;  
            \}  
            for (HeaderWriter headerWriter : this.headerWriters) \{  
                headerWriter.writeHeaders(this.request, getHttpResponse());  
            \}  
        \}  
   
        private HttpServletResponse getHttpResponse() \{  
            return (HttpServletResponse) getResponse();  
        \}  
    \}  
\}  
4、LogoutFilter  
退出拦截器，退出的简单操作就是删除Session，根据Spring Security初始化配置的退出地址来匹配请求。

public class LogoutFilter extends GenericFilterBean \{  
   
    // ~ Instance fields  
    // ================================================================================================  
   
    private RequestMatcher logoutRequestMatcher;  
   
    private final List<LogoutHandler> handlers;  
    private final LogoutSuccessHandler logoutSuccessHandler;  
   
    // ~ Constructors  
    // ===================================================================================================  
   
    /\*\*  
     \* Constructor which takes a <tt>LogoutSuccessHandler</tt> instance to determine the  
     \* target destination after logging out. The list of <tt>LogoutHandler</tt>s are  
     \* intended to perform the actual logout functionality (such as clearing the security  
     \* context, invalidating the session, etc.).  
     \*/  
    public LogoutFilter(LogoutSuccessHandler logoutSuccessHandler,  
            LogoutHandler... handlers) \{  
        Assert.notEmpty(handlers, "LogoutHandlers are required");  
        this.handlers = Arrays.asList(handlers);  
        Assert.notNull(logoutSuccessHandler, "logoutSuccessHandler cannot be null");  
        this.logoutSuccessHandler = logoutSuccessHandler;  
        setFilterProcessesUrl("/logout");  
    \}  
   
    public LogoutFilter(String logoutSuccessUrl, LogoutHandler... handlers) \{  
        Assert.notEmpty(handlers, "LogoutHandlers are required");  
        this.handlers = Arrays.asList(handlers);  
        Assert.isTrue(  
                !StringUtils.hasLength(logoutSuccessUrl)  
                        || UrlUtils.isValidRedirectUrl(logoutSuccessUrl),  
                logoutSuccessUrl + " isn't a valid redirect URL");  
        SimpleUrlLogoutSuccessHandler urlLogoutSuccessHandler = new SimpleUrlLogoutSuccessHandler();  
        if (StringUtils.hasText(logoutSuccessUrl)) \{  
            urlLogoutSuccessHandler.setDefaultTargetUrl(logoutSuccessUrl);  
        \}  
        logoutSuccessHandler = urlLogoutSuccessHandler;  
        setFilterProcessesUrl("/logout");  
    \}  
   
    // ~ Methods  
    // ========================================================================================================  
   
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)  
            throws IOException, ServletException \{  
        HttpServletRequest request = (HttpServletRequest) req;  
        HttpServletResponse response = (HttpServletResponse) res;  
        //判断是不是退出请求  
        if (requiresLogout(request, response)) \{  
            Authentication auth = SecurityContextHolder.getContext().getAuthentication();  
   
            if (logger.isDebugEnabled()) \{  
                logger.debug("Logging out user '" + auth  
                        + "' and transferring to logout destination");  
            \}  
   
            for (LogoutHandler handler : handlers) \{  
                //在logoutHandler中进行删除session操作  
                handler.logout(request, response, auth);  
            \}  
   
            logoutSuccessHandler.onLogoutSuccess(request, response, auth);  
   
            return;  
        \}  
   
        chain.doFilter(request, response);  
    \}  
   
    /\*\*  
     \* Allow subclasses to modify when a logout should take place.  
     \*  
     \* @param request the request  
     \* @param response the response  
     \*  
     \* @return <code>true</code> if logout should occur, <code>false</code> otherwise  
     \*/  
    protected boolean requiresLogout(HttpServletRequest request,  
            HttpServletResponse response) \{  
        return logoutRequestMatcher.matches(request);  
    \}  
   
    public void setLogoutRequestMatcher(RequestMatcher logoutRequestMatcher) \{  
        Assert.notNull(logoutRequestMatcher, "logoutRequestMatcher cannot be null");  
        this.logoutRequestMatcher = logoutRequestMatcher;  
    \}  
   
    public void setFilterProcessesUrl(String filterProcessesUrl) \{  
        this.logoutRequestMatcher = new AntPathRequestMatcher(filterProcessesUrl);  
    \}  
\}  
当判断请求是退出时，会调用LogoutHandler的logout删除session，具体实现在SecurityContextLogoutHandler的logout方法中。

public void logout(HttpServletRequest request, HttpServletResponse response,  
            Authentication authentication) \{  
        Assert.notNull(request, "HttpServletRequest required");  
        if (invalidateHttpSession) \{  
            //设置session无效  
            HttpSession session = request.getSession(false);  
            if (session != null) \{  
                logger.debug("Invalidating session: " + session.getId());  
                session.invalidate();  
            \}  
        \}  
   
        if (clearAuthentication) \{  
            SecurityContext context = SecurityContextHolder.getContext();  
            context.setAuthentication(null);  
        \}  
        //清理信息  
        SecurityContextHolder.clearContext();  
    \}  
5、UsernamePasswordAuthenticationFilter  
        用户名和密码校验Filter，是特别重要的一个Filter，我们会在用户登录验证博客中专门进行分析学习一下，当然这个Filter只会对配置的登录请求/login进行业务处理，其他请求不做任何业务处理，其处理逻辑在父类AbstractAuthenticationProcessingFilter中。

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)  
            throws IOException, ServletException \{  
   
        HttpServletRequest request = (HttpServletRequest) req;  
        HttpServletResponse response = (HttpServletResponse) res;  
        //首先判断是不是登录请求，不是登录请求则直接跳过  
        if (!requiresAuthentication(request, response)) \{  
            chain.doFilter(request, response);  
   
            return;  
        \}  
        //是登录请求进行校验工作  
        //省略部分代码  
        authResult = attemptAuthentication(request, response);  
        //省略部分代码  
          
    \}  
6、DefaultLoginPageGeneratingFilter  
         当是登录地址请求，登录失败请求或者登出请求则跳转到登录页面。

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);  
        //登录请求，登录错误请求或者登出请求则返回登录页面  
        if (isLoginUrlRequest(request) || loginError || logoutSuccess) \{  
            String loginPageHtml = generateLoginPageHtml(request, loginError,  
                    logoutSuccess);  
            response.setContentType("text/html;charset=UTF-8");  
            response.setContentLength(loginPageHtml.length());  
            response.getWriter().write(loginPageHtml);  
   
            return;  
        \}  
   
        chain.doFilter(request, response);  
    \}  
7、BasicAuthenticationFilter  
        处理BASIC authentication认证方式，简单理解和UsernamePasswordAuthenticationFilter类似，不过UsernamePasswordAuthenticationFilter是通过表单提交的，而Authorization认证方式是将用户名密码数据添加到请求header中罢了。

@Override  
    protected void doFilterInternal(HttpServletRequest request,  
            HttpServletResponse response, FilterChain chain)  
                    throws IOException, ServletException \{  
        final boolean debug = this.logger.isDebugEnabled();  
        //请求头中获取Authorization  
        String header = request.getHeader("Authorization");  
        //如果不存在或者不是以Basic开头直接跳过处理  
        if (header == null || !header.startsWith("Basic ")) \{  
            chain.doFilter(request, response);  
            return;  
        \}  
        //从header中获取相关用户名密码数据进行验证  
        try \{  
            String\[\] tokens = extractAndDecodeHeader(header, request);  
            assert tokens.length == 2;  
   
            String username = tokens\[0\];  
   
            if (debug) \{  
                this.logger  
                        .debug("Basic Authentication Authorization header found for user '"  
                                + username + "'");  
            \}  
   
            if (authenticationIsRequired(username)) \{  
                UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(  
                        username, tokens\[1\]);  
                authRequest.setDetails(  
                        this.authenticationDetailsSource.buildDetails(request));  
                Authentication authResult = this.authenticationManager  
                        .authenticate(authRequest);  
   
                if (debug) \{  
                    this.logger.debug("Authentication success: " + authResult);  
                \}  
   
                SecurityContextHolder.getContext().setAuthentication(authResult);  
   
                this.rememberMeServices.loginSuccess(request, response, authResult);  
   
                onSuccessfulAuthentication(request, response, authResult);  
            \}  
   
        \}  
        catch (AuthenticationException failed) \{  
            SecurityContextHolder.clearContext();  
   
            if (debug) \{  
                this.logger.debug("Authentication request for failed: " + failed);  
            \}  
   
            this.rememberMeServices.loginFail(request, response);  
   
            onUnsuccessfulAuthentication(request, response, failed);  
   
            if (this.ignoreFailure) \{  
                chain.doFilter(request, response);  
            \}  
            else \{  
                this.authenticationEntryPoint.commence(request, response, failed);  
            \}  
   
            return;  
        \}  
   
        chain.doFilter(request, response);  
    \}  
8、RequestCacheAwareFilter   
内部维护了一个RequestCache，用于缓存request请求

public class RequestCacheAwareFilter extends GenericFilterBean \{  
   
    private RequestCache requestCache;  
   
    public RequestCacheAwareFilter() \{  
        this(new HttpSessionRequestCache());  
    \}  
   
    public RequestCacheAwareFilter(RequestCache requestCache) \{  
        Assert.notNull(requestCache, "requestCache cannot be null");  
        this.requestCache = requestCache;  
    \}  
   
    public void doFilter(ServletRequest request, ServletResponse response,  
            FilterChain chain) throws IOException, ServletException \{  
   
        HttpServletRequest wrappedSavedRequest = requestCache.getMatchingRequest(  
                (HttpServletRequest) request, (HttpServletResponse) response);  
   
        chain.doFilter(wrappedSavedRequest == null ? request : wrappedSavedRequest,  
                response);  
    \}  
   
\}  
9、SecurityContextHolderAwareRequestFilter   
        此过滤器对ServletRequest进行了一次包装，使得request具有更加丰富的API

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)  
            throws IOException, ServletException \{  
        chain.doFilter(this.requestFactory.create((HttpServletRequest) req,  
                (HttpServletResponse) res), res);  
    \}  
10、AnonymousAuthenticationFilter  
           匿名身份过滤器，这个过滤器个人认为很重要，需要将它与UsernamePasswordAuthenticationFilter 放在一起比较理解，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。

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)  
            throws IOException, ServletException \{  
   
        if (SecurityContextHolder.getContext().getAuthentication() == null) \{  
            //创建一个匿名身份  
            SecurityContextHolder.getContext().setAuthentication(  
                    createAuthentication((HttpServletRequest) req));  
   
            if (logger.isDebugEnabled()) \{  
                logger.debug("Populated SecurityContextHolder with anonymous token: '"  
                        + SecurityContextHolder.getContext().getAuthentication() + "'");  
            \}  
        \}  
        else \{  
            if (logger.isDebugEnabled()) \{  
                logger.debug("SecurityContextHolder not populated with anonymous token, as it already contained: '"  
                        + SecurityContextHolder.getContext().getAuthentication() + "'");  
            \}  
        \}  
   
        chain.doFilter(req, res);  
    \}  
   
    protected Authentication createAuthentication(HttpServletRequest request) \{  
        AnonymousAuthenticationToken auth = new AnonymousAuthenticationToken(key,  
                principal, authorities);  
        auth.setDetails(authenticationDetailsSource.buildDetails(request));  
   
        return auth;  
    \}  
11、SessionManagementFilter  
           和session相关的过滤器，内部维护了一个SessionAuthenticationStrategy，两者组合使用，常用来防止session-fixation protection attack，以及限制同一用户开启多个会话的数量

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)  
            throws IOException, ServletException \{  
        HttpServletRequest request = (HttpServletRequest) req;  
        HttpServletResponse response = (HttpServletResponse) res;  
   
        if (request.getAttribute(FILTER\_APPLIED) != null) \{  
            chain.doFilter(request, response);  
            return;  
        \}  
   
        request.setAttribute(FILTER\_APPLIED, Boolean.TRUE);  
   
        if (!securityContextRepository.containsContext(request)) \{  
            Authentication authentication = SecurityContextHolder.getContext()  
                    .getAuthentication();  
   
            if (authentication != null && !trustResolver.isAnonymous(authentication)) \{  
                // The user has been authenticated during the current request, so call the  
                // session strategy  
                try \{  
                    sessionAuthenticationStrategy.onAuthentication(authentication,  
                            request, response);  
                \}  
                catch (SessionAuthenticationException e) \{  
                    // The session strategy can reject the authentication  
                    logger.debug(  
                            "SessionAuthenticationStrategy rejected the authentication object",  
                            e);  
                    SecurityContextHolder.clearContext();  
                    failureHandler.onAuthenticationFailure(request, response, e);  
   
                    return;  
                \}  
                // Eagerly save the security context to make it available for any possible  
                // re-entrant  
                // requests which may occur before the current request completes.  
                // SEC-1396.  
                securityContextRepository.saveContext(SecurityContextHolder.getContext(),  
                        request, response);  
            \}  
            else \{  
                // No security context or authentication present. Check for a session  
                // timeout  
                if (request.getRequestedSessionId() != null  
                        && !request.isRequestedSessionIdValid()) \{  
                    if (logger.isDebugEnabled()) \{  
                        logger.debug("Requested session ID "  
                                + request.getRequestedSessionId() + " is invalid.");  
                    \}  
   
                    if (invalidSessionStrategy != null) \{  
                        invalidSessionStrategy  
                                .onInvalidSessionDetected(request, response);  
                        return;  
                    \}  
                \}  
            \}  
        \}  
   
        chain.doFilter(request, response);  
    \}  
12、ExceptionTranslationFilter  
        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，将其转化，顾名思义，转化以意味本身并不处理。一般其只处理两大类异常：AccessDeniedException访问异常和AuthenticationException认证异常。这个过滤器非常重要，因为它将Java中的异常和HTTP的响应连接在了一起，这样在处理异常时，我们不用考虑密码错误该跳到什么页面，账号锁定该如何，只需要关注自己的业务逻辑，抛出相应的异常便可。如果该过滤器检测到AuthenticationException，则将会交给内部的AuthenticationEntryPoint去处理，如果检测到AccessDeniedException，需要先判断当前用户是不是匿名用户，如果是匿名访问，则和前面一样运行AuthenticationEntryPoint，否则会委托给AccessDeniedHandler去处理，而AccessDeniedHandler的默认实现，是AccessDeniedHandlerImpl。所以ExceptionTranslationFilter内部的AuthenticationEntryPoint是至关重要的，顾名思义：认证的入口点。

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;  
        \}  
        //捕捉一些异常处理，身份校验判断错误会抛出异常，由这里处理  
        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) \{  
                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);  
            \}  
        \}  
    \}  
13、FilterSecurityInterceptor  
        个人理解任务这个拦截器是Spring Security中最重要的，首先这个拦截器就是进行角色相关的处理，也是登录结果是否成功最后一个判断的拦截器，针对不需要认证和需要认证的请求会进行不同的验证处理，同样在登录博客中会对其做的功能进行详细的说明。

public void doFilter(ServletRequest request, ServletResponse response,  
            FilterChain chain) throws IOException, ServletException \{  
        FilterInvocation fi = new FilterInvocation(request, response, chain);  
   
        invoke(fi);  
    \}  
   
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) \{  
                fi.getRequest().setAttribute(FILTER\_APPLIED, Boolean.TRUE);  
            \}  
            //在执行请求调用之前进行验证处理  
            InterceptorStatusToken token = super.beforeInvocation(fi);  
   
            try \{  
                fi.getChain().doFilter(fi.getRequest(), fi.getResponse());  
            \}  
            finally \{  
                super.finallyInvocation(token);  
            \}  
   
            super.afterInvocation(token, null);  
        \}  
    \}

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