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, FilterChain
                                  chain) 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 = new
            FilterChainProxy.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 no matching 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();
  }
}