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, 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();
}
}
