责任链

• Chain of Responsibility

• interface Filter {
      boolean doFilter(Msg m);
  }
  class HTMLFilter implements Filter {}
  class FilterChain implements Filter{
      List<Filter> filters = new ArrayList<>();
      public boolean doFilter(Msg msg){
          for (Filter f : filters) {
              if (!f.doFilter(msg)) {
                  return false;
              }
          }
          return true;
      }
      public FilterChain add(Filter f) {
          filters.add(f);
          return this;
      }
  }
  FilterChain fc = new FilterChain();
  FilterChain fc2 = new FilterChain();
  Filter f = new Filter();
  fc.add(f).add(fc2);
   
  # ServletFilter
  Filter1 implements Filter {
      void doFilter(req, resp, chain) {
          chain.doFilter(req, resp);
      }
  }
  FilterChain implements Filter {
      List<Filter> filters;
      int curIndex = 0;
      void doFilter(req, resp){
          curIndex++;
          if (curIndex < filters.size()) {
              filters[curIndex].doFilter(req, resp, this);
          }
      }
  }