结构型-过滤器

使用不同的标准来过滤一组对象。在过滤器链里不断地doFilter()

案例 spring SecurityFilterChain

以下代码省略了许多无关代码。

// FilterChainProxy 类
	private void doFilterInternal(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {
		// 获取Filter
		List<Filter> filters = getFilters(fwRequest);
		VirtualFilterChain vfc = new VirtualFilterChain(fwRequest, chain, filters);
		vfc.doFilter(fwRequest, fwResponse);
	}

	private static class VirtualFilterChain implements FilterChain {
		// SecurityFilterChain
		private final List<Filter> additionalFilters;

		private VirtualFilterChain(FirewalledRequest firewalledRequest,FilterChain chain, List<Filter> additionalFilters) {
			this.additionalFilters = additionalFilters;
		}

		@Override
		public void doFilter(ServletRequest request, ServletResponse response)throws IOException, ServletException {
			if (currentPosition == size) {
			} else {
				Filter nextFilter = additionalFilters.get(currentPosition - 1);
				// 参数 chain 是 this，意味着调用doFilter的时候还是回到这个方法，类似递归。
				nextFilter.doFilter(request, response, this);
			}
		}
	}