Spring Cloud GateWay 源碼解析實戰 - FilteringWebHandler(更新ing)

package org.springframework.cloud.gateway.handler;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import reactor.core.publisher.Mono;

import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.cloud.gateway.filter.OrderedGatewayFilter;
import org.springframework.cloud.gateway.filter.factory.GatewayFilterFactory;
import org.springframework.cloud.gateway.route.Route;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebHandler;

import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR;

/**
 * WebHandler that delegates to a chain of {@link GlobalFilter} instances and
 * {@link GatewayFilterFactory} instances then to the target {@link WebHandler}.
 *
 * @author Rossen Stoyanchev
 * @author Spencer Gibb
 * @since 0.1
 */
public class FilteringWebHandler implements WebHandler {

    protected static final Log logger = LogFactory.getLog(FilteringWebHandler.class);

    private final List<GatewayFilter> globalFilters;

    public FilteringWebHandler(List<GlobalFilter> globalFilters) {
        this.globalFilters = loadFilters(globalFilters);
    }

    private static List<GatewayFilter> loadFilters(List<GlobalFilter> filters) {
        return filters.stream().map(filter -> {
            GatewayFilterAdapter gatewayFilter = new GatewayFilterAdapter(filter);
            if (filter instanceof Ordered) {
                int order = ((Ordered) filter).getOrder();
                return new OrderedGatewayFilter(gatewayFilter, order);
            }
            return gatewayFilter;
        }).collect(Collectors.toList());
    }

    /*
     * TODO: relocate @EventListener(RefreshRoutesEvent.class) void handleRefresh() {
     * this.combinedFiltersForRoute.clear();
     */

    @Override
    public Mono<Void> handle(ServerWebExchange exchange) {
        Route route = exchange.getRequiredAttribute(GATEWAY_ROUTE_ATTR);
        List<GatewayFilter> gatewayFilters = route.getFilters();

        List<GatewayFilter> combined = new ArrayList<>(this.globalFilters);
        combined.addAll(gatewayFilters);
        // TODO: needed or cached?
        AnnotationAwareOrderComparator.sort(combined);

        if (logger.isDebugEnabled()) {
            logger.debug("Sorted gatewayFilterFactories: " + combined);
        }

        return new DefaultGatewayFilterChain(combined).filter(exchange);
    }

    private static class DefaultGatewayFilterChain implements GatewayFilterChain {

        private final int index;

        private final List<GatewayFilter> filters;

        DefaultGatewayFilterChain(List<GatewayFilter> filters) {
            this.filters = filters;
            this.index = 0;
        }

        private DefaultGatewayFilterChain(DefaultGatewayFilterChain parent, int index) {
            this.filters = parent.getFilters();
            this.index = index;
        }

        public List<GatewayFilter> getFilters() {
            return filters;
        }

        @Override
        public Mono<Void> filter(ServerWebExchange exchange) {
            return Mono.defer(() -> {
                if (this.index < filters.size()) {
                    GatewayFilter filter = filters.get(this.index);
                    DefaultGatewayFilterChain chain = new DefaultGatewayFilterChain(this,
                            this.index + 1);
                    return filter.filter(exchange, chain);
                }
                else {
                    return Mono.empty(); // complete
                }
            });
        }

    }

    private static class GatewayFilterAdapter implements GatewayFilter {

        private final GlobalFilter delegate;

        GatewayFilterAdapter(GlobalFilter delegate) {
            this.delegate = delegate;
        }

        @Override
        public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
            return this.delegate.filter(exchange, chain);
        }

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("GatewayFilterAdapter{");
            sb.append("delegate=").append(delegate);
            sb.append('}');
            return sb.toString();
        }

    }

}