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聊聊spring cloud gateway的GlobalFilter

go4it
 go4it
发布于 06/08 13:38
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本文主要研究一下spring cloud gateway的GlobalFilter

GatewayAutoConfiguration

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@Configuration
@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)
@EnableConfigurationProperties
@AutoConfigureBefore(HttpHandlerAutoConfiguration.class)
@AutoConfigureAfter({GatewayLoadBalancerClientAutoConfiguration.class, GatewayClassPathWarningAutoConfiguration.class})
@ConditionalOnClass(DispatcherHandler.class)
public class GatewayAutoConfiguration {
	//......
	@Bean
	public FilteringWebHandler filteringWebHandler(List<GlobalFilter> globalFilters) {
		return new FilteringWebHandler(globalFilters);
	}

	@Bean
	public RoutePredicateHandlerMapping routePredicateHandlerMapping(FilteringWebHandler webHandler,
																	   RouteLocator routeLocator) {
		return new RoutePredicateHandlerMapping(webHandler, routeLocator);
	}
	//......
}
  • 这里将globalFilters(NettyWriteResponseFilter、ForwardPathFilter、RouteToRequestUrlFilter、LoadBalancerClientFilter、AdaptCachedBodyGlobalFilter、WebsocketRoutingFilter、NettyRoutingFilter、ForwardRoutingFilter)作为构造器参数创建了FilteringWebHandler
  • 而依据FilteringWebHandler和RouteLocator创建了RoutePredicateHandlerMapping,这里的RouteLocator是CachingRouteLocator

FilteringWebHandler

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/handler/FilteringWebHandler.java

/**
 * 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);

		logger.debug("Sorted gatewayFilterFactories: "+ combined);

		return new DefaultGatewayFilterChain(combined).filter(exchange);
	}
	//......
}
  • 这里在构造器里头调用loadFilters方法把List<GlobalFilter>转换为List<GatewayFilter>
  • 之后的handle方法,把选定的route的gatewayFilters与转换后的gatewayFilters合并,然后重新排序
  • 之后使用合并后的gatewayFilters创建DefaultGatewayFilterChain,挨个filter下去

GatewayFilterAdapter

	private static class GatewayFilterAdapter implements GatewayFilter {

		private final GlobalFilter delegate;

		public 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();
		}
	}

这里将GlobalFilter适配为GatewayFilter,最后调用filter方法

DefaultGatewayFilterChain

	private static class DefaultGatewayFilterChain implements GatewayFilterChain {

		private final int index;
		private final List<GatewayFilter> filters;

		public 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
				}
			});
		}
	}

这里使用了责任链模式,里头filter方法,挨个遍历执行,传入的chain包含了当前的index,用于控制跳出责任链

RoutePredicateHandlerMapping

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/handler/RoutePredicateHandlerMapping.java

public class RoutePredicateHandlerMapping extends AbstractHandlerMapping {

	private final FilteringWebHandler webHandler;
	private final RouteLocator routeLocator;

	public RoutePredicateHandlerMapping(FilteringWebHandler webHandler, RouteLocator routeLocator) {
		this.webHandler = webHandler;
		this.routeLocator = routeLocator;

		setOrder(1);
	}

	@Override
	protected Mono<?> getHandlerInternal(ServerWebExchange exchange) {
		exchange.getAttributes().put(GATEWAY_HANDLER_MAPPER_ATTR, getClass().getSimpleName());

		return lookupRoute(exchange)
				// .log("route-predicate-handler-mapping", Level.FINER) //name this
				.flatMap((Function<Route, Mono<?>>) r -> {
					exchange.getAttributes().remove(GATEWAY_PREDICATE_ROUTE_ATTR);
					if (logger.isDebugEnabled()) {
						logger.debug("Mapping [" + getExchangeDesc(exchange) + "] to " + r);
					}

					exchange.getAttributes().put(GATEWAY_ROUTE_ATTR, r);
					return Mono.just(webHandler);
				}).switchIfEmpty(Mono.empty().then(Mono.fromRunnable(() -> {
					exchange.getAttributes().remove(GATEWAY_PREDICATE_ROUTE_ATTR);
					if (logger.isTraceEnabled()) {
						logger.trace("No RouteDefinition found for [" + getExchangeDesc(exchange) + "]");
					}
				})));
	}

	@Override
	protected CorsConfiguration getCorsConfiguration(Object handler, ServerWebExchange exchange) {
		//TODO: support cors configuration via global properties and
		// properties on a route see gh-229
		// see RequestMappingHandlerMapping.initCorsConfiguration()
		// also see https://github.com/spring-projects/spring-framework/blob/master/spring-web/src/test/java/org/springframework/web/cors/reactive/CorsWebFilterTests.java
		return super.getCorsConfiguration(handler, exchange);
	}
	//......
}

这个RoutePredicateHandlerMapping主要是实现了父类的getHandlerInternal

DispatcherHandler

spring-webflux-5.0.6.RELEASE-sources.jar!/org/springframework/web/reactive/DispatcherHandler.java

/**
 * Central dispatcher for HTTP request handlers/controllers. Dispatches to
 * registered handlers for processing a request, providing convenient mapping
 * facilities.
 *
 * <p>{@code DispatcherHandler} discovers the delegate components it needs from
 * Spring configuration. It detects the following in the application context:
 * <ul>
 * <li>{@link HandlerMapping} -- map requests to handler objects
 * <li>{@link HandlerAdapter} -- for using any handler interface
 * <li>{@link HandlerResultHandler} -- process handler return values
 * </ul>
 *
 * <p>{@code DispatcherHandler} is also designed to be a Spring bean itself and
 * implements {@link ApplicationContextAware} for access to the context it runs
 * in. If {@code DispatcherHandler} is declared with the bean name "webHandler"
 * it is discovered by {@link WebHttpHandlerBuilder#applicationContext} which
 * creates a processing chain together with {@code WebFilter},
 * {@code WebExceptionHandler} and others.
 *
 * <p>A {@code DispatcherHandler} bean declaration is included in
 * {@link org.springframework.web.reactive.config.EnableWebFlux @EnableWebFlux}
 * configuration.
 *
 * @author Rossen Stoyanchev
 * @author Sebastien Deleuze
 * @author Juergen Hoeller
 * @since 5.0
 * @see WebHttpHandlerBuilder#applicationContext(ApplicationContext)
 */
public class DispatcherHandler implements WebHandler, ApplicationContextAware {

	@SuppressWarnings("ThrowableInstanceNeverThrown")
	private static final Exception HANDLER_NOT_FOUND_EXCEPTION =
			new ResponseStatusException(HttpStatus.NOT_FOUND, "No matching handler");


	private static final Log logger = LogFactory.getLog(DispatcherHandler.class);

	@Nullable
	private List<HandlerMapping> handlerMappings;

	@Nullable
	private List<HandlerAdapter> handlerAdapters;

	@Nullable
	private List<HandlerResultHandler> resultHandlers;

	//......

	@Override
	public void setApplicationContext(ApplicationContext applicationContext) {
		initStrategies(applicationContext);
	}


	protected void initStrategies(ApplicationContext context) {
		Map<String, HandlerMapping> mappingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(
				context, HandlerMapping.class, true, false);

		ArrayList<HandlerMapping> mappings = new ArrayList<>(mappingBeans.values());
		AnnotationAwareOrderComparator.sort(mappings);
		this.handlerMappings = Collections.unmodifiableList(mappings);

		Map<String, HandlerAdapter> adapterBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(
				context, HandlerAdapter.class, true, false);

		this.handlerAdapters = new ArrayList<>(adapterBeans.values());
		AnnotationAwareOrderComparator.sort(this.handlerAdapters);

		Map<String, HandlerResultHandler> beans = BeanFactoryUtils.beansOfTypeIncludingAncestors(
				context, HandlerResultHandler.class, true, false);

		this.resultHandlers = new ArrayList<>(beans.values());
		AnnotationAwareOrderComparator.sort(this.resultHandlers);
	}


	@Override
	public Mono<Void> handle(ServerWebExchange exchange) {
		if (logger.isDebugEnabled()) {
			ServerHttpRequest request = exchange.getRequest();
			logger.debug("Processing " + request.getMethodValue() + " request for [" + request.getURI() + "]");
		}
		if (this.handlerMappings == null) {
			return Mono.error(HANDLER_NOT_FOUND_EXCEPTION);
		}
		return Flux.fromIterable(this.handlerMappings)
				.concatMap(mapping -> mapping.getHandler(exchange))
				.next()
				.switchIfEmpty(Mono.error(HANDLER_NOT_FOUND_EXCEPTION))
				.flatMap(handler -> invokeHandler(exchange, handler))
				.flatMap(result -> handleResult(exchange, result));
	}
	//......
}
  • 这里setApplicationContext的时候调用了initStrategies方法
  • 使用BeanFactoryUtils.beansOfTypeIncludingAncestors获取了容器中注册的HandlerMapping
  • RoutePredicateHandlerMapping注册到了容器中,这里会被获取到
  • handlerMapping用于根据exchange来获取handler
  • 这了使用的是concatMap,如果返回的是Mono.empty()则不会被concat,然后next取第一个,即按handlerMappings排序之后的第一个来

handlerMappings

这里按优先级从高到底有如下几个:

  • WebFluxEndpointHandlerMapping(order=-100)
  • ControllerEndpointHandlerMapping(order=-100)
  • RouterFunctionMapping(order=-1)
  • RequestMappingHandlerMapping(order=0)
  • RoutePredicateHandlerMapping(order=1)
  • SimpleUrlHandlerMapping(Ordered.LOWEST_PRECEDENCE)

小结

spring cloud gateway的GlobalFilter在FilteringWebHandler被适配为GatewayFilter,然后与route级别的gatewayFilters进行合并,作用在当前route上面。RoutePredicateHandlerMapping会被DispatcherHandler识别,按order优先级排序,依次根据mapping来获取该exchange的handler,找到不是Mono.empty()的第一个,然后进行invokeHandler以及handleResult。

因此可以理解为GlobalFilter就是全局的GatewayFilter,作用在所有route上面。而GatewayFilter是route级别的。

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