spring cloud gateway源码解析

1.gateway 和zuul对比

1.zuul是基于servlet 2.5，兼容servlet3.0，使用的是阻塞API，不支持长连接如websocket

2.Gateway基于spring5，Reactor和Spring boot2使用了非阻塞API，支持websocket，和spring完美集成，对开发者友好。

3.zuul2支持非阻塞API，但没有和spring cloud集成，且已经停止维护，不在考虑之列。

2.架构图

3.自动配置

看spring-cloud-gateway-core包下的 spring.factories

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayLoadBalancerClientAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayNoLoadBalancerClientAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayMetricsAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration,\
org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration
org.springframework.boot.env.EnvironmentPostProcessor=\
org.springframework.cloud.gateway.config.GatewayEnvironmentPostProcessor

 3.1 GatewayClassPathWarningAutoConfiguration检查前端控制器

package org.springframework.cloud.gateway.config;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.boot.autoconfigure.AutoConfigureBefore;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
import org.springframework.context.annotation.Configuration;

@Configuration
@AutoConfigureBefore(GatewayAutoConfiguration.class)
public class GatewayClassPathWarningAutoConfiguration {

	private static final Log log = LogFactory
			.getLog(GatewayClassPathWarningAutoConfiguration.class);

	private static final String BORDER = "\n\n**********************************************************\n\n";

	@Configuration
	@ConditionalOnClass(name = "org.springframework.web.servlet.DispatcherServlet")
	protected static class SpringMvcFoundOnClasspathConfiguration {

		public SpringMvcFoundOnClasspathConfiguration() {
			log.warn(BORDER
					+ "Spring MVC found on classpath, which is incompatible with Spring Cloud Gateway at this time. "
					+ "Please remove spring-boot-starter-web dependency." + BORDER);
		}

	}

	@Configuration
	@ConditionalOnMissingClass("org.springframework.web.reactive.DispatcherHandler")
	protected static class WebfluxMissingFromClasspathConfiguration {

		public WebfluxMissingFromClasspathConfiguration() {
			log.warn(BORDER + "Spring Webflux is missing from the classpath, "
					+ "which is required for Spring Cloud Gateway at this time. "
					+ "Please add spring-boot-starter-webflux dependency." + BORDER);
		}

	}

}

解释：

1.若存在springmvc的前端控制器org.springframework.web.servlet.DispatcherServlet，则报警,原因是使用非阻塞的API。

2.若不存在spring webflux的前端控制器org.springframework.web.reactive.DispatcherHandler，则报警,原因是需要使用非阻塞的API。

3.2 网关自动配置GatewayAutoConfiguration

 

3.2.1 RoutePredicateHandlerMapping

	@Bean
	public RoutePredicateHandlerMapping routePredicateHandlerMapping(
			FilteringWebHandler webHandler, RouteLocator routeLocator,
			GlobalCorsProperties globalCorsProperties, Environment environment) {
		return new RoutePredicateHandlerMapping(webHandler, routeLocator,
				globalCorsProperties, environment);
	}

RoutePredicateHandlerMapping继承自AbstractHandlerMapping，在此步进行路径查找

	@Override
	protected Mono<?> getHandlerInternal(ServerWebExchange exchange) {
		// don't handle requests on management port if set and different than server port
		if (this.managementPortType == DIFFERENT && this.managementPort != null
				&& exchange.getRequest().getURI().getPort() == this.managementPort) {
			return Mono.empty();
		}
		exchange.getAttributes().put(GATEWAY_HANDLER_MAPPER_ATTR, 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) + "]");
					}
				})));
	}

	protected Mono<Route> lookupRoute(ServerWebExchange exchange) {
		return this.routeLocator.getRoutes()
				// individually filter routes so that filterWhen error delaying is not a
				// problem
				.concatMap(route -> Mono.just(route).filterWhen(r -> {
					// add the current route we are testing
					exchange.getAttributes().put(GATEWAY_PREDICATE_ROUTE_ATTR, r.getId());
					return r.getPredicate().apply(exchange);
				})
						// instead of immediately stopping main flux due to error, log and
						// swallow it
						.doOnError(e -> logger.error(
								"Error applying predicate for route: " + route.getId(),
								e))
						.onErrorResume(e -> Mono.empty()))
				// .defaultIfEmpty() put a static Route not found
				// or .switchIfEmpty()
				// .switchIfEmpty(Mono.<Route>empty().log("noroute"))
				.next()
				// TODO: error handling
				.map(route -> {
					if (logger.isDebugEnabled()) {
						logger.debug("Route matched: " + route.getId());
					}
					validateRoute(route, exchange);
					return route;
				});

		/*
		 * TODO: trace logging if (logger.isTraceEnabled()) {
		 * logger.trace("RouteDefinition did not match: " + routeDefinition.getId()); }
		 */
	}

1.通过RouteLocator返回Route

 关于Route的定义

可以看出url和gatewayFilter进行了绑定

 2.将Route放入ServerWebExchange的属性中。

3.2.2 FilteringWebHandler

	@Bean
	public FilteringWebHandler filteringWebHandler(List<GlobalFilter> globalFilters) {
		return new FilteringWebHandler(globalFilters);
	}