聊聊spring cloud gateway的RouteLocator

序

本文主要研究一下spring cloud gateway的RouteLocator

RouteLocator

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/route/RouteLocator.java

public interface RouteLocator {

	Flux<Route> getRoutes();
}

其有三个实现类：

• RouteDefinitionRouteLocator
• CompositeRouteLocator
• CachingRouteLocator

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 RouteLocatorBuilder routeLocatorBuilder(ConfigurableApplicationContext context) {
		return new RouteLocatorBuilder(context);
	}

	@Bean
	public RouteLocator routeDefinitionRouteLocator(GatewayProperties properties,
												   List<GatewayFilterFactory> GatewayFilters,
												   List<RoutePredicateFactory> predicates,
												   RouteDefinitionLocator routeDefinitionLocator) {
		return new RouteDefinitionRouteLocator(routeDefinitionLocator, predicates, GatewayFilters, properties);
	}

	@Bean
	@Primary
	//TODO: property to disable composite?
	public RouteLocator cachedCompositeRouteLocator(List<RouteLocator> routeLocators) {
		return new CachingRouteLocator(new CompositeRouteLocator(Flux.fromIterable(routeLocators)));
	}

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

	@Configuration
	@ConditionalOnClass(Health.class)
	protected static class GatewayActuatorConfiguration {

		@Bean
		@ConditionalOnEnabledEndpoint
		public GatewayControllerEndpoint gatewayControllerEndpoint(RouteDefinitionLocator routeDefinitionLocator, List<GlobalFilter> globalFilters,
																List<GatewayFilterFactory> GatewayFilters, RouteDefinitionWriter routeDefinitionWriter,
																RouteLocator routeLocator) {
			return new GatewayControllerEndpoint(routeDefinitionLocator, globalFilters, GatewayFilters, routeDefinitionWriter, routeLocator);
		}
	}
	//......
}

可以看到默认创建了RouteDefinitionRouteLocator，然后又基于它创建了CompositeRouteLocator，最后由CachingRouteLocator再包装一层

RouteDefinitionRouteLocator

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/route/RouteDefinitionRouteLocator.java

/**
 * {@link RouteLocator} that loads routes from a {@link RouteDefinitionLocator}
 * @author Spencer Gibb
 */
public class RouteDefinitionRouteLocator implements RouteLocator, BeanFactoryAware, ApplicationEventPublisherAware {
	protected final Log logger = LogFactory.getLog(getClass());

	private final RouteDefinitionLocator routeDefinitionLocator;
	private final Map<String, RoutePredicateFactory> predicates = new LinkedHashMap<>();
	private final Map<String, GatewayFilterFactory> gatewayFilterFactories = new HashMap<>();
	private final GatewayProperties gatewayProperties;
	private final SpelExpressionParser parser = new SpelExpressionParser();
	private BeanFactory beanFactory;
	private ApplicationEventPublisher publisher;

	public RouteDefinitionRouteLocator(RouteDefinitionLocator routeDefinitionLocator,
									   List<RoutePredicateFactory> predicates,
									   List<GatewayFilterFactory> gatewayFilterFactories,
									   GatewayProperties gatewayProperties) {
		this.routeDefinitionLocator = routeDefinitionLocator;
		initFactories(predicates);
		gatewayFilterFactories.forEach(factory -> this.gatewayFilterFactories.put(factory.name(), factory));
		this.gatewayProperties = gatewayProperties;
	}

	@Autowired
	private Validator validator;

	@Override
	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
		this.beanFactory = beanFactory;
	}

	@Override
	public void setApplicationEventPublisher(ApplicationEventPublisher publisher) {
		this.publisher = publisher;
	}

	private void initFactories(List<RoutePredicateFactory> predicates) {
		predicates.forEach(factory -> {
			String key = factory.name();
			if (this.predicates.containsKey(key)) {
				this.logger.warn("A RoutePredicateFactory named "+ key
						+ " already exists, class: " + this.predicates.get(key)
						+ ". It will be overwritten.");
			}
			this.predicates.put(key, factory);
			if (logger.isInfoEnabled()) {
				logger.info("Loaded RoutePredicateFactory [" + key + "]");
			}
		});
	}

	@Override
	public Flux<Route> getRoutes() {
		return this.routeDefinitionLocator.getRouteDefinitions()
				.map(this::convertToRoute)
				//TODO: error handling
				.map(route -> {
					if (logger.isDebugEnabled()) {
						logger.debug("RouteDefinition matched: " + route.getId());
					}
					return route;
				});


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

	//......
}

• 这个类名有点绕，如同注释里头说的，它是一个routeLocator，从routeDefinitionLocator获取Route信息
• 这里注入的routeDefinitionLocator是CompositeRouteDefinitionLocator，它组合了InMemoryRouteDefinitionRepository、PropertiesRouteDefinitionLocator、DiscoveryClientRouteDefinitionLocator三个RouteDefinitionLocator。
• PropertiesRouteDefinitionLocator是直接使用GatewayProperties的getRoutes()获取，其是通过spring.cloud.gateway.routes配置得来。

convertToRoute

	private Route convertToRoute(RouteDefinition routeDefinition) {
		Predicate<ServerWebExchange> predicate = combinePredicates(routeDefinition);
		List<GatewayFilter> gatewayFilters = getFilters(routeDefinition);

		return Route.builder(routeDefinition)
				.predicate(predicate)
				.replaceFilters(gatewayFilters)
				.build();
	}

RouteDefinitionRouteLocator的getRoutes方法，从routeDefinitionLocator.getRouteDefinitions()，然后使用convertToRoute方法进行转换，该方法主要用到了combinePredicates、getFilters两个方法

combinePredicates

	private Predicate<ServerWebExchange> combinePredicates(RouteDefinition routeDefinition) {
		List<PredicateDefinition> predicates = routeDefinition.getPredicates();
		Predicate<ServerWebExchange> predicate = lookup(routeDefinition, predicates.get(0));

		for (PredicateDefinition andPredicate : predicates.subList(1, predicates.size())) {
			Predicate<ServerWebExchange> found = lookup(routeDefinition, andPredicate);
			predicate = predicate.and(found);
		}

		return predicate;
	}

	private Predicate<ServerWebExchange> lookup(RouteDefinition route, PredicateDefinition predicate) {
		RoutePredicateFactory<Object> factory = this.predicates.get(predicate.getName());
		if (factory == null) {
            throw new IllegalArgumentException("Unable to find RoutePredicateFactory with name " + predicate.getName());
		}
		Map<String, String> args = predicate.getArgs();
		if (logger.isDebugEnabled()) {
			logger.debug("RouteDefinition " + route.getId() + " applying "
					+ args + " to " + predicate.getName());
		}

        Map<String, Object> properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);
        Object config = factory.newConfig();
        ConfigurationUtils.bind(config, properties,
                factory.shortcutFieldPrefix(), predicate.getName(), validator);
        if (this.publisher != null) {
            this.publisher.publishEvent(new PredicateArgsEvent(this, route.getId(), properties));
        }
        return factory.apply(config);
	}

这里利用工厂方法，根据config去apply出来Predicate<ServerWebExchange> 而combinePredicates主要是对找出来的predicate进行and操作

getFilters

	private List<GatewayFilter> getFilters(RouteDefinition routeDefinition) {
		List<GatewayFilter> filters = new ArrayList<>();

		//TODO: support option to apply defaults after route specific filters?
		if (!this.gatewayProperties.getDefaultFilters().isEmpty()) {
			filters.addAll(loadGatewayFilters("defaultFilters",
					this.gatewayProperties.getDefaultFilters()));
		}

		if (!routeDefinition.getFilters().isEmpty()) {
			filters.addAll(loadGatewayFilters(routeDefinition.getId(), routeDefinition.getFilters()));
		}

		AnnotationAwareOrderComparator.sort(filters);
		return filters;
	}

	private List<GatewayFilter> loadGatewayFilters(String id, List<FilterDefinition> filterDefinitions) {
		List<GatewayFilter> filters = filterDefinitions.stream()
				.map(definition -> {
					GatewayFilterFactory factory = this.gatewayFilterFactories.get(definition.getName());
					if (factory == null) {
                        throw new IllegalArgumentException("Unable to find GatewayFilterFactory with name " + definition.getName());
					}
					Map<String, String> args = definition.getArgs();
					if (logger.isDebugEnabled()) {
						logger.debug("RouteDefinition " + id + " applying filter " + args + " to " + definition.getName());
					}

                    Map<String, Object> properties = factory.shortcutType().normalize(args, factory, this.parser, this.beanFactory);

                    Object configuration = factory.newConfig();

                    ConfigurationUtils.bind(configuration, properties,
                            factory.shortcutFieldPrefix(), definition.getName(), validator);

                    GatewayFilter gatewayFilter = factory.apply(configuration);
                    if (this.publisher != null) {
                        this.publisher.publishEvent(new FilterArgsEvent(this, id, properties));
                    }
                    return gatewayFilter;
				})
				.collect(Collectors.toList());

		ArrayList<GatewayFilter> ordered = new ArrayList<>(filters.size());
		for (int i = 0; i < filters.size(); i++) {
			GatewayFilter gatewayFilter = filters.get(i);
			if (gatewayFilter instanceof Ordered) {
				ordered.add(gatewayFilter);
			}
			else {
				ordered.add(new OrderedGatewayFilter(gatewayFilter, i + 1));
			}
		}

		return ordered;
	}

getFilters主要是利用loadGatewayFilters获取filter，返回使用AnnotationAwareOrderComparator进行排序 loadGatewayFilters也是利用工厂方法，使用GatewayFilterFactory根据config去apply出来具体的GatewayFilter实例

小结

RouteLocator接口用于获取路由信息，其有三个实现类

• RouteDefinitionRouteLocator
• CompositeRouteLocator
• CachingRouteLocator

最终使用的是CachingRouteLocator，它包装了CompositeRouteLocator，而CompositeRouteLocator则组合了RouteDefinitionRouteLocator。

RouteDefinitionRouteLocator与RouteDefinitionLocator比较容易混淆，前者是一个RouteLocator，后者是一个RouteDefinitionLocator，前者的RouteDefinitionRouteLocator主要从后者获取路由定义信息。

doc

• 114. Configuration
• 114.1 Fluent Java Routes API