Spring Cloud Gateway(三):网关处理器 柔情只为你懂 2022-04-17 02:00 326阅读 0赞 # 1、Spring Cloud Gateway 源码解析概述 # API网关作为后端服务的统一入口,可提供请求路由、协议转换、安全认证、服务鉴权、流量控制、日志监控等服务。那么当请求到达网关时,网关都做了哪些处理以及怎么处理的呢?我们带着这些问题,顺着网关的处理流程,一步步进行源码阅读,一探究竟。 # 2、Spring Cloud Gateway 网关处理流程概述 # ![image][] 1、请求发送到网关, DispatcherHandler 是HTTP请求的中央分发器,将请求匹配到响应的HandlerMapping; 2、请求与处理器之间有一个映射关系,网关将会对请求进行路由,handler会匹配到RoutePredicateHandlerMapping,以匹配到对应的Route 3、接着请求到达网关的web处理器,该WebHandler 代理了一系列网关过滤器和全局过滤器的实例,此时会对请求头或响应头进行处理 4、最后转发到具体的代理服务 # 3、Spring Cloud Gateway 初始化 # 当启动网关服务时,引入的Spring Cloud Gateway 的starter将会自动加载一些配置: # Auto Configure org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ # WebFlux 依赖检查配置类 org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration,\ # 网关核心自动配置类,配置路由规则、过滤器等 org.springframework.cloud.gateway.config.GatewayAutoConfiguration,\ # 客户端负载均衡自动配置类 org.springframework.cloud.gateway.config.GatewayLoadBalancerClientAutoConfiguration,\ # 网关指标自动配置类 org.springframework.cloud.gateway.config.GatewayMetricsAutoConfiguration,\ # redis 自动配置类 org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration,\ # 服务发现客户端自动配置类 org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration 下面不会一一列出以上的配置,这里主要看一下设计网关属性的配置。GatewayProperties是网关配置中的核心配置属性类: @ConfigurationProperties("spring.cloud.gateway") @Validated public class GatewayProperties { //路由列表 @NotNull @Valid private List<RouteDefinition> routes = new ArrayList(); //默认过滤器 private List<FilterDefinition> defaultFilters = new ArrayList(); //流媒体类型 private List<MediaType> streamingMediaTypes; public GatewayProperties() { this.streamingMediaTypes = Arrays.asList(MediaType.TEXT_EVENT_STREAM, MediaType.APPLICATION_STREAM_JSON); } public List<RouteDefinition> getRoutes() { return this.routes; } public void setRoutes(List<RouteDefinition> routes) { this.routes = routes; } public List<FilterDefinition> getDefaultFilters() { return this.defaultFilters; } public void setDefaultFilters(List<FilterDefinition> defaultFilters) { this.defaultFilters = defaultFilters; } public List<MediaType> getStreamingMediaTypes() { return this.streamingMediaTypes; } public void setStreamingMediaTypes(List<MediaType> streamingMediaTypes) { this.streamingMediaTypes = streamingMediaTypes; } public String toString() { return "GatewayProperties{routes=" + this.routes + ", defaultFilters=" + this.defaultFilters + ", streamingMediaTypes=" + this.streamingMediaTypes + '}'; } } GatewayProperties 有三个属性,分别是路由列表(对应路由定义对象RouteDefinition)、默认过滤器列表(对应过滤器对象FilterDefinition)、流媒体类型列表(对应流媒体对象MediaType) # 4、网关处理器 # 当请求到达网关时,会有各种web处理器对请求进行匹配和处理,下面我们将会对主要的几个web处理器进行讲解 ![image][image 1] graph LR DispatcherHandler -->RoutePredicateHandlerMapping RoutePredicateHandlerMapping-->FilteringWebHandler FilteringWebHandler-->DefaultGatewayFilterChain ## 4.1、请求分发器 DispatcherHandler ## Spring Cloud Gateway 引入了Spring WebFlux, DispatcherHandler 是 请求分发处理器,是网关请求的入口。之前的项目中引入的是 Spring MVC,它的分发 处理器是 DispatcherServlet。下面看一下网关收到请求后是如何处理的: public class DispatcherHandler implements WebHandler, ApplicationContextAware { private static final Exception HANDLER_NOT_FOUND_EXCEPTION; private static final Log logger; @Nullable private List<HandlerMapping> handlerMappings; @Nullable private List<HandlerAdapter> handlerAdapters; @Nullable private List<HandlerResultHandler> resultHandlers; public DispatcherHandler() { } public DispatcherHandler(ApplicationContext applicationContext) { this.initStrategies(applicationContext); } @Nullable public final List<HandlerMapping> getHandlerMappings() { return this.handlerMappings; } public void setApplicationContext(ApplicationContext applicationContext) { this.initStrategies(applicationContext); } //根据请求匹配对应的出列器 public Mono<Void> handle(ServerWebExchange exchange) { if (logger.isDebugEnabled()) { ServerHttpRequest request = exchange.getRequest(); logger.debug("Processing " + request.getMethodValue() + " request for [" + request.getURI() + "]"); } return this.handlerMappings == null ? Mono.error(HANDLER_NOT_FOUND_EXCEPTION) : Flux.fromIterable(this.handlerMappings).concatMap((mapping) -> { return mapping.getHandler(exchange); }).next().switchIfEmpty(Mono.error(HANDLER_NOT_FOUND_EXCEPTION)).flatMap((handler) -> { return this.invokeHandler(exchange, handler); }).flatMap((result) -> { return this.handleResult(exchange, result); }); } private Mono<HandlerResult> invokeHandler(ServerWebExchange exchange, Object handler) { if (this.handlerAdapters != null) { for (HandlerAdapter handlerAdapter : this.handlerAdapters) { if (handlerAdapter.supports(handler)) { return handlerAdapter.handle(exchange, handler); } } } return Mono.error(new IllegalStateException("No HandlerAdapter: " + handler)); } private Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) { return getResultHandler(result).handleResult(exchange, result) .onErrorResume(ex -> result.applyExceptionHandler(ex).flatMap(exceptionResult -> getResultHandler(exceptionResult).handleResult(exchange, exceptionResult))); } private HandlerResultHandler getResultHandler(HandlerResult handlerResult) { if (this.resultHandlers != null) { for (HandlerResultHandler resultHandler : this.resultHandlers) { if (resultHandler.supports(handlerResult)) { return resultHandler; } } } throw new IllegalStateException("No HandlerResultHandler for " + handlerResult.getReturnValue()); } } DispatcherHandler 实现了 WebHandler 接口,WebHandler 接口是用来处理 Web请求的。在DispatcherHandler 的构造函数中会初始化 HandlerMapping,核心 处理 的方法是 handle( ServerWebExchange exchange), 而 HandlerMapping 是一个定义 了请求与处理器对象映射的接口且有多个实现类,如 ControllerEndpointHandlerMapping 和 RouterFunctionMapping。 invokeHandler 方法调用相应的 WebHandler,获取该WebHandler对应的适配器。 ## 4.2、路由断言处理器 RoutePredicateHandlerMapping ## RoutePredicateHandlerMapping 用于匹配具体的Route,并返回处理 Route 的 FilteringWebHandler public class RoutePredicateHandlerMapping extends AbstractHandlerMapping { private final FilteringWebHandler webHandler; private final RouteLocator routeLocator; public RoutePredicateHandlerMapping(FilteringWebHandler webHandler, RouteLocator routeLocator, GlobalCorsProperties globalCorsProperties) { this.webHandler = webHandler; this.routeLocator = routeLocator; this.setOrder(1); this.setCorsConfigurations(globalCorsProperties.getCorsConfigurations()); } ................................ } RoutePredicateHandlerMapping 的构造函数接受两个参数, FilteringWebHandler 网关过滤器 和 RouteLocator 路由定位器, setOrder( 1) 用于设置该对象初始化的优先级。 Spring Cloud Gateway 的 GatewayWebfluxEndpoint 提供的 HTTP API 不需要经过 网关转发,它通过 RequestMappingHandlerMapping 进行请求匹配处理,因此需要将 RoutePredicateHandlerMapping 的优先级设置为 低于RequestMappingHandlerMapping。 protected Mono<?> getHandlerInternal(ServerWebExchange exchange) { //设置网关处理器为 RoutePredicateHandlerMapping exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_HANDLER_MAPPER_ATTR, this.getClass().getSimpleName()); return this.lookupRoute(exchange).flatMap((r) -> { exchange.getAttributes().remove(ServerWebExchangeUtils.GATEWAY_PREDICATE_ROUTE_ATTR); if (this.logger.isDebugEnabled()) { this.logger.debug("Mapping [" + this.getExchangeDesc(exchange) + "] to " + r); } exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR, r); return Mono.just(this.webHandler); }).switchIfEmpty(Mono.empty().then(Mono.fromRunnable(() -> { exchange.getAttributes().remove(ServerWebExchangeUtils.GATEWAY_PREDICATE_ROUTE_ATTR); if (this.logger.isTraceEnabled()) { this.logger.trace("No RouteDefinition found for [" + this.getExchangeDesc(exchange) + "]"); } }))); } //路由顺序匹配 protected Mono<Route> lookupRoute(ServerWebExchange exchange) { return this.routeLocator.getRoutes().concatMap((route) -> { return Mono.just(route).filterWhen((r) -> { exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_PREDICATE_ROUTE_ATTR, r.getId()); return (Publisher)r.getPredicate().apply(exchange); }).doOnError((e) -> { this.logger.error("Error applying predicate for route: " + route.getId(), e); }).onErrorResume((e) -> { return Mono.empty(); }); }).next().map((route) -> { if (this.logger.isDebugEnabled()) { this.logger.debug("Route matched: " + route.getId()); } //校验路由有效性 this.validateRoute(route, exchange); return route; }); } 以上为获取 handler 的方法,匹配请求的Route,并返回处理 Route的过滤器 FilteringWebHandler。 首先设置GATEWAY\_ HANDLER\_ MAPPER\_ ATTR 为 RoutePredicateHandlerMapping 的类名 然后顺序匹配对应的 Route,RouteLocator 接口获取网关中定义的路由,并根据请求信息与路由定义的断言按照优先级匹配。 最后找到匹配的Route,并返回响应的处理器。 ## 4.3、过滤器处理器 FilteringWebHandler ## FilteringWebHandler 通过创建所请求 Route 对应的 GatewayFilterChain, 在网关进行过滤处理 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 (List)filters.stream().map((filter) -> { //适配 GatewayFilter FilteringWebHandler.GatewayFilterAdapter gatewayFilter = new FilteringWebHandler.GatewayFilterAdapter(filter); //是否实现了 Ordered,如果实现了,则返回OrderedGatewayFilter if (filter instanceof Ordered) { int order = ((Ordered)filter).getOrder(); return new OrderedGatewayFilter(gatewayFilter, order); } else { return gatewayFilter; } }).collect(Collectors.toList()); } public Mono<Void> handle(ServerWebExchange exchange) { Route route = (Route)exchange.getRequiredAttribute(ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR); List<GatewayFilter> gatewayFilters = route.getFilters(); List<GatewayFilter> combined = new ArrayList(this.globalFilters); //加入全局过滤器 combined.addAll(gatewayFilters); //过滤器排序 AnnotationAwareOrderComparator.sort(combined); logger.debug("Sorted gatewayFilterFactories: " + combined); //按照优先级对请求进行过滤 return (new FilteringWebHandler.DefaultGatewayFilterChain(combined)).filter(exchange); } } 全局变量 globalFilters 是Spring Cloud Gateway 定义的全局过滤器,构造函数通过传入全局过滤器,对过滤器进行适配。因为过滤器有优先级,loadFilters 该方法主要是判断过滤器是否实现了 Ordered 接口,如果实现了则返回OrderedGatewayFilter,否则返回适配的过滤器。最后将适配的过滤器加入全局过滤器,并对过滤器进行排序,根据优先级对请求进行处理。 ## 4.4、生成过滤器链 ## FilteringWebHandler 内部静态类 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(FilteringWebHandler.DefaultGatewayFilterChain parent, int index) { this.filters = parent.getFilters(); this.index = index; } public List<GatewayFilter> getFilters() { return this.filters; } public Mono<Void> filter(ServerWebExchange exchange) { return Mono.defer(() -> { if (this.index < this.filters.size()) { GatewayFilter filter = (GatewayFilter)this.filters.get(this.index); FilteringWebHandler.DefaultGatewayFilterChain chain = new FilteringWebHandler.DefaultGatewayFilterChain(this, this.index + 1); return filter.filter(exchange, chain); } else { return Mono.empty(); } }); } } FilteringWebHandler 的 handle 方法,首先获取请求对应的路由过滤器和全局过滤器,并将两者合并。 然后对过滤器进行排序。 最后按照优先级生成过滤器链,对请求进行过滤处理。 过滤器链的生成是通过内部静态类 DefaultGatewayFilterChain 实现的,该类实现了GatewayFilterChain 接口,最后对请求按照过滤器优先级进行过滤。 [image]: /images/20220417/1b9aa61c0d924a8d960c0663a1b107a4.png [image 1]: /images/20220417/8acbd6404c634210b23aa6b57eb4351b.png
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