Spring Cloud Gateway 源码剖析之Route数据模型五、总结

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我是靠谱客的博主英俊枕头，最近开发中收集的这篇文章主要介绍Spring Cloud Gateway 源码剖析之Route数据模型五、总结，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

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一、前言

我们上一篇讲了：Spring Cloud Gateway 源码剖析之配置初始化，通过自动加载初始化六个配置实例，Spring Cloud Gateway 就完成自身的加载和初始化工作。我们知道 Gateway 的核心是路由加过滤，既然网关相关初始化工作做好了，那得开始路由相关的工作了。

接下来我们就来分析下平时在 properties 或者 yml 中配置的有关 Gateway 的配置是如何构建成 Route 的。

二、Route 构建方式

一般构建分为两种：外部化配置和编程方式

1、外部化配置

spring:
  cloud:
    gateway:
      routes: 
      - id: after_route // ①
        uri: https://example.org // ②
        predicates: 
        - Cookie=mycookie,mycookievalue // ③
        filters: 
        - AddRequestHeader=X-Request-Foo, Bar // ④

① 配置了一个 Route id 为 after_route
② 客户端请求转发的目的地：https://example.org
③ 在 request 中，当存在名字 mycookie 的 cookie 的值匹配 mycookievalue 则算成功
④ 定义了一个 Filter，匹配成功后，会在请求头上添加 X-Request-Foo:Bar

2、编程方式

用上面的例子，转换成编程方式

@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
   builder.routes()
		.route(r -> r.cookie("mycookie", "mycookievalue")
			.filters(f -> f.addRequestHeader("X-Request-Foo", "Bar"))
			.uri("https://example.org")
		)
		.build();
}

简单介绍了构建 Route 的两种方式，下面分析 Route 是如何把外部化配置与编码配置之间进行转换。

三、Route 构建原理

1、外部化配置

外部化配置是通过 GatewayProperties 进行构建的

/**
 * 网关配置信息加载
 * 从appliccation.yml中解析前缀为spring.cloud.gateway的配置
 */
@ConfigurationProperties("spring.cloud.gateway")
@Validated
public class GatewayProperties {
    private final Log logger = LogFactory.getLog(this.getClass());
    
    /**
     * 路由定义列表
     * 加载配置key=spring.cloud.gateway.routes 列表
     * List of Routes
     */
    @NotNull
    @Valid
    private List<RouteDefinition> routes = new ArrayList();
    
    /**
     * 默认的过滤器定义列表
     * 加载配置 key = spring.cloud.gateway.default-filters 列表
     * List of filter definitions that are applied to every route.
     */
    private List<FilterDefinition> defaultFilters = new ArrayList();
    
    /**
     * 网媒体类型列表
     * 加载配置 key = spring.cloud.gateway.streamingMediaTypes 列表
     * 默认包含{text/event-stream,application/stream+json}
     */
    private List<MediaType> streamingMediaTypes;

	public GatewayProperties() {
        this.streamingMediaTypes = Arrays.asList(MediaType.TEXT_EVENT_STREAM, MediaType.APPLICATION_STREAM_JSON);
    }

	...
}

1.1 RouteDefinition

用来对 Route 进行定义。也就是，通过 GatewayProperties 会与外部化配置进行绑定，把外部化配置比如 properties 或者 yml 绑定到 GatewayProperties 中。

/**
 * 路由定义实体信息，包含路由的定义信息
 */
@Validated
public class RouteDefinition {
	/**
     * 路由ID 编号，唯一
     */
    @NotEmpty
    private String id = UUID.randomUUID().toString();

	/**
     * 谓语定义数组
     * predicates 属性，谓语定义数组
     * 请求通过   判断是否匹配。在 Route 里，PredicateDefinition 转换成 Predicate
     */
    @NotEmpty
    @Valid
    private List<PredicateDefinition> predicates = new ArrayList();
    
    /**
     * 过滤器定义数组
     * filters 属性，过滤器定义数组。
     * 在 Route 里，FilterDefinition 转换成 GatewayFilter
     */
    @Valid
    private List<FilterDefinition> filters = new ArrayList();

	/**
     * 路由指向的URI
     */
    @NotNull
    private URI uri;

	/**
     * 顺序
     */
    private int order = 0;

	...
}

1.2 PredicateDefinition

/**
 * 谓语定义,在 Route 里，PredicateDefinition 将转换成 Predicate
 */
@Validated
public class PredicateDefinition {
	/**
     * 谓语定义名字
     * 通过 name 对应到 org.springframework.cloud.gateway.handler.predicate.RoutePredicateFactory 的实现类。
     * 例如: name=Query 对应到 QueryRoutePredicateFactory
     */
    @NotNull
    private String name;

	/**
     * 参数数组
     * 例如，name=Host / args={"_genkey_0" : "iocoder.cn"} ，匹配请求的 hostname 为 iocoder.cn
     */
    private Map<String, String> args = new LinkedHashMap();

	...
}

1.3 FilterDefinition

/**
 * 过滤器定义，在 Route 里，FilterDefinition将转换成 GatewayFilter
 */
@Validated
public class FilterDefinition {
	/**
     * 过滤器定义名字
     * 通过 name 对应到 org.springframework.cloud.gateway.filter.factory.GatewayFilterFactory 的实现类。
     * 例如，name=AddRequestParameter 对应到 AddRequestParameterGatewayFilterFactory
     */
    @NotNull
    private String name;

	/**
     * 参数数组
     * 例如 name=AddRequestParameter / args={"_genkey_0": "foo", "_genkey_1": "bar"} ，添加请求参数 foo 为 bar
     */
    private Map<String, String> args = new LinkedHashMap();

	...
}

1.4 RouteDefinitionLocator

在上一篇文章 Spring Cloud Gateway 源码剖析之配置初始化中的 GatewayAutoConfiguration 核心配置类中，有提到此类。

@Bean
@Primary
public RouteDefinitionLocator routeDefinitionLocator(List<RouteDefinitionLocator> routeDefinitionLocators) {
    return new CompositeRouteDefinitionLocator(Flux.fromIterable(routeDefinitionLocators));
}

Gateway 提供多种方式来获取外部的配置，而 RouteDefinitionLocator 就是父接口，下面有多种实现。

在这里插入图片描述

1.4.1 PropertiesRouteDefinitionLocator

从配置文件(YML、Properties 等) 读取路由配置。代码如下：

public class PropertiesRouteDefinitionLocator implements RouteDefinitionLocator {
    private final GatewayProperties properties;

    public PropertiesRouteDefinitionLocator(GatewayProperties properties) {
        this.properties = properties;
    }

    public Flux<RouteDefinition> getRouteDefinitions() {
    	// 从 GatewayProperties 获取路由配置数组。
        return Flux.fromIterable(this.properties.getRoutes());
    }
}

1.4.2 InMemoryRouteDefinitionRepository

从存储器(内存、Redis、MySQL 等)读取、保存、删除路由配置。InMemoryRouteDefinitionRepository 是基于内存的。

public class InMemoryRouteDefinitionRepository implements RouteDefinitionRepository {
	/**
   	 * 路由配置映射 通过此来保存route
     * key ：路由编号 {@link RouteDefinition#id}
     */
    private final Map<String, RouteDefinition> routes = Collections.synchronizedMap(new LinkedHashMap());

    public InMemoryRouteDefinitionRepository() {
    }

    public Mono<Void> save(Mono<RouteDefinition> route) {
        return route.flatMap((r) -> {
            this.routes.put(r.getId(), r);
            return Mono.empty();
        });
    }

    public Mono<Void> delete(Mono<String> routeId) {
        return routeId.flatMap((id) -> {
            if (this.routes.containsKey(id)) {
                this.routes.remove(id);
                return Mono.empty();
            } else {
                return Mono.defer(() -> {
                    return Mono.error(new NotFoundException("RouteDefinition not found: " + routeId));
                });
            }
        });
    }

    public Flux<RouteDefinition> getRouteDefinitions() {
        return Flux.fromIterable(this.routes.values());
    }
}

基于内存，通过 Map<String, RouteDefinition> routes 来保存 Route，缺点是如果重启，那么 route 会丢失。可以实现 RouteDefinitionRepository 接口自定义比如通过 Redis、Mysql 等来保存 Route。

1.4.3 DiscoveryClientRouteDefinitionLocator

获取在注册中心的服务列表，生成对应的 RouteDefinition 数组。

public class DiscoveryClientRouteDefinitionLocator implements RouteDefinitionLocator {
    private static final Log log = LogFactory.getLog(DiscoveryClientRouteDefinitionLocator.class);
    private final DiscoveryClient discoveryClient;
    private final DiscoveryLocatorProperties properties;
    private final String routeIdPrefix;
    private final SimpleEvaluationContext evalCtxt;

    public DiscoveryClientRouteDefinitionLocator(DiscoveryClient discoveryClient, DiscoveryLocatorProperties properties) {
        this.discoveryClient = discoveryClient;
        this.properties = properties;
        if (StringUtils.hasText(properties.getRouteIdPrefix())) {
            this.routeIdPrefix = properties.getRouteIdPrefix();
        } else {
            this.routeIdPrefix = this.discoveryClient.getClass().getSimpleName() + "_";
        }

        this.evalCtxt = SimpleEvaluationContext.forReadOnlyDataBinding().withInstanceMethods().build();
    }

    public Flux<RouteDefinition> getRouteDefinitions() {
        SpelExpressionParser parser = new SpelExpressionParser();
        Expression includeExpr = parser.parseExpression(this.properties.getIncludeExpression());
        Expression urlExpr = parser.parseExpression(this.properties.getUrlExpression());
        Predicate includePredicate;
        if (this.properties.getIncludeExpression() != null && !"true".equalsIgnoreCase(this.properties.getIncludeExpression())) {
            includePredicate = (instance) -> {
                Boolean include = (Boolean)includeExpr.getValue(this.evalCtxt, instance, Boolean.class);
                return include == null ? false : include;
            };
        } else {
            includePredicate = (instance) -> {
                return true;
            };
        }
		// 获取discoveryClient，然后发起请求
        Flux var10000 = Flux.fromIterable(this.discoveryClient.getServices());
        DiscoveryClient var10001 = this.discoveryClient;
        var10001.getClass();
        return var10000.map(var10001::getInstances).filter((instances) -> {
            return !instances.isEmpty();
        }).map((instances) -> {
            return (ServiceInstance)instances.get(0);
        }).filter(includePredicate).map((instance) -> {
            String serviceId = instance.getServiceId();
            RouteDefinition routeDefinition = new RouteDefinition();
            // 设置 ID
            routeDefinition.setId(this.routeIdPrefix + serviceId);
            // 设置 uri
            String uri = (String)urlExpr.getValue(this.evalCtxt, instance, String.class);
            routeDefinition.setUri(URI.create(uri));
            ServiceInstance instanceForEval = new DiscoveryClientRouteDefinitionLocator.DelegatingServiceInstance(instance, this.properties);
            Iterator var8 = this.properties.getPredicates().iterator();

            Iterator var11;
            Entry entry;
            String value;
            
            while(var8.hasNext()) {
                PredicateDefinition originalx = (PredicateDefinition)var8.next();
                // 添加 path 断言
                PredicateDefinition predicate = new PredicateDefinition();
                predicate.setName(originalx.getName());
                var11 = originalx.getArgs().entrySet().iterator();

                while(var11.hasNext()) {
                    entry = (Entry)var11.next();
                    value = this.getValueFromExpr(this.evalCtxt, parser, instanceForEval, entry);
                    predicate.addArg((String)entry.getKey(), value);
                }

                routeDefinition.getPredicates().add(predicate);
            }

            var8 = this.properties.getFilters().iterator();

            while(var8.hasNext()) {
                FilterDefinition original = (FilterDefinition)var8.next();
                // 添加path 重写过滤器
                FilterDefinition filter = new FilterDefinition();
                filter.setName(original.getName());
                var11 = original.getArgs().entrySet().iterator();

                while(var11.hasNext()) {
                    entry = (Entry)var11.next();
                    value = this.getValueFromExpr(this.evalCtxt, parser, instanceForEval, entry);
                    filter.addArg((String)entry.getKey(), value);
                }

                routeDefinition.getFilters().add(filter);
            }

            return routeDefinition;
        });
    }

	...
}

可以在官方的 GatewaySampleApplication 添加 Eureka 注册中心自行调试：

// 开启Eureka
@EnableDiscoveryClient 
public class GatewaySampleApplication {
    // ... 省略其他代码
  
    @Bean
    public RouteDefinitionLocator discoveryClientRouteDefinitionLocator(DiscoveryClient discoveryClient) {
        return new DiscoveryClientRouteDefinitionLocator(discoveryClient);
    }
}

当然要自己加入 Eureka 依赖以及配置文件

1.4.4 CachingRouteDefinitionLocator

public class CachingRouteDefinitionLocator implements RouteDefinitionLocator, ApplicationListener<RefreshRoutesEvent> {
    private final RouteDefinitionLocator delegate;
    private final Flux<RouteDefinition> routeDefinitions;
    // 收集Route
    private final Map<String, List> cache = new HashMap();

    public CachingRouteDefinitionLocator(RouteDefinitionLocator delegate) {
        this.delegate = delegate;
        FluxCacheBuilderMapMiss var10001 = CacheFlux.lookup(this.cache, "routeDefs", RouteDefinition.class);
        RouteDefinitionLocator var10002 = this.delegate;
        var10002.getClass();
        this.routeDefinitions = var10001.onCacheMissResume(var10002::getRouteDefinitions);
    }

    public Flux<RouteDefinition> getRouteDefinitions() {
        return this.routeDefinitions;
    }

    public Flux<RouteDefinition> refresh() {
        this.cache.clear();
        return this.routeDefinitions;
    }

    public void onApplicationEvent(RefreshRoutesEvent event) {
        this.refresh();
    }

    /** @deprecated */
    @Deprecated
    void handleRefresh() {
        this.refresh();
    }
}

1.4.5 CompositeRouteDefinitionLocator

组合多种 RouteDefinitionLocator 的实现，为 RouteDefinitionRouteLocator 提供统一入口。

public class CompositeRouteDefinitionLocator implements RouteDefinitionLocator {
	// RouteDefinitionLocator 数组
    private final Flux<RouteDefinitionLocator> delegates;

    public CompositeRouteDefinitionLocator(Flux<RouteDefinitionLocator> delegates) {
        this.delegates = delegates;
    }

	// 将组合的 delegates 的路由定义全部返回。
    public Flux<RouteDefinition> getRouteDefinitions() {
        return this.delegates.flatMap(RouteDefinitionLocator::getRouteDefinitions);
    }
}

到此为止外部化的配置的多种方式全部解析完毕。接下来我们来看下编程方式。

2、编程方式

// org.springframework.cloud.gateway.sample.GatewaySampleApplication
@SpringBootConfiguration
@EnableAutoConfiguration
@Import(AdditionalRoutesImportSelector.class)
public class GatewaySampleApplication {

	public static final String HELLO_FROM_FAKE_ACTUATOR_METRICS_GATEWAY_REQUESTS = "hello from fake /actuator/metrics/gateway.requests";

	@Value("${test.uri:http://httpbin.org:80}")
	String uri;

	public static void main(String[] args) {
		SpringApplication.run(GatewaySampleApplication.class, args);
	}

	@Bean
	public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
		// @formatter:off
		// String uri = "http://httpbin.org:80";
		// String uri = "http://localhost:9080";
		// ① RouteLocatorBuilder 可以构建多个路由信息。
		return builder.routes()
				// ② 指定了 Predicates，这里包含两个：
				// 请求头Host需要匹配**.abc.org，通过 HostRoutePredicateFactory 产生。
				// 请求路径需要匹配/anything/png，通过 PathRoutePredicateFactory 产生。
				.route(r -> r.host("**.abc.org").and().path("/anything/png")
					// ③ 指定了一个 Filter，下游服务响应后添加响应头X-TestHeader:foobar，
					// 通过 AddResponseHeaderGatewayFilterFactory 产生。
					.filters(f ->
							f.prefixPath("/httpbin")
									.addResponseHeader("X-TestHeader", "foobar"))
					 // ④ 指定路由转发的目的地 uri。
					.uri(uri)
				)
				.route("read_body_pred", r -> r.host("*.readbody.org")
						.and().readBody(String.class,
										s -> s.trim().equalsIgnoreCase("hi"))
					.filters(f -> f.prefixPath("/httpbin")
							.addResponseHeader("X-TestHeader", "read_body_pred")
					).uri(uri)
				)
				.route("rewrite_request_obj", r -> r.host("*.rewriterequestobj.org")
					.filters(f -> f.prefixPath("/httpbin")
							.addResponseHeader("X-TestHeader", "rewrite_request")
							.modifyRequestBody(String.class, Hello.class, MediaType.APPLICATION_JSON_VALUE,
									(exchange, s) -> {
										return Mono.just(new Hello(s.toUpperCase()));
									})
					).uri(uri)
				)
				.route("rewrite_request_upper", r -> r.host("*.rewriterequestupper.org")
					.filters(f -> f.prefixPath("/httpbin")
							.addResponseHeader("X-TestHeader", "rewrite_request_upper")
							.modifyRequestBody(String.class, String.class,
									(exchange, s) -> {
										return Mono.just(s.toUpperCase() + s.toUpperCase());
									})
					).uri(uri)
				)
				.route("rewrite_response_upper", r -> r.host("*.rewriteresponseupper.org")
					.filters(f -> f.prefixPath("/httpbin")
							.addResponseHeader("X-TestHeader", "rewrite_response_upper")
							.modifyResponseBody(String.class, String.class,
									(exchange, s) -> {
										return Mono.just(s.toUpperCase());
									})
					).uri(uri)
				)
				.route("rewrite_empty_response", r -> r.host("*.rewriteemptyresponse.org")
					.filters(f -> f.prefixPath("/httpbin")
							.addResponseHeader("X-TestHeader", "rewrite_empty_response")
							.modifyResponseBody(String.class, String.class,
									(exchange, s) -> {
										if (s == null) {
											return Mono.just("emptybody");
										}
										return Mono.just(s.toUpperCase());
									})

					).uri(uri)
				)
				.route("rewrite_response_fail_supplier", r -> r.host("*.rewriteresponsewithfailsupplier.org")
					.filters(f -> f.prefixPath("/httpbin")
							.addResponseHeader("X-TestHeader", "rewrite_response_fail_supplier")
							.modifyResponseBody(String.class, String.class,
									(exchange, s) -> {
										if (s == null) {
											return Mono.error(new IllegalArgumentException("this should not happen"));
										}
										return Mono.just(s.toUpperCase());
									})
					).uri(uri)
				)
				.route("rewrite_response_obj", r -> r.host("*.rewriteresponseobj.org")
					.filters(f -> f.prefixPath("/httpbin")
							.addResponseHeader("X-TestHeader", "rewrite_response_obj")
							.modifyResponseBody(Map.class, String.class, MediaType.TEXT_PLAIN_VALUE,
									(exchange, map) -> {
										Object data = map.get("data");
										return Mono.just(data.toString());
									})
							.setResponseHeader("Content-Type", MediaType.TEXT_PLAIN_VALUE)
					).uri(uri)
				)
				.route(r -> r.path("/image/webp")
					.filters(f ->
							f.prefixPath("/httpbin")
									.addResponseHeader("X-AnotherHeader", "baz"))
					.uri(uri)
				)
				.route(r -> r.order(-1)
					.host("**.throttle.org").and().path("/get")
					.filters(f -> f.prefixPath("/httpbin")
									.filter(new ThrottleGatewayFilter()
									.setCapacity(1)
									.setRefillTokens(1)
									.setRefillPeriod(10)
									.setRefillUnit(TimeUnit.SECONDS)))
					.uri(uri)
				)
				// ⑤ 创建RouteLocator实例
				.build();
		// @formatter:on
	}

	@Bean
	public RouterFunction<ServerResponse> testFunRouterFunction() {
		RouterFunction<ServerResponse> route = RouterFunctions.route(RequestPredicates.path("/testfun"),
				request -> ServerResponse.ok().body(BodyInserters.fromValue("hello")));
		return route;
	}

	@Bean
	public RouterFunction<ServerResponse> testWhenMetricPathIsNotMeet() {
		RouterFunction<ServerResponse> route = RouterFunctions
				.route(RequestPredicates.path("/actuator/metrics/gateway.requests"), request -> ServerResponse.ok()
						.body(BodyInserters.fromValue(HELLO_FROM_FAKE_ACTUATOR_METRICS_GATEWAY_REQUESTS)));
		return route;
	}

	static class Hello {
		String message;

		Hello() {
		}

		Hello(String message) {
			this.message = message;
		}

		public String getMessage() {
			return message;
		}

		public void setMessage(String message) {
			this.message = message;
		}
	}

}

① 使用 Builder 模式构建 Route
② 创建 Predicates
③ 创建 Filter
④ 需要转发的目的地 uri
⑤ 创建 RouteLocator 实例

// org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder.Builder#build
public RouteLocator build() {
    return () -> {
        return Flux.fromIterable(this.routes).map((routeBuilder) -> {
            return routeBuilder.build(); // ①
        });
    };
}

// RouteLocator 是 Route 集合
public interface RouteLocator {
    Flux<Route> getRoutes();
}

上面 build 方法返回的是 RouteLocator 对象，它是 Route 的集合所以上面 ① 中的 build 方法就是对应的 Route。

public Route build() {
    Assert.notNull(this.id, "id can not be null");
    Assert.notNull(this.uri, "uri can not be null");
    AsyncPredicate<ServerWebExchange> predicate = this.getPredicate();
    Assert.notNull(predicate, "predicate can not be null");
    return new Route(this.id, this.uri, this.order, predicate, this.gatewayFilters);
}

下面这个就是我们最重要的 Route 数据模型了，我们来看下是如何设计的吧。

public class Route implements Ordered {
	// id，标识符，区别于其他 Route。
    private final String id;
    // destination uri，路由指向的目的地 uri，即客户端请求最终被转发的目的地。
    private final URI uri;
    // order，用于多个 Route 之间的排序，数值越小排序越靠前，匹配优先级越高。
    private final int order;
    // predicate，谓语，表示匹配该 Route 的前置条件，即满足相应的条件才会被路由到目的地 uri。
    private final AsyncPredicate<ServerWebExchange> predicate;
    // gateway filters，过滤器用于处理切面逻辑，如路由转发前修改请求头等。
    private final List<GatewayFilter> gatewayFilters;

	...
}

到这里，外部化配置的 Route、Predicate、Filter 会被映射成 RouteDefinition、FilterDefinition、PredicateDefinition，而编码方式会被映射成 Route、AsyncPredicate 、GatewayFilter。

有时候我们可能又有外部化配置又有编码方式的配置，那么这时候就需要有一个转换。那接下来就看一下 Gateway 是如何转换的。

四、RouteDefinitionRouteLocator

这里将 RouteDefinitionRouteLocator 单独作为一小节来说，RouteDefinitionRouteLocator 将外部化配置的 RouteDefinition、FilterDefinition、PredicateDefinition 转换成 Route、AsyncPredicate、GatewayFilter。

上一篇我们讲到的核心配置类 GatewayAutoConfiguration，给我提供了分析的入口，代码如下：

// ① GatewayProperties 
// ② RouteDefinitionLocator 
@Bean
public RouteLocator routeDefinitionRouteLocator(GatewayProperties properties, List<GatewayFilterFactory> GatewayFilters, List<RoutePredicateFactory> predicates, RouteDefinitionLocator routeDefinitionLocator, @Qualifier("webFluxConversionService") ConversionService conversionService) {
	// ③ 这里进行转换
    return new RouteDefinitionRouteLocator(routeDefinitionLocator, predicates, GatewayFilters, properties, conversionService);
}

1、①、② 在上面外部化配置讲过，这里就不重复阐述了。

2、③ 外部化配置进行转换，RouteDefinitionRouteLocator 是 RouteLocator 的实现

public class RouteDefinitionRouteLocator implements RouteLocator, BeanFactoryAware, ApplicationEventPublisherAware {
    protected final Log logger = LogFactory.getLog(this.getClass());
    public static final String DEFAULT_FILTERS = "defaultFilters";
    // RouteDefinition Locator，一个 RouteDefinitionLocator 对象。
    private final RouteDefinitionLocator routeDefinitionLocator;
    private final ConversionService conversionService;
    /**
   	 * predicates factories，Predicate 工厂列表，会被映射成 key 为 name, value 为 factory 的 Map。
     * 可以猜想出 gateway 是如何根据 PredicateDefinition 中定义的 name 来匹配到相对应的 factory 了。
     * key ：{@link RoutePredicateFactory#name()}
     */
    private final Map<String, RoutePredicateFactory> predicates = new LinkedHashMap();
    /**
     * filter factories，Gateway Filter 工厂列表，同样会被映射成 key 为 name, value 为 factory 的 Map。
  	 * key ：{@link GatewayFilterFactory#name()}
   	 */
    private final Map<String, GatewayFilterFactory> gatewayFilterFactories = new HashMap();
    // gateway properties，外部化配置类。
    private final GatewayProperties gatewayProperties;
    private final SpelExpressionParser parser = new SpelExpressionParser();
    private BeanFactory beanFactory;
    private ApplicationEventPublisher publisher;
    @Autowired
    private Validator validator;

    public RouteDefinitionRouteLocator(RouteDefinitionLocator routeDefinitionLocator, List<RoutePredicateFactory> predicates, List<GatewayFilterFactory> gatewayFilterFactories, GatewayProperties gatewayProperties, ConversionService conversionService) {
    	// 设置 RouteDefinitionLocator
        this.routeDefinitionLocator = routeDefinitionLocator;
        this.conversionService = conversionService;
        // ① 初始化 RoutePredicateFactory
        this.initFactories(predicates);
        // ② 初始化 gatewayFilterFactories
        gatewayFilterFactories.forEach((factory) -> {
            GatewayFilterFactory var10000 = (GatewayFilterFactory)this.gatewayFilterFactories.put(factory.name(), factory);
        });
        // 设置 GatewayProperties
        this.gatewayProperties = gatewayProperties;
    }

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

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

	// ③ 实现 RouteLocator 的 getRoutes() 方法 获取 route
    public Flux<Route> getRoutes() {
    	// 调用 convertToRoute 方法将 RouteDefinition 转换成 Route。
        return this.routeDefinitionLocator.getRouteDefinitions().map(this::convertToRoute).map((route) -> {
            if (this.logger.isDebugEnabled()) {
                this.logger.debug("RouteDefinition matched: " + route.getId());
            }

            return route;
        });
    }

	...
}

2.1 ① 初始化 RoutePredicateFactory

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 (this.logger.isInfoEnabled()) {
            this.logger.info("Loaded RoutePredicateFactory [" + key + "]");
        }

    });
}

2.2 ② 初始化 gatewayFilterFactories

// FilterDefinition 转换成 GatewayFilter
private List<GatewayFilter> getFilters(RouteDefinition routeDefinition) {
    List<GatewayFilter> filters = new ArrayList();
    // ① 处理 GatewayProperties 中定义的默认的 FilterDefinition，转换成 GatewayFilter。
    if (!this.gatewayProperties.getDefaultFilters().isEmpty()) {
        filters.addAll(this.loadGatewayFilters("defaultFilters", this.gatewayProperties.getDefaultFilters()));
    }
	// ② 将 RouteDefinition 中定义的 FilterDefinition 转换成 GatewayFilter。
    if (!routeDefinition.getFilters().isEmpty()) {
        filters.addAll(this.loadGatewayFilters(routeDefinition.getId(), routeDefinition.getFilters()));
    }
	// ③ 对 GatewayFilter 进行排序，排序的详细逻辑请查阅 spring 中的 Ordered 接口。
    AnnotationAwareOrderComparator.sort(filters);
    return filters;
}

2.3 ③ 实现 RouteLocator 的 getRoutes() 方法获取 Route，真正转换的方法

public Flux<Route> getRoutes() {
	// 调用 convertToRoute 方法将 RouteDefinition 转换成 Route。
    return this.routeDefinitionLocator.getRouteDefinitions().map(this::convertToRoute).map((route) -> {
        if (this.logger.isDebugEnabled()) {
            this.logger.debug("RouteDefinition matched: " + route.getId());
        }

        return route;
    });
}

private Route convertToRoute(RouteDefinition routeDefinition) {
	// 2.3.1 将 PredicateDefinition 转换成 AsyncPredicate。
    AsyncPredicate<ServerWebExchange> predicate = this.combinePredicates(routeDefinition);
    // 2.3.2 将 FilterDefinition 转换成 GatewayFilter。
    List<GatewayFilter> gatewayFilters = this.getFilters(routeDefinition);
    // 2.3.3 根据 1 和 2 两步骤定义的变量生成 Route 对象。
    return ((AsyncBuilder)Route.async(routeDefinition).asyncPredicate(predicate).replaceFilters(gatewayFilters)).build();
}

2.3.1 将 PredicateDefinition 转换成 AsyncPredicate

private AsyncPredicate<ServerWebExchange> combinePredicates(RouteDefinition routeDefinition) {
    List<PredicateDefinition> predicates = routeDefinition.getPredicates();
    // ① 调用 lookup 方法，将列表中第一个 PredicateDefinition 转换成 AsyncPredicate。
    AsyncPredicate<ServerWebExchange> predicate = this.lookup(routeDefinition, (PredicateDefinition)predicates.get(0));

    AsyncPredicate found;
    // ② 循环调用，将列表中每一个 PredicateDefinition 都转换成 AsyncPredicate。
    // ③ 应用and操作，将所有的 AsyncPredicate 组合成一个 AsyncPredicate 对象。
    for(Iterator var4 = predicates.subList(1, predicates.size()).iterator(); var4.hasNext(); predicate = predicate.and(found)) {
        PredicateDefinition andPredicate = (PredicateDefinition)var4.next();
        found = this.lookup(routeDefinition, andPredicate);
    }

    return predicate;
}

2.3.2 将 FilterDefinition 转换成 GatewayFilter

// FilterDefinition 转换成 GatewayFilter
private List<GatewayFilter> getFilters(RouteDefinition routeDefinition) {
    List<GatewayFilter> filters = new ArrayList();
    // ① 处理 GatewayProperties 中定义的默认的 FilterDefinition，转换成 GatewayFilter。
    if (!this.gatewayProperties.getDefaultFilters().isEmpty()) {
        filters.addAll(this.loadGatewayFilters("defaultFilters", this.gatewayProperties.getDefaultFilters()));
    }
	// ② 将 RouteDefinition 中定义的 FilterDefinition 转换成 GatewayFilter。
    if (!routeDefinition.getFilters().isEmpty()) {
        filters.addAll(this.loadGatewayFilters(routeDefinition.getId(), routeDefinition.getFilters()));
    }
	// ③ 对 GatewayFilter 进行排序，排序的详细逻辑请查阅 spring 中的 Ordered 接口。
    AnnotationAwareOrderComparator.sort(filters);
    return filters;
}

2.3.3 根据 2.3.1 和 2.3.2 两步骤定义的变量生成 Route 对象

public Route build() {
    Assert.notNull(this.id, "id can not be null");
    Assert.notNull(this.uri, "uri can not be null");
    AsyncPredicate<ServerWebExchange> predicate = this.getPredicate();
    Assert.notNull(predicate, "predicate can not be null");
    return new Route(this.id, this.uri, this.order, predicate, this.gatewayFilters);
}