一、RouteDefinitionLocator

　　在Spring-Cloud-Gateway的GatewayAutoConfiguration初始化加載中會加載RouteDefinitionLocator（路由定義信息加載器）信息。

//初始化配置路由定義加載器
    @Bean
    @ConditionalOnMissingBean
    public PropertiesRouteDefinitionLocator propertiesRouteDefinitionLocator(GatewayProperties properties) {
        return
 
 new PropertiesRouteDefinitionLocator(properties);
    }

    //初始化存儲路由定義加載器
    @Bean
    @ConditionalOnMissingBean(RouteDefinitionRepository.class)
    public InMemoryRouteDefinitionRepository inMemoryRouteDefinitionRepository() {
        return new InMemoryRouteDefinitionRepository();
    }

     
 
//初始化聚合路由定義加載器
    @Bean
    @Primary
    public RouteDefinitionLocator routeDefinitionLocator(List<RouteDefinitionLocator> routeDefinitionLocators) {
        return new CompositeRouteDefinitionLocator(Flux.fromIterable(routeDefinitionLocators));
    }

查看RouteDefinitionLocator源碼

/**
 * 路由定義信息的定位器，
 * 負責讀取路由配置( org.springframework.cloud.gateway.route.RouteDefinition
 * 子類實現類
 *  1.CachingRouteDefinitionLocator -RouteDefinitionLocator包裝類， 緩存目標RouteDefinitionLocator 為routeDefinitions提供緩存功能
 *  2.CompositeRouteDefinitionLocator -RouteDefinitionLocator包裝類，組合多種 RouteDefinitionLocator 的實現，為 routeDefinitions提供統一入口
 *  3.PropertiesRouteDefinitionLocator-從配置文件(GatewayProperties 例如，YML / Properties 等 ) 讀取RouteDefinition
 *  4.DiscoveryClientRouteDefinitionLocator-從註冊中心( 例如，Eureka / Consul / Zookeeper / Etcd 等 )讀取RouteDefinition
 *  5.RouteDefinitionRepository-從存儲器( 例如，內存 / Redis / MySQL 等 )讀取RouteDefinition
 
*/ public interface RouteDefinitionLocator { /** * 獲取RouteDefinition */ Flux<RouteDefinition> getRouteDefinitions(); }

RouteDefinitionLocator接口只有一個方法getRouteDefinitions，此方法獲取RouteDefinition的核心方法，返回Flux<RouteDefinition>

1.1、PropertiesRouteDefinitionLocator--從配置文件讀取定義定位器

// 從Properties（GatewayProperties）中加載RouteDefinition信息
public class PropertiesRouteDefinitionLocator implements RouteDefinitionLocator {

    // 從appliccation.yml中解析前綴為spring.cloud.gateway的配置
    private final GatewayProperties properties;

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

    @Override
    public Flux<RouteDefinition> getRouteDefinitions() {
        return Flux.fromIterable(this.properties.getRoutes());
    }
}

• GatewayProperties 在GatewayProperties初始化加載，參看：
• Flux 響應式編程

1.2、CachingRouteDefinitionLocator--緩存路由定義定位器

// RouteDefinitionLocator 包裝實現類，實現了路由定義的本地緩存功能
public class CachingRouteDefinitionLocator implements RouteDefinitionLocator {

    //  實際路由定義定位器
    private final RouteDefinitionLocator delegate;
    
    private final Flux<RouteDefinition> routeDefinitions;

    // 路由定義的本地緩存
    private final Map<String, List> cache = new HashMap<>();

    public CachingRouteDefinitionLocator(RouteDefinitionLocator delegate) {
        this.delegate = delegate;
        routeDefinitions = CacheFlux.lookup(cache, "routeDefs", RouteDefinition.class)
                .onCacheMissResume(() -> this.delegate.getRouteDefinitions());

    }
}

1.3、DiscoveryClientRouteDefinitionLocator--配置中心路由定義定位器

public class DiscoveryClientRouteDefinitionLocator implements RouteDefinitionLocator {
     //* 註冊中心客戶端
    private final DiscoveryClient discoveryClient;
     //* 本地配置信息
    private final DiscoveryLocatorProperties properties;
     //* 路由ID前綴
    private final String routeIdPrefix;

    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() + "_";
        }
    }

     //* 通過註冊中心查找服務組裝路由定義信息
    @Override
    public Flux<RouteDefinition> getRouteDefinitions() {
     //...
    }
}

1.4、CompositeRouteDefinitionLocator--各個定位器合並提供統一的getRouteDefinitions方法入口

// 組合多個 RouteDefinitionLocator 的實現，為 routeDefinitions提供統一入口
public class CompositeRouteDefinitionLocator implements RouteDefinitionLocator {

    /**
     * 所有路由定義定位器實例集合
     */
    private final Flux<RouteDefinitionLocator> delegates;

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

    @Override
    public Flux<RouteDefinition> getRouteDefinitions() {
        //將各個RouteDefinitionLocator的getRouteDefinitions合並返回統一的Flux<RouteDefinition>
        return this.delegates.flatMap(RouteDefinitionLocator::getRouteDefinitions);
    }
}

綜合上述

PropertiesRouteDefinitionLocator-->|配置文件加載初始化| 、RouteDefinitionRepository-->|存儲器中加載初始化|、DiscoveryClientRouteDefinitionLocator-->|註冊中心加載初始化|

最終提供通過CompositeRouteDefinitionLocator提供統一的getRouteDefinitions方法

其中GatewayDiscoveryClientAutoConfiguration如下

@Configuration
@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)
@AutoConfigureBefore(GatewayAutoConfiguration.class)
@ConditionalOnClass({DispatcherHandler.class, DiscoveryClient.class})
@EnableConfigurationProperties
public class GatewayDiscoveryClientAutoConfiguration {

    //初始化註冊中心路由定義定位器
    @Bean
    @ConditionalOnBean(DiscoveryClient.class)
    @ConditionalOnProperty(name = "spring.cloud.gateway.discovery.locator.enabled")
    public DiscoveryClientRouteDefinitionLocator discoveryClientRouteDefinitionLocator(
            DiscoveryClient discoveryClient, DiscoveryLocatorProperties properties) {
        return new DiscoveryClientRouteDefinitionLocator(discoveryClient, properties);
    }
}

007-spring cloud gateway-GatewayAutoConfiguration核心配置-RouteDefinition初始化加載