RouteDefinition路由定義，Spring-Cloud-Gateway通過RouteDefinition來轉(zhuǎn)換生成具體的路由信息。RouteDefinition的信息是怎么加載初始化到網(wǎng)關(guān)系統(tǒng)中的，接下來閱讀Spring-Cloud-Gateway的RouteDefinitionLocator（路由定義信息加載器）接口，學(xué)習(xí)RouteDefinition初始化加載

首先查看RouteDefinitionLocator源碼

/**
 * 路由定義信息的定位器，
 * 負(fù)責(zé)讀取路由配置( org.springframework.cloud.gateway.route.RouteDefinition
 * 子類實(shí)現(xiàn)類
 *  1.CachingRouteDefinitionLocator -RouteDefinitionLocator包裝類， 緩存目標(biāo)RouteDefinitionLocator 為routeDefinitions提供緩存功能
 *  2.CompositeRouteDefinitionLocator -RouteDefinitionLocator包裝類，組合多種 RouteDefinitionLocator 的實(shí)現(xiàn)，為 routeDefinitions提供統(tǒng)一入口
 *  3.PropertiesRouteDefinitionLocator-從配置文件(GatewayProperties 例如，YML / Properties 等 ) 讀取RouteDefinition
 *  4.DiscoveryClientRouteDefinitionLocator-從注冊中心( 例如，Eureka / Consul / Zookeeper / Etcd 等 )讀取RouteDefinition
 *  5.RouteDefinitionRepository-從存儲器( 例如，內(nèi)存 / Redis / MySQL 等 )讀取RouteDefinition
 * @author Spencer Gibb
 */
public interface RouteDefinitionLocator {

    /**
     * 獲取RouteDefinition
     * @return
     */
    Flux<RouteDefinition> getRouteDefinitions();
}

RouteDefinitionLocator接口有且僅有一個方法getRouteDefinitions，此方法獲取RouteDefinition的核心方法，返回Flux<RouteDefinition>

RouteDefinitionLocator 類圖如下：

graph TD
RouteDefinitionLocator-->CachingRouteDefinitionLocator
RouteDefinitionLocator-->CompositeRouteDefinitionLocator
RouteDefinitionLocator-->PropertiesRouteDefinitionLocator
RouteDefinitionLocator-->DiscoveryClientRouteDefinitionLocator
RouteDefinitionLocator-->RouteDefinitionRepository

子類功能描述：

• CachingRouteDefinitionLocator：RouteDefinitionLocator包裝類， 緩存目標(biāo)RouteDefinitionLocator 為routeDefinitions提供緩存功能
• CompositeRouteDefinitionLocator -RouteDefinitionLocator包裝類，組合多種 RouteDefinitionLocator 的實(shí)現(xiàn)，為 routeDefinitions提供統(tǒng)一入口
• PropertiesRouteDefinitionLocator-從配置文件(GatewayProperties 例如，YML / Properties 等 ) 讀取RouteDefinition
• RouteDefinitionRepository-從存儲器( 例如，內(nèi)存 / Redis / MySQL 等 )讀取RouteDefinition
• DiscoveryClientRouteDefinitionLocator-從注冊中心( 例如，Eureka / Consul / Zookeeper / Etcd 等

接下來詳細(xì)看子類的源碼分析主要實(shí)現(xiàn)功能

• PropertiesRouteDefinitionLocator

/**
 * 從Properties（GatewayProperties）中加載RouteDefinition信息
 * @author Spencer Gibb
 */
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());
    }
}

PropertiesRouteDefinitionLocator很簡單從GatewayProperties實(shí)例獲取RouteDefinition信息

• GatewayProperties 在GatewayProperties初始化加載文中已詳細(xì)描述
• Flux 響應(yīng)式編程

• CachingRouteDefinitionLocator

/**
 * RouteDefinitionLocator 包裝實(shí)現(xiàn)類，實(shí)現(xiàn)了路由定義的本地緩存功能
 * @author Spencer Gibb
 */
public class CachingRouteDefinitionLocator implements RouteDefinitionLocator {

    /**
     * 實(shí)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());

    }

}   

RouteDefinitionLocator包裝類，緩存目標(biāo)RouteDefinitionLocator 為routeDefinitions提供緩存功能

• DiscoveryClientRouteDefinitionLocator

public class DiscoveryClientRouteDefinitionLocator implements RouteDefinitionLocator {
    /**
     * 注冊中心客戶端
     */
    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() + "_";
        }
    }

    /**
     * 通過注冊中心查找服務(wù)組裝路由定義信息
     * @return
     */
    @Override
    public Flux<RouteDefinition> getRouteDefinitions() {
     ...代碼在根據(jù)注冊中心查找路由詳細(xì)解析

    }
}   

DiscoveryClientRouteDefinitionLocator通過調(diào)用 DiscoveryClient 獲取注冊在注冊中心的服務(wù)列表，生成對應(yīng)的 RouteDefinition 數(shù)組

• CompositeRouteDefinitionLocator

/**
 * 組合多個 RouteDefinitionLocator 的實(shí)現(xiàn)，為 routeDefinitions提供統(tǒng)一入口
 * @author Spencer Gibb
 */
public class CompositeRouteDefinitionLocator implements RouteDefinitionLocator {

    /**
     * 所有路由定義定位器實(shí)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合并返回統(tǒng)一的Flux<RouteDefinition>
        return this.delegates.flatMap(RouteDefinitionLocator::getRouteDefinitions);
    }
}

CompositeRouteDefinitionLocator 的主要作用就是將各個定位器合并提供統(tǒng)一的getRouteDefinitions方法入口

通過子類實(shí)現(xiàn)具體功能可以很清晰的看到定位器加載RouteDefinition整個流程

graph TD
PropertiesRouteDefinitionLocator-->|配置文件加載初始化| CompositeRouteDefinitionLocator
RouteDefinitionRepository-->|存儲器中加載初始化| CompositeRouteDefinitionLocator
DiscoveryClientRouteDefinitionLocator-->|注冊中心加載初始化| CompositeRouteDefinitionLocator

最終提供通過CompositeRouteDefinitionLocator提供統(tǒng)一的
getRouteDefinitions方法

RouteDefinitionLocator實(shí)例的初始化在GatewayAutoConfiguration中已經(jīng)完成

GatewayDiscoveryClientAutoConfiguration

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

    //初始化注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);
    }

GatewayAutoConfiguration

   //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));
    }

在Spring-Cloud-Gateway初始化完成后需要的路由定義加載器已全部實(shí)例化完成，這樣就為路由的加載創(chuàng)建完成了必要的條件。