深入SpringCloud Gateway底層詳解路由配置定位原理
環(huán)境：SpringCloud Hoxton.SR11
本節(jié)主要了解系統(tǒng)中的謂詞與配置的路由信息是如何進(jìn)行初始化關(guān)聯(lián)生成路由對(duì)象的。每個(gè)謂詞工廠中的Config對(duì)象又是如何被解析配置的。
所有的謂詞工廠中的Config中屬性值是如何被配置的。
在SpringCloud Gateway中的所有謂詞工廠如下：
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命名規(guī)則：XxxRoutePredicateFactory。所有的這些謂詞工廠都是如下的繼承關(guān)系
public class MethodRoutePredicateFactory extends AbstractRoutePredicateFactory<MethodRoutePredicateFactory.Config>
//
public class PathRoutePredicateFactory extends AbstractRoutePredicateFactory<PathRoutePredicateFactory.Config>
// ...所有的謂詞工廠繼承的AbstractRoutePredicateFactory中的泛型都是內(nèi)部類的Config。這個(gè)是如何被配置上值的呢？
6.1 gateway自動(dòng)配置
在下面這個(gè)類中配置了所有的Predicate和Filter。
public class GatewayAutoConfiguration {
@Bean
@ConditionalOnEnabledPredicate
public PathRoutePredicateFactory pathRoutePredicateFactory() {
return new PathRoutePredicateFactory();
}
@Bean
@ConditionalOnEnabledPredicate
public QueryRoutePredicateFactory queryRoutePredicateFactory() {
return new QueryRoutePredicateFactory();
}
@Bean
public RouteLocator routeDefinitionRouteLocator(GatewayProperties properties, List<GatewayFilterFactory> gatewayFilters, List<RoutePredicateFactory> predicates, RouteDefinitionLocator routeDefinitionLocator, ConfigurationService configurationService) {
return new RouteDefinitionRouteLocator(routeDefinitionLocator, predicates,
gatewayFilters, properties, configurationService);
}
@Bean
@Primary
@ConditionalOnMissingBean(name = "cachedCompositeRouteLocator")
public RouteLocator cachedCompositeRouteLocator(List<RouteLocator> routeLocators) {
return new CachingRouteLocator(new CompositeRouteLocator(Flux.fromIterable(routeLocators)));
}
}這里會(huì)層層委托最終查找查找路由定位會(huì)交給RouteDefinitionRouteLocator。CachingRouteLocator起到緩存的作用，將配置的所有路由信息保存。
注意：這里的路由信息是在容器啟動(dòng)后就會(huì)被初始化的。
public class CachingRouteLocator {
private final RouteLocator delegate;
private final Flux<Route> routes;
private final Map<String, List> cache = new ConcurrentHashMap<>();
private ApplicationEventPublisher applicationEventPublisher;
public CachingRouteLocator(RouteLocator delegate) {
this.delegate = delegate;
routes = CacheFlux.lookup(cache, CACHE_KEY, Route.class) .onCacheMissResume(this::fetch);
}
private Flux<Route> fetch() {
return this.delegate.getRoutes().sort(AnnotationAwareOrderComparator.INSTANCE);
}
}實(shí)例化CachingRouteLocator就開始查找所有配置的Route信息。最終的會(huì)委托給RouteDefinitionRouteLocator
RouteDefinitionRouteLocator構(gòu)造函數(shù)中的initFactories方法用來(lái)映射路由工廠的XxxRoutePredicateFactory。
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);
});
}方法中解析每一個(gè)謂詞工廠對(duì)應(yīng)的名稱然后緩存到predicates 集合中。
factory.name()方法解析謂詞名稱。
default String name() {
return NameUtils.normalizeRoutePredicateName(getClass());
}CachingRouteLocator是個(gè)緩存路由定位器，是個(gè)首選的RouteLocator（@Primary）,這里將RouteDefinitionRouteLocator進(jìn)行了合并。
6.2 生成路由對(duì)象Route及Config配置
getRoutes---》convertToRoute---》combinePredicates---》lookup。
根據(jù)上面的自動(dòng)配置也知道了在服務(wù)啟動(dòng)時(shí)就進(jìn)行初始化所有路由信息了。
獲取路由信息
public Flux<Route> getRoutes() {
Flux<Route> routes = this.routeDefinitionLocator.getRouteDefinitions() .map(this::convertToRoute);
routes = routes.onErrorContinue((error, obj) -> {
return routes.map(route -> {
return route;
});
}合并謂詞
private AsyncPredicate<ServerWebExchange> combinePredicates(
RouteDefinition routeDefinition) {
// other code
for (PredicateDefinition andPredicate : predicates.subList(1, predicates.size())) {
AsyncPredicate<ServerWebExchange> found = lookup(routeDefinition, andPredicate);
predicate = predicate.and(found);
}
return predicate;
}進(jìn)入lookup中
private AsyncPredicate<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());
}
// 這里將配置中（yml文件）配置的name，args和謂詞工廠中的Config進(jìn)行關(guān)聯(lián)設(shè)置值
Object config = this.configurationService.with(factory)
.name(predicate.getName())
.properties(predicate.getArgs())
.eventFunction((bound, properties) -> new PredicateArgsEvent(
RouteDefinitionRouteLocator.this, route.getId(), properties))
.bind();
// 最終調(diào)用謂詞工廠（XxxRoutePredicateFactory的apply方法返回RoutePredicate該對(duì)象繼承Predicate）
return factory.applyAsync(config);
}lookup方法中查找，也就是在這里將對(duì)應(yīng)的謂詞Config與RouteDefinition(Predicate)中定義的相對(duì)應(yīng)的屬性關(guān)聯(lián)。
進(jìn)入factory.applyAsync方法
@FunctionalInterface
public interface RoutePredicateFactory<C> extends ShortcutConfigurable, Configurable<C> {
default AsyncPredicate<ServerWebExchange> applyAsync(C config) {
return toAsyncPredicate(apply(config)); // 查看下面的6.2-1圖當(dāng)前apply所有的實(shí)現(xiàn)就是系統(tǒng)內(nèi)部定義的XxxRoutePredicateFactory
}
}
// apply(config)，如這里配置了Path謂詞，那么就會(huì)進(jìn)入PathRoutePredicateFactory中的apply方法
public Predicate<ServerWebExchange> apply(Config config) {
// other code
return new GatewayPredicate() {
public boolean test() {
// todo
}
}
}
// 最后返回一個(gè)異步的謂詞
public static AsyncPredicate<ServerWebExchange> toAsyncPredicate(Predicate<? super ServerWebExchange> predicate) {
Assert.notNull(predicate, "predicate must not be null");
// 這里from就是返回一個(gè)DefaultAsyncPredicate默認(rèn)的異步謂詞
return AsyncPredicate.from(predicate);
}
static AsyncPredicate<ServerWebExchange> from( Predicate<? super ServerWebExchange> predicate) {
return new DefaultAsyncPredicate<>(GatewayPredicate.wrapIfNeeded(predicate));
}圖6.2-1
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最后在combinePredicates方法中將當(dāng)前路由中配置的所有謂詞進(jìn)行了and操作返回。最終回到convertToRoute方法中將當(dāng)前路由中配置的謂詞，過(guò)濾器進(jìn)行了整合包裝返回Route（一個(gè)路由對(duì)象）
public class Route implements Ordered {
private final String id;
private final URI uri;
private final int order;
private final AsyncPredicate<ServerWebExchange> predicate;
private final List<GatewayFilter> gatewayFilters;
private final Map<String, Object> metadata;
}這些Route對(duì)象會(huì)被保存在上面說(shuō)的CachingRouteLocator.routes中。
6.3 定位路由
根據(jù)上面的配置RouteLocator 該類用來(lái)定位路由（查找具體的使用哪個(gè)路由）；當(dāng)一個(gè)請(qǐng)求過(guò)來(lái)會(huì)查找是哪個(gè)路由。
RouteLocator中定義了一個(gè)方法
public interface RouteLocator {
Flux<Route> getRoutes();
}查看這個(gè)getRoutes方法是誰(shuí)調(diào)用的
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看到這個(gè)RoutePredicateHandlerMapping是不是想起了Spring MVC中的HandlerMapping（我們所有的Controller都會(huì)被 RequestMappingHanlderMapping 匹配）。通過(guò)名稱也就知道了該HandlerMapping用來(lái)匹配我們的路由謂詞的誰(shuí)來(lái)處理路由。
接下來(lái)回到前面說(shuō)的RequestMappingHanlderMapping 對(duì)象，當(dāng)我們請(qǐng)求一個(gè)路由地址時(shí)會(huì)執(zhí)行該類中的lookup方法查找路由
protected Mono<Route> lookupRoute(ServerWebExchange exchange) {
// 這里的this.routeLocator就是 CachingRouteLocator對(duì)象
return this.routeLocator.getRoutes()
.concatMap(route -> Mono.just(route).filterWhen(r -> {
exchange.getAttributes().put(GATEWAY_PREDICATE_ROUTE_ATTR, r.getId());
// 過(guò)濾查找符合的路由
return r.getPredicate().apply(exchange);
}).doOnError(e -> logger.error(
"Error applying predicate for route: " + route.getId(),
e)).onErrorResume(e -> Mono.empty()))
.next()
.map(route -> {
if (logger.isDebugEnabled()) {
logger.debug("Route matched: " + route.getId());
}
validateRoute(route, exchange);
return route;
});
}進(jìn)入r.getPredicate().apply(exchange)
public interface AsyncPredicate<T> extends Function<T, Publisher<Boolean>> {
static AsyncPredicate<ServerWebExchange> from(Predicate<? super ServerWebExchange> predicate) {
return new DefaultAsyncPredicate<>(GatewayPredicate.wrapIfNeeded(predicate));
}
class DefaultAsyncPredicate<T> implements AsyncPredicate<T> {
private final Predicate<T> delegate;
public DefaultAsyncPredicate(Predicate<T> delegate) {
this.delegate = delegate;
}
@Override
public Publisher<Boolean> apply(T t) {
return Mono.just(delegate.test(t));
}
@Override
public String toString() {
return this.delegate.toString();
}
}
}這里會(huì)調(diào)用Predicate.test方法（XxxRoutePredicateFactory中的apply方法返回的GatewayPredicate）。
調(diào)用GatewayPredicate.test返回判斷當(dāng)前請(qǐng)求的路由是否匹配。
整體的一個(gè)流程：
1、系統(tǒng)先初始化所有的Predicate(謂詞)和Filter(過(guò)濾器)
2、根據(jù)配置的路由信息（過(guò)濾器，謂詞）包裝返回Route對(duì)象
3、根據(jù)請(qǐng)求路由路徑查找匹配的路由
