三分钟了解Spring Cloud Gateway路由转发之自动路由

@Autowired
private RouteDefinitionWriter routeDefinitionWriter;
public void addRoute(String id, String uri, String predicates) {
    RouteDefinition routeDefinition = new RouteDefinition();
    routeDefinition.setId(id);
    routeDefinition.setUri(URI.create(uri));
    routeDefinition.setPredicates(Collections.singletonList(new PredicateDefinition(predicates)));
    routeDefinitionWriter.save(Mono.just(routeDefinition)).subscribe();
}
public void updateRoute(String id, String uri, String predicates) {
    RouteDefinition routeDefinition = new RouteDefinition();
    routeDefinition.setId(id);
    routeDefinition.setUri(URI.create(uri));
    routeDefinition.setPredicates(Collections.singletonList(new PredicateDefinition(predicates)));
    routeDefinitionWriter.delete(Mono.just(routeDefinition.getId())).then(Mono.defer(() -> {
        routeDefinitionWriter.save(Mono.just(routeDefinition)).subscribe();
        return Mono.empty();
    })).subscribe();
}
public void deleteRoute(String id) {
    routeDefinitionWriter.delete(Mono.just(id)).subscribe();
}

spring:
  cloud:
    gateway:
      discovery:
        locator:
          enabled: true
          lower-case-service-id: true

public class RoutePredicateHandlerMapping extends AbstractHandlerMapping {
    private final Map<String, RoutePredicateFactory> predicates; // 路由条件工厂类映射表
    private final GatewayFilterHandlerFilter filterHandlerFilter; // 过滤器处理器
    private final Map<String, Object> globalFilters; // 全局过滤器映射表
    private final RouteDefinitionLocator routeDefinitionLocator; // 路由规则定位器
    public RoutePredicateHandlerMapping(List<RoutePredicateFactory> predicates,
                                        GatewayFilterHandlerFilter filterHandlerFilter,
                                        List<GlobalFilter> globalFilters,
                                        RouteDefinitionLocator routeDefinitionLocator) {
        this.predicates = predicates.stream()
                .collect(Collectors.toMap(RoutePredicateFactory::name, Function.identity())); // 将路由条件工厂类列表转换为路由条件工厂类映射表
        this.filterHandlerFilter = filterHandlerFilter;
        this.globalFilters = globalFilters.stream()
                .collect(Collectors.toMap(GlobalFilter::name, Function.identity())); // 将全局过滤器列表转换为全局过滤器映射表
        this.routeDefinitionLocator = routeDefinitionLocator;
        setOrder(-1); // 设置路由转发的优先级
    }
    @Override
    protected Object getHandlerInternal(ServerHttpRequest request) throws Exception {
        List<RouteDefinition> definitions = this.routeDefinitionLocator.getRouteDefinitions().collectList().block(); // 获取所有路由规则
        if (definitions == null) { // 如果路由规则列表为空，则返回 null
            return null;
        }
        for (RouteDefinition routeDefinition : definitions) { // 遍历所有路由规则
            RoutePredicateFactory predicate = this.predicates.get(routeDefinition.getPredicate().getName());            RoutePredicate routePredicate = predicate.apply(routeDefinition.getPredicate().getArgs()); // 创建路由条件
            if (routePredicate.test(request)) { // 判断请求是否满足路由条件
                Route route = new Route(routeDefinition.getId(), routeDefinition.getUri(), routeDefinition.getFilters()); // 创建路由对象
                List<GatewayFilter> gatewayFilters = new ArrayList<>(routeDefinition.getFilters()); // 获取路由规则中的过滤器
                gatewayFilters.addAll(getGlobalFilters()); // 添加全局过滤器
                FilteringWebHandler filteringWebHandler = new FilteringWebHandler(new DefaultWebHandler(), new GatewayFilterChain(gatewayFilters)); // 创建过滤器链
                return new DefaultWebHandlerAdapter().handle(request, filteringWebHandler); // 返回路由转发处理器
            }
        }
        return null;
    }
    private Collection<Object> getGlobalFilters() {
        return this.globalFilters.values(); // 返回全局过滤器集合
    }
}

public class DiscoveryClientRouteDefinitionLocator implements RouteDefinitionLocator {
    // 服务发现客户端
    private final DiscoveryClient discoveryClient;
    // 路由规则转换器
    private final RouteDefinitionLocator routeDefinitionLocator;
    // 服务过滤器
    private final Predicate<ServiceInstance> predicate;
  // 默认使用所有服务实例
    public DiscoveryClientRouteDefinitionLocator(DiscoveryClient discoveryClient, RouteDefinitionLocator routeDefinitionLocator) {
        this(discoveryClient, routeDefinitionLocator, instance -> true); // 默认使用所有服务实例
    }
  // 第二个构造方法可以指定服务过滤器
    public DiscoveryClientRouteDefinitionLocator(DiscoveryClient discoveryClient, RouteDefinitionLocator routeDefinitionLocator, Predicate<ServiceInstance> predicate) {
        this.discoveryClient = discoveryClient;
        this.routeDefinitionLocator = routeDefinitionLocator;
        this.predicate = predicate;
    }
    @Override
    public Flux<RouteDefinition> getRouteDefinitions() {
        return Flux.fromIterable(getServiceNames()) // 获取所有服务名称
                .flatMap(this::getRoutes) // 遍历每个服务名称，获取该服务的路由规则
                .flatMap(routeDefinitionLocator::getRouteDefinitions) // 转换路由规则
                .doOnNext(route -> logger.debug("RouteDefinition matched: " + route)); // 打印日志
    }
    private List<String> getServiceNames() {
        return discoveryClient.getServices(); // 获取服务名称列表
    }
    private Mono<RouteDefinition> getRoutes(String serviceName) {
        return Mono.just(new RouteDefinition()) // 创建一个新的 RouteDefinition 对象
                .flatMap(routeDefinition -> Flux.fromIterable(getInstances(serviceName))) // 获取该服务的所有实例
                .filter(predicate) // 过滤服务实例
                .map(this::getInstanceRoute) // 将服务实例转换为路由规则
                .doOnNext(route -> logger.debug("RouteDefinition created: " + route)) // 打印日志
                .reduce(new RouteDefinition(), this::mergeRouteDefinitions); // 合并所有路由规则
    }
    private List<ServiceInstance> getInstances(String serviceName) {
        return discoveryClient.getInstances(serviceName); // 获取指定服务的所有实例
    }
    private RouteDefinition getInstanceRoute(ServiceInstance instance) {
        RouteDefinition route = new RouteDefinition(); // 创建一个新的 RouteDefinition 对象
        route.setId(instance.getServiceId()); // 设置路由规则的 ID 为服务名称
        URI uri = instance.getUri(); // 获取服务实例的 URI
        if (uri != null) {
            route.setUri(uri); // 设置路由规则的 URI
        }
        return route;
    }
    private RouteDefinition mergeRouteDefinitions(RouteDefinition route1, RouteDefinition route2) {
        route1.getFilters().addAll(route2.getFilters()); // 合并过滤器
        route1.getPredicates().addAll(route2.getPredicates()); // 合并谓词
        return route1;
    }
}