电子商务平台源码请加企鹅求求：三伍三六二四柒二五玖。Spring Cloud Gateway官方教程讲的都是提前在配置文件中配置网关，实际项目中，Spring Cloud Gateway作为微服务的入口，需要尽量避免重启，所以我们需要在Spring Cloud Gateway运行时动态配置网关。

Spring Cloud Gateway自带接口
Spring Cloud Gateway在2018年6月份发布了2.0第一个release版本，官方文档并没有讲如何动态配置，翻看Spring Cloud Gateway源码，发现类org.springframework.cloud.gateway.actuate.GatewayControllerEndpoint中提供了网关配置Restful接口，默认没有启用。在类org.springframework.cloud.gateway.config.GatewayAutoConfiguration中配置了GatewayControllerEndpoint

@Configuration
@ConditionalOnClass(Health.class)
protected static class GatewayActuatorConfiguration {

    @Bean
    @ConditionalOnEnabledEndpoint
    public GatewayControllerEndpoint gatewayControllerEndpoint(RouteDefinitionLocator routeDefinitionLocator, List<GlobalFilter> globalFilters,
                                                            List<GatewayFilterFactory> GatewayFilters, RouteDefinitionWriter routeDefinitionWriter,
                                                            RouteLocator routeLocator) {
        return new GatewayControllerEndpoint(routeDefinitionLocator, globalFilters, GatewayFilters, routeDefinitionWriter, routeLocator);
    }
}

存在org.springframework.boot.actuate.health.Health时启用，添加actuator依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

在gateway项目的application.yml中启用gateway api：

开启actuator管理api，后面要关闭

management:
  endpoints:
    web:
      exposure:
        include:

编码方式
不过这里我们不打算用自带的Restful接口，一来官方文档也没说新增网关参数怎么传，再者我们也不希望在网关暴露这些接口。参照org.springframework.cloud.gateway.actuate.GatewayControllerEndpoint，我们自己编程来动态改变网关。

直接上代码：

import java.net.URI;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.gateway.event.RefreshRoutesEvent;
import org.springframework.cloud.gateway.handler.predicate.PredicateDefinition;
import org.springframework.cloud.gateway.route.RouteDefinition;
import org.springframework.cloud.gateway.route.RouteDefinitionWriter;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.stereotype.Service;
import org.springframework.web.util.UriComponentsBuilder;

import reactor.core.publisher.Mono;

@Service
public class TestGatewayService implements ApplicationEventPublisherAware {

    @Autowired
    private RouteDefinitionWriter     routeDefinitionWriter;
    private ApplicationEventPublisher publisher;

    public String save() {
        RouteDefinition definition = new RouteDefinition();
        PredicateDefinition predicate = new PredicateDefinition();
        Map<String, String> predicateParams = new HashMap<>(8);

        definition.setId("baiduRoute");
        predicate.setName("Path");
        predicateParams.put("pattern", "/baidu");
        predicateParams.put("pathPattern", "/baidu");
        predicate.setArgs(predicateParams);
        definition.setPredicates(Arrays.asList(predicate));
        URI uri = UriComponentsBuilder.fromHttpUrl("http://www.baidu.com").build().toUri();
        definition.setUri(uri);
        routeDefinitionWriter.save(Mono.just(definition)).subscribe();
        this.publisher.publishEvent(new RefreshRoutesEvent(this));
        return "success";
    }

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

代码说明：

1、predicate.setName("Path"); 设置predicat名称，这个名称不是乱起的，Spring会根据名称去查找对应的FilterFactory，目前支持的名称有：After、Before、Between、Cookie、Header、Host、Method、Path、Query、RemoteAddr。
2、definition.setId("baiduRoute"); 设置definition的id，需要全局唯一，默认使用UUID。

3、predicateParams.put("pattern", "/baidu"); 每个Route Predicate的参数不同，详情在官网文档查看对应的Route Predicate配置示例，然而官方文档也很坑，比如Path Route的- Path=/foo/{segment}，把参数给省略了。还是得看源码，在包org.springframework.cloud.gateway.handler.predicate里有Spring Cloud Gateway所有的Predicate，打开对应的RoutePredicateFactory，内部类Config就是该Predicate支持的参数。

4、routeDefinitionWriter.save(Mono.just(definition)).subscribe(); 默认的RouteDefinitionWriter实现类是org.springframework.cloud.gateway.route.InMemoryRouteDefinitionRepository。注意最后一定要调用subscribe()，否则不执行。

至此已编码动态配置了一个基本的网关。