spring cloud gateway源码(二)获取app信息

一、入口

获取app的信息的方法是在DiscoveryClientRouteDefinitionLocator类型的getRouteDefinitions()方法中：

return Flux.fromIterable(discoveryClient.getServices())
				.map(discoveryClient::getInstances)
				.filter(instances -> !instances.isEmpty())
				.map(instances -> instances.get(0))
				.filter(instance -> {
					Boolean include = includeExpr.getValue(evalCtxt, instance, Boolean.class);
					if (include == null) {
						return false;
					}
					return include;

上面的信息是从discoveryClient属性中获取到的，这个discoveryClient是DiscoveryClientRouteDefinitionLocator类中的一个属性：

二、discoveryClient

关于discoveryClient存储了spring cloud gateway的初始节点services，那么这个节点是怎么读入进来的呢，如下

1、首先discoryClient是在DiscoveryClientRouteDefinitionLocator的构造方法中初始化：

	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() + "_";
		}
	}

2、DiscoveryClientRouteDefinitionLocator是一个bean：

	@Bean
	@ConditionalOnBean(DiscoveryClient.class)
	@ConditionalOnProperty(name = "spring.cloud.gateway.discovery.locator.enabled")
	public DiscoveryClientRouteDefinitionLocator discoveryClientRouteDefinitionLocator(
			DiscoveryClient discoveryClient, DiscoveryLocatorProperties properties) {
		return new DiscoveryClientRouteDefinitionLocator(discoveryClient, properties);
	}

3、其中DiscoveryClient的类型是CompositeDiscoveryClient

	@Bean
	@Primary
	public CompositeDiscoveryClient compositeDiscoveryClient(List<DiscoveryClient> discoveryClients) {
		return new CompositeDiscoveryClient(discoveryClients);
	}

4、其中参数是DiscoveryClient类型的List，ZookeeperDiscoveryClient是其子类：

	@Bean
	@ConditionalOnMissingBean
	// currently means auto-registration is false. That will change when ZookeeperServiceDiscovery is gone
	public ZookeeperDiscoveryClient zookeeperDiscoveryClient(ServiceDiscovery<ZookeeperInstance> serviceDiscovery) {
		return new ZookeeperDiscoveryClient(serviceDiscovery, this.zookeeperDependencies);
	}

5、入参是ServiceDiscovery类型的bean

    public ServiceDiscovery<T> build()
    {
        if ( serializer == null )
        {
            serializer(new JsonInstanceSerializer<T>(payloadClass));
        }
        return new ServiceDiscoveryImpl<T>(client, basePath, serializer, thisInstance, watchInstances);
    }

6、这个bean是通过ServiceDiscoveryBuilder构造的，basePath参数就是我们使用到的services。basePath的设置是在DefaultServiceDiscoveryCustomizer的customize()方法中

	@Override
	public ServiceDiscovery<ZookeeperInstance> customize(ServiceDiscoveryBuilder<ZookeeperInstance> builder) {
		// @formatter:off
		return builder
				.client(this.curator)
				.basePath(this.properties.getRoot())
				.serializer(this.instanceSerializer)
				.build();
		// @formatter:on
	}

7、DefaultServiceDiscoveryCustomizer 此bean的创建方法如下

	@Bean
	@ConditionalOnMissingBean(ServiceDiscoveryCustomizer.class)
	public DefaultServiceDiscoveryCustomizer defaultServiceDiscoveryCustomizer(
			CuratorFramework curator, ZookeeperDiscoveryProperties properties,
			InstanceSerializer<ZookeeperInstance> serializer) {
		return new DefaultServiceDiscoveryCustomizer(curator, properties, serializer);
	}

8、入参properties类型是ZookeeperDiscoveryProperties类型，root值如下：】

private String root = "/services";

至此，就可以看出spring cloud gateway的根目录是/services。