Gateway（一）初始化

//org.springframework.cloud.gateway.sample.GatewaySampleApplication
@SpringBootConfiguration 
@EnableAutoConfiguration //自动装配
@Import(AdditionalRoutes.class)
public class GatewaySampleApplication {
	public static void main(String[] args) {
		SpringApplication.run(GatewaySampleApplication.class, args);
	}
}

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayAutoConfiguration,\ //重点关注
org.springframework.cloud.gateway.config.GatewayLoadBalancerClientAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayNoLoadBalancerClientAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayMetricsAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration,\
org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration,\
org.springframework.cloud.gateway.config.SimpleUrlHandlerMappingGlobalCorsAutoConfiguration,\
org.springframework.cloud.gateway.config.GatewayReactiveLoadBalancerClientAutoConfiguration

@Configuration
//通过 spring.cloud.gateway.enabled 配置网关的开启与关闭。 默认是 打开的
@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)
@EnableConfigurationProperties
@AutoConfigureBefore({ HttpHandlerAutoConfiguration.class,
		WebFluxAutoConfiguration.class })
@AutoConfigureAfter({ GatewayLoadBalancerClientAutoConfiguration.class,
		GatewayClassPathWarningAutoConfiguration.class })
@ConditionalOnClass(DispatcherHandler.class)
public class GatewayAutoConfiguration {

  //用于构建Route的 Builder
	@Bean
	public RouteLocatorBuilder routeLocatorBuilder(
			ConfigurableApplicationContext context) {
		return new RouteLocatorBuilder(context);
	}

  //RouteDefinitionLocator 的实现类，用于从配置文件(Properties,yml) 获取Route配置
	@Bean
	@ConditionalOnMissingBean
	public PropertiesRouteDefinitionLocator propertiesRouteDefinitionLocator(
			GatewayProperties properties) {
		//RouteDefinitionLocator 的实现类，RouteDefinition 信息来自 GatewayProperties。
		return new PropertiesRouteDefinitionLocator(properties);
	}

  //RouteDefinitionLocator 的实现类，基于内存的存储器( 例如，内存 / Redis / MySQL 等 )读取、保存、删除路由配置。
	@Bean
	@ConditionalOnMissingBean(RouteDefinitionRepository.class)
	public InMemoryRouteDefinitionRepository inMemoryRouteDefinitionRepository() {
		return new InMemoryRouteDefinitionRepository();
	}

	/*
	声明 beanrouteDefinitionLocator，使用 CompositeRouteDefinitionLocator 实现，它组合了多个 RouteDefinitionLocator 实例。
	这给用户（开发者）提供了可扩展的余地，用户可以根据需要扩展自己的 RouteDefinitionLocator，比如 RouteDefinition 可源自数据库。
	 */
	@Bean
	@Primary
	public RouteDefinitionLocator routeDefinitionLocator(
			List<RouteDefinitionLocator> routeDefinitionLocators) {
		return new CompositeRouteDefinitionLocator(
				Flux.fromIterable(routeDefinitionLocators));
	}

  //基于 RouteDefinitionLocator 的 RouteLocator 实现类。RouteDefinitionRouteLocator 从 RouteDefinitionLocator 获取 RouteDefinition ，转换成 Route
	@Bean
	public RouteLocator routeDefinitionRouteLocator(GatewayProperties properties,
			List<GatewayFilterFactory> gatewayFilters,
			List<RoutePredicateFactory> predicates,
			RouteDefinitionLocator routeDefinitionLocator,
			@Qualifier("webFluxConversionService") ConversionService conversionService) {
		return new RouteDefinitionRouteLocator(routeDefinitionLocator, predicates,
				gatewayFilters, properties, conversionService);
	}

  //监听route的更新
	@Bean
	public RouteRefreshListener routeRefreshListener(
			ApplicationEventPublisher publisher) {
		return new RouteRefreshListener(publisher);
	}

  //FilteringWebHandler 通过创建请求对应的 Route 对应的 GatewayFilterChain 进行处理。
	@Bean
	public FilteringWebHandler filteringWebHandler(List<GlobalFilter> globalFilters) {
		return new FilteringWebHandler(globalFilters);
	}

  
  //用于查找匹配到 Route ，并进行处理
	@Bean
	public RoutePredicateHandlerMapping routePredicateHandlerMapping(
			FilteringWebHandler webHandler, RouteLocator routeLocator,
			GlobalCorsProperties globalCorsProperties, Environment environment) {
		return new RoutePredicateHandlerMapping(webHandler, routeLocator,
				globalCorsProperties, environment);
	}

	//是 Spring cloud gateway 模块提供的外部化配置类。
	@Bean
	public GatewayProperties gatewayProperties() {
		return new GatewayProperties();
	}
  
  //...省略一些内置的Filter 和 Predicate

	//初始化 NettyConfiguration  Netty配置类
	@Configuration
	@ConditionalOnClass(HttpClient.class)
	protected static class NettyConfiguration {

		@Bean
		@ConditionalOnProperty(name = "spring.cloud.gateway.httpserver.wiretap")
		public NettyWebServerFactoryCustomizer nettyServerWiretapCustomizer(
				Environment environment, ServerProperties serverProperties) {
			return new NettyWebServerFactoryCustomizer(environment, serverProperties) {
				@Override
				public void customize(NettyReactiveWebServerFactory factory) {
					factory.addServerCustomizers(httpServer -> httpServer.wiretap(true));
					super.customize(factory);
				}
			};
		}

		//创建一个类型为 reactor.ipc.netty.http.client.HttpClient 的 Bean 对象。该 HttpClient 使用 Netty 实现的 Client 。
		@Bean
		@ConditionalOnMissingBean
		public HttpClient gatewayHttpClient(HttpClientProperties properties) {

			// configure pool resources
			HttpClientProperties.Pool pool = properties.getPool();

			ConnectionProvider connectionProvider;
			if (pool.getType() == DISABLED) {
				connectionProvider = ConnectionProvider.newConnection();
			}
			else if (pool.getType() == FIXED) {
				connectionProvider = ConnectionProvider.fixed(pool.getName(),
						pool.getMaxConnections(), pool.getAcquireTimeout());
			}
			else {
				connectionProvider = ConnectionProvider.elastic(pool.getName());
			}

			HttpClient httpClient = HttpClient.create(connectionProvider)
					.tcpConfiguration(tcpClient -> {

						if (properties.getConnectTimeout() != null) {
							tcpClient = tcpClient.option(
									ChannelOption.CONNECT_TIMEOUT_MILLIS,
									properties.getConnectTimeout());
						}

						// configure proxy if proxy host is set.
						HttpClientProperties.Proxy proxy = properties.getProxy();

						if (StringUtils.hasText(proxy.getHost())) {

							tcpClient = tcpClient.proxy(proxySpec -> {
								ProxyProvider.Builder builder = proxySpec
										.type(ProxyProvider.Proxy.HTTP)
										.host(proxy.getHost());

								PropertyMapper map = PropertyMapper.get();

								map.from(proxy::getPort).whenNonNull().to(builder::port);
								map.from(proxy::getUsername).whenHasText()
										.to(builder::username);
								map.from(proxy::getPassword).whenHasText()
										.to(password -> builder.password(s -> password));
								map.from(proxy::getNonProxyHostsPattern).whenHasText()
										.to(builder::nonProxyHosts);
							});
						}
						return tcpClient;
					});

			HttpClientProperties.Ssl ssl = properties.getSsl();
			if (ssl.getTrustedX509CertificatesForTrustManager().length > 0
					|| ssl.isUseInsecureTrustManager()) {
				httpClient = httpClient.secure(sslContextSpec -> {
					// configure ssl
					SslContextBuilder sslContextBuilder = SslContextBuilder.forClient();

					X509Certificate[] trustedX509Certificates = ssl
							.getTrustedX509CertificatesForTrustManager();
					if (trustedX509Certificates.length > 0) {
						sslContextBuilder.trustManager(trustedX509Certificates);
					}
					else if (ssl.isUseInsecureTrustManager()) {
						sslContextBuilder
								.trustManager(InsecureTrustManagerFactory.INSTANCE);
					}

					sslContextSpec.sslContext(sslContextBuilder)
							.defaultConfiguration(ssl.getDefaultConfigurationType())
							.handshakeTimeout(ssl.getHandshakeTimeout())
							.closeNotifyFlushTimeout(ssl.getCloseNotifyFlushTimeout())
							.closeNotifyReadTimeout(ssl.getCloseNotifyReadTimeout());
				});
			}

			if (properties.isWiretap()) {
				httpClient = httpClient.wiretap(true);
			}

			return httpClient;
		}
    
    //...省略一些内置的Filter 和 Predicate
}