SpringCloudGateway系列（二）处理请求流程

Z时代
2024-01-10
分类：综合

本篇文章主要从源码的角度揭秘Spring Cloud Gateway的加载和怎么处理请求流程。

1.Spring Gateway概述

SpringCloudGateway是Spring官方基于Spring 5.0，Spring Boot 2.0和Project Reactor等技术开发的网关，Spring Cloud Gateway旨在为微服务架构提供一种简单而有效的统一的API路由管理方式。Spring Cloud Gateway作为Spring Cloud生态系中的网关，目标是替代Netflix ZUUL，其不仅提供统一的路由方式，并且基于Filter链的方式提供了网关基本的功能，例如：安全，监控/埋点，和限流等。

2.容器启动过程的简单加载分析

加载的流程主要是spring容器为主，需要大家熟悉spring框架，这里不做过多的分析了。
Spring Cloud Gateway自动装配类在 org.springframework.cloud.gateway.config 包下，我们可以看到四个配置类：
GatewayAutoConfiguration
GatewayClassPathWarningAutoConfiguration
GatewayLoadBalancerClientAutoConfiguration
GatewayRedisAutoConfiguration
它们的初始化顺序如下图：

2.1 GatewayClassPathWarningAutoConfiguration

Spring Cloud Gateway 2.x 基于 Spring WebFlux 实现。

org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration，用于检查项目是否正确导入 spring-boot-starter-webflux 依赖，而不是错误导入 spring-boot-starter-web 依赖。点击查看源代码

2.2 GatewayLoadBalancerClientAutoConfiguration

org.springframework.cloud.gateway.config.GatewayLoadBalancerClientAutoConfiguration ，初始化 LoadBalancerClientFilter ，点击查看源代码

2.3 GatewayRedisAutoConfiguration

org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration ，初始化 RedisRateLimiter 。
RequestRateLimiterGatewayFilterFactory 基于 RedisRateLimiter 实现网关的限流功能

2.4 GatewayAutoConfiguration

org.springframework.cloud.gateway.config.GatewayAutoConfiguration ，Spring Cloud Gateway 核心配置类，初始化如下：
NettyConfiguration
GlobalFilter
FilteringWebHandler
GatewayProperties
PrefixPathGatewayFilterFactory
RoutePredicateFactory
RouteDefinitionLocator
RouteLocator
RoutePredicateHandlerMapping
GatewayControllerEndpoint

组件关系交互如下图：

2.5 网关的开启与关闭

从 GatewayAutoConfiguration 上的注解 @ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true) ，我们可以看出：

通过 spring.cloud.gateway.enabled 配置网关的开启与关闭。
matchIfMissing = true => 网关默认开启。

2.6 初始化 NettyConfiguration

org.springframework.cloud.gateway.config.NettyConfiguration ，Netty 配置类。代码如下：

@Configuration
@ConditionalOnClass({HttpClient.class})
protectedstaticclassNettyConfiguration{
protectedNettyConfiguration(){
        }
@Bean
@ConditionalOnMissingBean
public HttpClient httpClient(@Qualifier("nettyClientOptions") Consumer<? super Builder> options) {
return HttpClient.create(options);
        }
@Bean
public Consumer<? super Builder> nettyClientOptions(HttpClientProperties properties) {
return (opts) -> {
                Ssl ssl = properties.getSsl();
if (ssl.isUseInsecureTrustManager()) {
                    opts.sslSupport((sslContextBuilder) -> {
                        sslContextBuilder.trustManager(InsecureTrustManagerFactory.INSTANCE);
                    });
                }
                Pool pool = properties.getPool();
                PoolResources poolResources;
if (pool.getType() == PoolType.FIXED) {
                    poolResources = PoolResources.fixed(pool.getName(), pool.getMaxConnections(), pool.getAcquireTimeout());
                } else {
                    poolResources = PoolResources.elastic(pool.getName());
                }
                opts.poolResources(poolResources);
                Proxy proxy = properties.getProxy();
if (StringUtils.hasText(proxy.getHost())) {
                    opts.proxy((typeSpec) -> {
                        reactor.ipc.netty.options.ClientProxyOptions.Builder builder = typeSpec.type(reactor.ipc.netty.options.ClientProxyOptions.Proxy.HTTP).host(proxy.getHost());
                        PropertyMapper map = PropertyMapper.get();
                        proxy.getClass();
                        map.from(proxy::getPort).whenNonNull().to(builder::port);
                        proxy.getClass();
                        map.from(proxy::getUsername).whenHasText().to(builder::username);
                        proxy.getClass();
                        map.from(proxy::getPassword).whenHasText().to((password) -> {
                            builder.password((s) -> {
return password;
                            });
                        });
                        proxy.getClass();
                        map.from(proxy::getNonProxyHostsPattern).whenHasText().to(builder::nonProxyHosts);
return builder;
                    });
                }
            };
        }

2.7 初始化 GlobalFilter

代码如下：

@Bean
public RouteToRequestUrlFilter routeToRequestUrlFilter(){
returnnew RouteToRequestUrlFilter();
    }
@Bean
@ConditionalOnBean({DispatcherHandler.class})
public ForwardRoutingFilter forwardRoutingFilter(DispatcherHandler dispatcherHandler){
returnnew ForwardRoutingFilter(dispatcherHandler);
    }
@Bean
public WebSocketService webSocketService(){
returnnew HandshakeWebSocketService();
    }
@Bean
public WebsocketRoutingFilter websocketRoutingFilter(WebSocketClient webSocketClient, WebSocketService webSocketService, ObjectProvider<List<HttpHeadersFilter>> headersFilters){
returnnew WebsocketRoutingFilter(webSocketClient, webSocketService, headersFilters);
    }

2.8初始化 FilteringWebHandler

当所有 org.springframework.cloud.gateway.filter.GlobalFilter 初始化完成时( 包括上面的 NettyRoutingFilter / NettyWriteResponseFilter )，创建一个类型为 org.springframework.cloud.gateway.handler.FilteringWebHandler 的 Bean 对象，代码如下：

@Bean
public FilteringWebHandler filteringWebHandler(List<GlobalFilter> globalFilters){
returnnew FilteringWebHandler(globalFilters);
    }

2.9 初始化 GatewayProperties

创建一个类型为 org.springframework.cloud.gateway.config.GatewayProperties 的 Bean 对象，用于加载配置文件配置的 RouteDefinition / FilterDefinition 。代码如下：

@Bean
public GatewayProperties gatewayProperties(){
returnnew GatewayProperties();
    }

3.0 初始化 PrefixPathGatewayFilterFactory

在链接的【第 288 至 372 行】，创建 org.springframework.cloud.gateway.filter.factory 包下的 org.springframework.cloud.gateway.filter.factory.GatewayFilterFactory 接口的实现们。

3.1 初始化 RoutePredicateFactory

在链接的【第 236 至 284 行】，创建 org.springframework.cloud.gateway.handler.predicate 包下的 org.springframework.cloud.gateway.handler.predicate.RoutePredicateFactory 接口的实现们。

3.2初始化 RouteDefinitionLocator

代码如下：

@Bean
@ConditionalOnMissingBean
public PropertiesRouteDefinitionLocator propertiesRouteDefinitionLocator(GatewayProperties properties){
returnnew PropertiesRouteDefinitionLocator(properties);
    }
@Bean
@ConditionalOnMissingBean({RouteDefinitionRepository.class})
public InMemoryRouteDefinitionRepository inMemoryRouteDefinitionRepository(){
returnnew InMemoryRouteDefinitionRepository();
    }
@Bean
@Primary
public RouteDefinitionLocator routeDefinitionLocator(List<RouteDefinitionLocator> routeDefinitionLocators){
returnnew CompositeRouteDefinitionLocator(Flux.fromIterable(routeDefinitionLocators));
    }

3.3 初始化 RouteLocator

代码如下：

@Bean
public RouteLocator routeDefinitionRouteLocator(GatewayProperties properties, List<GatewayFilterFactory> GatewayFilters, List<RoutePredicateFactory> predicates, RouteDefinitionLocator routeDefinitionLocator){
returnnew RouteDefinitionRouteLocator(routeDefinitionLocator, predicates, GatewayFilters, properties);
    }
@Bean
@Primary
public RouteLocator cachedCompositeRouteLocator(List<RouteLocator> routeLocators){
returnnew CachingRouteLocator(new CompositeRouteLocator(Flux.fromIterable(routeLocators)));
    }

另外，有如下两种方式实现自定义 RouteLocator ：

使用 Routes#locator()#build() 方法，创建 RouteLocator ，例子代码如下：

@Bean
public RouteLocator customRouteLocator(){
//@formatter:off
return Routes.locator()
            .route("test")
                .predicate(host("**.abc.org").and(path("/image/png")))
                .addResponseHeader("X-TestHeader", "foobar")
                .uri("http://httpbin.org:80")
            .route("test2")
                .predicate(path("/image/webp"))
                .add(addResponseHeader("X-AnotherHeader", "baz"))
                .uri("http://httpbin.org:80")
            .build();
////@formatter:on
}

使用 RouteLocatorDsl#gateway() 方法，创建 RouteLocator ，该方式使用 Kotlin 实现，例子代码如下：

@Configuration
classAdditionalRoutes{
@Bean
fun additionalRouteLocator(): RouteLocator = gateway {
        route(id = "test-kotlin") {
            uri("http://httpbin.org:80")
            predicate(host("kotlin.abc.org") and path("/image/png"))
add(addResponseHeader("X-TestHeader", "foobar"))
        }
    }
}

3.4 初始化 RoutePredicateHandlerMapping

创建一个类型为 org.springframework.cloud.gateway.handler.RoutePredicateHandlerMapping 的 Bean 对象，用于查找匹配到 Route ，并进行处理。代码如下：

@Bean
public RoutePredicateHandlerMapping routePredicateHandlerMapping(FilteringWebHandler webHandler, RouteLocator routeLocator){
returnnew RoutePredicateHandlerMapping(webHandler, routeLocator);
    }

3.5初始化 GatewayWebfluxEndpoint

创建一个类型为 org.springframework.cloud.gateway.actuate.GatewayControllerEndpoint 的 Bean 对象，提供管理网关的 HTTP API ，代码如下：

@Configuration
@ConditionalOnClass({Health.class})
protectedstaticclassGatewayActuatorConfiguration{
protectedGatewayActuatorConfiguration(){
        }
@Bean
@ConditionalOnEnabledEndpoint
public GatewayControllerEndpoint gatewayControllerEndpoint(RouteDefinitionLocator routeDefinitionLocator, List<GlobalFilter> globalFilters, List<GatewayFilterFactory> GatewayFilters, RouteDefinitionWriter routeDefinitionWriter, RouteLocator routeLocator){
returnnew GatewayControllerEndpoint(routeDefinitionLocator, globalFilters, GatewayFilters, routeDefinitionWriter, routeLocator);
        }
    }

4. Spring Cloud gateway请求入口分析

不管是Zuul，还是Spring Cloud Gateway还是基于Netty的自研网关，都会把请求进来的Request，或者返回的Response进行包装，转换提取为网关运行的上下文信息，而在Spring Cloud gateway中网关的上下文为ServerWebExchange。

4.1 入口HttpServerRequest和HttpServerResponse转换

Spring Cloud Gateway的请求入口，org.springframework.http.server.reactive.ReactorHttpHandlerAdapter#apply方法

代码来源于spring-web-5.0.4.RELEASE.jar 此方法为Spring Cloud Gateway的请求入口方法，该方法的作用就是把接收到的HttpServerRequest或者最终需要返回的HttpServerResponse，包装转换为ReactorServerHttpRequest和ReactorServerHttpResponse。

4.2 构造Spring Cloud gateway的上下文ServerWebExchange

在org.springframework.web.server.adapter.HttpWebHandlerAdapter的91行，代码如下所示:

createExchange()将ServerHttpRequest ServerHttpResponse构建网关上下文ServerWebExchange。

PS:org.springframework.web.server.handler.WebHandlerDecorator.getDelegate()通过委托的方式获取一系列需要处理的WebHandler.

4.3 进入Filter链

org.springframework.cloud.gateway.handler.FilteringWebHandler#handle方法，即46行，代码如下所示:

4.4 执行Filter链

4.5 Gateway Filter委托为Gloable Filter执行

以上是 SpringCloudGateway系列（二）处理请求流程的全部内容，来源链接： utcz.com/z/515783.html

SpringCloudGateway系列（二）处理请求流程

1.Spring Gateway概述

2.容器启动过程的简单加载分析

2.1 GatewayClassPathWarningAutoConfiguration

2.2 GatewayLoadBalancerClientAutoConfiguration

2.3 GatewayRedisAutoConfiguration

2.4 GatewayAutoConfiguration

2.5 网关的开启与关闭

2.6 初始化 NettyConfiguration

2.7 初始化 GlobalFilter

2.8初始化 FilteringWebHandler

2.9 初始化 GatewayProperties

3.0 初始化 PrefixPathGatewayFilterFactory

3.1 初始化 RoutePredicateFactory

3.2初始化 RouteDefinitionLocator

3.3 初始化 RouteLocator

3.4 初始化 RoutePredicateHandlerMapping

3.5初始化 GatewayWebfluxEndpoint

4. Spring Cloud gateway请求入口分析

4.1 入口HttpServerRequest和HttpServerResponse转换

4.2 构造Spring Cloud gateway的上下文ServerWebExchange

4.3 进入Filter链

4.4 执行Filter链

4.5 Gateway Filter委托为Gloable Filter执行

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