Spring Cloud 新一代网关：Spring Cloud GateWay

简介

为什么用网关？

Spring Cloud GateWay的核心执行逻辑

示例编写

父pom

依赖项目gateway的pom

application.yml

启动项

启动日志

---

简介

简单点说：Spring Cloud GateWay就像医院里分诊台，将你引导到各个科室

Spring Cloud GateWay提供了一套简单有效的API路由管理方式，是基于Filter(过滤器)的方式提供网关的基本功能

作用：

• 安全验证
• 监控
• 限流
• 熔断
• 重试等

Netflix Zuul 由于Netflix公司迟迟不更新2.0，开发者已经对它失去信心了，反正我是失去了，Spring Cloud GateWay会一步一步的取代Zuul

为什么用网关？

服务网关 = 路由转发 + 过滤器

1、路由转发：接收一切外界请求，转发到后端的微服务上去；

2、过滤器：在服务网关中可以完成一系列的横切功能，例如权限校验、限流以及监控等，这些都可以通过过滤器完成（其实路由转发也是通过过滤器实现的）;

假设你开发一个电商服务，有会员，支付，商品等等服务

• 你会对每个服务都进行鉴权、限流、权限校验等逻辑？
• 每次上线一个服务都要申请域名，配置Nginx等等？
• 每个服务可能用不同的开发语言编写，那么可能会采用不同的协议，例如Dubbo,HTTP等，你也要适配这些协议？
• 商品服务业务量越来越大，需要拆分，那么需要客户端配合改造，这也是非常蛋疼的事情

这个时候网管服务就起作用了，类似Nginx的作用，将所有用户的请求转发给后端的服务器，但网关做的不仅仅只是简单的转发，也会针对流量做一些扩展，比如鉴权、限流、权限、熔断、协议转换、错误码统一、缓存、日志、监控、告警等，这样将通用的逻辑抽出来，由网关统一去做，业务方也能够更专注于业务逻辑，提升迭代的效率。

Spring Cloud GateWay的核心执行逻辑

核心逻辑 = 断言(Predicate:断言是否为true才允许转发) + 路由转发(Route) + 执行过滤链(Filter )

官网提供执行图：

执行流程：

• ① Gateway 接收客户端请求。

• ② 请求与 Predicate 进行匹配，获得到对应的 Route。匹配成功后，才能继续往下执行。

• ③ 请求经过 Filter 过滤器链，执行前置（prev）处理逻辑。

  例如说，修改请求头信息等。

• ④ 请求被 Proxy Filter 转发至目标 URI，并最终获得响应。

  一般来说，目标 URI 是被代理的微服务，如果是在 Spring Cloud 架构中。

• ⑤ 响应经过 Filter 过滤器链，执行后置（post）处理逻辑。

• ⑥ Gateway 返回响应给客户端。

其实，就类似就像SpringMVC 的 DispatcherServlet差不多，只是说 SpringMVC 最终转发到 JVM 进程内的指定方法，而 Gateway 最终转发到远程的目标 URI 

下面是一张更清楚的流程图：

示例编写

父pom

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.cloud.work</groupId>
	<artifactId>work-cloud</artifactId>
	<version>1.0.0-SNAPSHOT</version>
	<packaging>pom</packaging>
	
	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<maven.compiler.source>1.8</maven.compiler.source>
		<maven.compiler.target>1.8</maven.compiler.target>
		<java.version>1.8</java.version>
		<spring-cloud-alibaba.version>2.2.0.RELEASE</spring-cloud-alibaba.version>
		<spring-cloud.version>Hoxton.SR5</spring-cloud.version>
		<spring-boot.version>2.3.0.RELEASE</spring-boot.version>
	</properties>

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>com.alibaba.cloud</groupId>
				<artifactId>spring-cloud-alibaba-dependencies</artifactId>
				<version>${spring-cloud-alibaba.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>${spring-cloud.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
			<dependency>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-dependencies</artifactId>
				<version>${spring-boot.version}</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

	<dependencies>
		<dependency>
			<groupId>com.alibaba.cloud</groupId>
			<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

	<repositories>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
		</repository>
	</repositories>

	<modules>
		<module>cloud-gateway</module>
	</modules>
</project>

依赖项目gateway的pom

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>com.cloud.work</groupId>
		<artifactId>work-cloud</artifactId>
		<version>1.0.0-SNAPSHOT</version>
	</parent>
	<artifactId>cloud-gateway</artifactId>
	
	<dependencies>
        <!-- 引入 Spring Cloud Gateway 相关依赖，使用它作为网关，并实现对其的自动配置 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
        </dependency>
    </dependencies>
</project>

application.yml

server:
  port: 8081

spring:
  cloud:
    # Spring Cloud Gateway 配置项，对应 GatewayProperties 类
    gateway:
      # 路由配置项，对应 RouteDefinition 数组
      routes:
        - id: yudaoyuanma # 路由的编号
          uri: https://www.baidu.com # 路由到的目标地址
          predicates: # 断言，作为路由的匹配条件，对应 RouteDefinition 数组
            - Path=/blog
          filters:
            - StripPrefix=1
        - id: oschina # 路由的编号
          uri: https://www.oschina.net # 路由的目标地址
          predicates: # 断言，作为路由的匹配条件，对应 RouteDefinition 数组
            - Path=/oschina
          filters: # 过滤器，对请求进行拦截，实现自定义的功能，对应 FilterDefinition 数组
            - StripPrefix=1

启动项

package com.cloud.gateway;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class GatewayApplication {

    public static void main(String[] args) {
        SpringApplication.run(GatewayApplication.class, args);
    }
}

启动日志

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.0.RELEASE)

2020-11-29 13:12:34.666  INFO 19664 --- [           main] com.cloud.gateway.GatewayApplication     : No active profile set, falling back to default profiles: default
2020-11-29 13:12:35.535  INFO 19664 --- [           main] o.s.cloud.context.scope.GenericScope     : BeanFactory id=83925bed-0b21-326e-a5b0-784d1d4030ed
2020-11-29 13:12:35.639  INFO 19664 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.client.loadbalancer.reactive.LoadBalancerBeanPostProcessorAutoConfiguration' of type [org.springframework.cloud.client.loadbalancer.reactive.LoadBalancerBeanPostProcessorAutoConfiguration] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2020-11-29 13:12:35.640  INFO 19664 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.client.loadbalancer.reactive.LoadBalancerBeanPostProcessorAutoConfiguration$ReactiveLoadBalancerConfig' of type [org.springframework.cloud.client.loadbalancer.reactive.LoadBalancerBeanPostProcessorAutoConfiguration$ReactiveLoadBalancerConfig] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2020-11-29 13:12:35.644  INFO 19664 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'deferringLoadBalancerExchangeFilterFunction' of type [org.springframework.cloud.client.loadbalancer.reactive.DeferringLoadBalancerExchangeFilterFunction] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2020-11-29 13:12:35.851  WARN 19664 --- [           main] o.s.c.n.a.ArchaiusAutoConfiguration      : No spring.application.name found, defaulting to 'application'
2020-11-29 13:12:35.857  WARN 19664 --- [           main] c.n.c.sources.URLConfigurationSource     : No URLs will be polled as dynamic configuration sources.
2020-11-29 13:12:35.857  INFO 19664 --- [           main] c.n.c.sources.URLConfigurationSource     : To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
2020-11-29 13:12:35.863  WARN 19664 --- [           main] c.n.c.sources.URLConfigurationSource     : No URLs will be polled as dynamic configuration sources.
2020-11-29 13:12:35.863  INFO 19664 --- [           main] c.n.c.sources.URLConfigurationSource     : To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
2020-11-29 13:12:43.204  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [After]
2020-11-29 13:12:43.204  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Before]
2020-11-29 13:12:43.204  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Between]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Cookie]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Header]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Host]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Method]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Path]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Query]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [ReadBodyPredicateFactory]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [RemoteAddr]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [Weight]
2020-11-29 13:12:43.205  INFO 19664 --- [           main] o.s.c.g.r.RouteDefinitionRouteLocator    : Loaded RoutePredicateFactory [CloudFoundryRouteService]
2020-11-29 13:12:43.562  INFO 19664 --- [           main] o.s.s.c.ThreadPoolTaskScheduler          : Initializing ExecutorService 'Nacso-Watch-Task-Scheduler'
2020-11-29 13:12:48.231  INFO 19664 --- [           main] o.s.b.web.embedded.netty.NettyWebServer  : Netty started on port(s): 8888
2020-11-29 13:12:51.969  WARN 19664 --- [           main] c.a.c.n.registry.NacosServiceRegistry    : No service to register for nacos client...
2020-11-29 13:12:52.005  INFO 19664 --- [           main] com.cloud.gateway.GatewayApplication     : Started GatewayApplication in 21.601 seconds (JVM running for 22.549)

使用浏览器，访问 http://127.0.0.1:8888/blog，成功转发到目标 URI https://www.baidu.com，如下图所示：