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背景：本想找个简单例子看下，无奈版本依赖太过复杂，花了点时间。记录下吧

使用Spring Cloud Gateway作为网关服务，Nacos作为注册中心，实现对子服务的负载均衡访问。简单例子。

一、gateway-main-nacos服务端：     

完整pom文件：

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.example</groupId><artifactId>gateway-main-nacos</artifactId><version>1.0.0</version><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.5.4</version><relativePath/> <!-- lookup parent from repository --></parent><dependencies><!-- Spring Cloud Gateway --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-gateway</artifactId></dependency><!-- Nacos Discovery --><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId><version>2021.1</version></dependency><!-- Nacos Config --><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId><version>2021.1</version></dependency><!-- Spring Boot Starter Web --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-loadbalancer</artifactId></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>2020.0.3</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement>
</project>

完整的yml配置文件：

server:port: 8888
spring:application:name: gateway-servicemain:web-application-type: reactivecloud:nacos:discovery:server-addr: localhost:8848 # Nacos 服务器地址namespace:  namespace_xxxconfig:server-addr: localhost:8848 # Nacos 配置中心地址file-extension: yamlgateway:discovery:locator:enabled: trueroutes:- id: neo_routeuri: http://www.ityouknow.compredicates:- Path=/spring-cloud
#     - id: add_request_parameter_route
#       uri: http://localhost:8889
#       filters:
#       - AddRequestParameter=foo, bar
#       predicates:
#         - Method=GET- id: lb_nacosuri: lb://user-service  #会进行服务负载均衡filters:- AddRequestParameter=foo, bar123predicates:- Path=/user/** # 匹配 /user/** 路径的请求- id: lb_nacos01uri: lb://user-servicefilters:- StripPrefix=1 # 去掉前缀 /user01predicates:- Path=/user01/** # 匹配 /user01/** 路径的请求

    GatewayApplication启动类:

package com.neo;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;@SpringBootApplication
@EnableDiscoveryClient
public class GatewayApplication {public static void main(String[] args) {SpringApplication.run(GatewayApplication.class, args);}
}

二、  路由的子服务(可以发布两个服务，达到负载均衡的效果)   

完整pom文件：

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.example</groupId><artifactId>user-service</artifactId><version>1.0.0</version><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.5.4</version><relativePath/> <!-- lookup parent from repository --></parent><dependencies><!-- Spring Boot Starter Web --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- Nacos Discovery --><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId><version>2021.1</version></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-bootstrap</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-loadbalancer</artifactId></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>2020.0.3</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement>
</project>

完整的yml文件：

server:port: 8889spring:application:name: user-service#main:#  web-application-type: reactivecloud:gateway:discovery:locator:enabled: truenacos:discovery:server-addr: localhost:8848 # Nacos 服务器地址namespace:  namespace_xxx  #nacos命名空间，修改为自己定义的config:server-addr: localhost:8848 # Nacos 配置中心地址namespace:  namespace_xxxfile-extension: yaml

子服务启动类:

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;@SpringBootApplication
@EnableDiscoveryClient
public class UserServiceApplication {public static void main(String[] args) {SpringApplication.run(UserServiceApplication.class, args);}
}

对应测试的Controller类：

​
@RestController
public class HelloController {@GetMapping("/hello")public String index() {return "hello world!";}@GetMapping("/user/hello")public String indexUser() {return "hello world user!";}@RequestMapping("/user/foo")public String foo(String foo) {return "hello "+foo+"!";}}​

三、测试

本地启动gateway-main-nacos、user-service、user-service-1。 访问 http://localhost:8888/user/hello，多次访问发现会返回 hello world user! 或者 hello world user,another!。达到负载均衡的效果。

访问这个地址也可以看到同样的效果， http://localhost:8888/user01/hello

两个url不同的路由匹配规则。

四、遇到的问题：
1.#允许bean Service循环依赖
spring.main.allow-circular-references=true

2.#Spring MVC found on classpath, which is incompatible with Spring Cloud Gateway.
#同时使用Spring MVC和Spring Cloud Gateway
spring.main.web-application-type=reactive

3.SpringCloud-Gateway搭配服务注册Nacos进行lb动态路由遇到的问题
高版本的spring-cloud-alibaba-dependencies依赖中去除了ribbon依赖，若想能通过Gateway网关找到对应的微服务，需要引入loadbalancer依赖。

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

参考的文档：http://www.ityouknow.com/springcloud/2019/01/19/spring-cloud-gateway-service.html

源码地址：https://github.com/tracysw/Spring-Cloud-Gateway-Samples