简介

spring cloud loadbalancer是spring自家推出的负载均衡器，可以平替ribbon。

spring cloud loadbalancer + RestClient

RestClient是spring framework 6.1(对应spring boot 3.2)里内置的一个http rest api调用器。相比RestTemplate，RestClient的链式写法使用起来十分流畅丝滑。spring cloud loadbalancer自然也可以与RestClient/RestTemplate进行集成。

使用步骤

1、启动一个服务注册中心（兼容Eureka/Nacos/Consul/K8s等服务注册中心），此处以Eureka为例

依赖：

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

配置：

server:
  port: 8761
eureka:
  client:
    registerWithEureka: false
    fetchRegistry: false
  server:
    waitTimeInMsWhenSyncEmpty: 0
  dashboard:
    enabled: true

代码：

@EnableEurekaServer
@SpringBootApplication
public class EurekaServerApp {

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

}

2、服务提供端（provider）

依赖

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

配置：

server:
  port: 8001

spring:
  application:
    name: spring-httpexchange-server
  cloud:
    loadbalancer:
      enabled: true

eureka:
  client:
    enabled: true
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka

2、调用端（client）

依赖

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

配置：

server:
  port: 8002

spring:
  application:
    name: spring-httpexchange-client
  cloud:
    loadbalancer:
      enabled: true

eureka:
  client:
    enabled: true
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka

配置类代码：

@Configuration
public class HttpClientConfig {

    @LoadBalanced
    @Bean
    RestClient.Builder restClientBuilder() {
        return RestClient.builder();
    }

    @Bean
    public HelloClient helloClient(RestClient.Builder restClientBuilder) {
        return HttpServiceProxyFactory
                .builder()
                .exchangeAdapter(
                        RestClientAdapter.create(
                                restClientBuilder.baseUrl("http://spring-httpexchange-server").build()
                        )
                )
                .build().createClient(HelloClient.class);
    }

}

client调用provider提供的远程http服务的代码无需做任何变化。