最近项目中用到了很多的远程调用，但是还不准备上微服务，但是feign client提供的对远程调用的封装还是很好用的，所以决定引用。 参考之前写的文章Feign Client without Eureka，发现升级到openfeign 3.1.7后并不能兼容，一直收到异常feign.FeignException$ServiceUnavailable: [503] during [POST] to [XXX]: [Load balancer does not contain an instance for the service XXX]。本文介绍了升级openfeign 3之后的使用方法。

添加依赖: pom.xml

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
        <version>2.7.12</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
        <version>3.1.7</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-loadbalancer</artifactId>
        <version>3.1.6</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

定义Feign接口

• HomeApi

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

@FeignClient(name = "home", path = "/home")
public interface HomeApi {
    @GetMapping("/ping")
    String ping();
}

注意：这里的name = "home"需要与后面配置文件中的home一致

配置文件

• application.yml

# 配置home的URI
spring:
  cloud:
    discovery:
      client:
        simple:
          instances:
            home:
              -
                uri: http://localhost:8081

上面配置文件中home interface的目标地址是一个数组

接口调用

• FeignWithoutEurekaApplication

import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

import javax.annotation.Resource;

@EnableFeignClients
@SpringBootApplication
public class FeignWithoutEurekaApplication implements ApplicationRunner {

    @Resource
    private HomeApi homeApi;

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

    @Override
    public void run(ApplicationArguments args) throws Exception {
        System.out.println(homeApi.ping());
    }
}

注意需要添加注解@EnableFeignClients

执行结果

标准输出中输出

success

常见问题

• feign.FeignException$ServiceUnavailable: [503] during [POST] to [XXX]: [Load balancer does not contain an instance for the service XXX]:
  不能使用老的这种配置

home:
  ribbon:
    listOfServers: http://localhost:8081

而是该用如下配置方法

spring:
  cloud:
    discovery:
      client:
        simple:
          instances:
            home:
              -
                uri: http://localhost:8081

参考

• Feign Client without Eureka