1. HelloWorld

服务中心以及Product微服务继续使用LoadBalance中的HelloWorld，新建一个client作为OpenFeign的例子

1.1 pom.xml

引入openfeign依赖

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

1.2 yml配置

spring:
  application:
    name: open-feign
server:
  port: 8001
  
eureka:
  client:
    service-url:
      defaultZone: http://localhost:3333/eureka/

1.3 开启OpenFeign

@SpringBootApplication
// 开启OpenFeign
@EnableFeignClients
public class FeignClientApplication {

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

}

1.4 创建Product的FeignClient

@FeignClient("product")
public interface ProductFeignClient {

    @GetMapping("/product")
    public String getProduct();
}

1.5 Controller

@RestController
@RequestMapping("/feign")
public class ProductController {
    // 注入ProductFeignClient
    @Autowired
    private ProductFeignClient productFeignClient = null;

    @GetMapping("/product")
    public String getProduct() {
        // product client发起请求
        return productFeignClient.getProduct();
    }
}

HelloWorld简简单单就建好了。启动四个服务，浏览器输入http://localhost:8001/feign/product，即可在浏览器看到5001或者5002。多试几次会发现5001和5002是依次出现的，SpringCloud全家桶使用的自家的LoadBalance实现负载均衡，默认情况下会使用，不用特别配置。