Feign(一)——使用

发表于

Feign是一个声明式的Web Service客户端，它使得编写Web Service客户端变得更加简单。我们只需要使用Feign来创建一个接口并用注解来配置它即可完成。它具备可插拔的注解支持，包括Feign注解和JAX-RX注解。Feign也支持可插拔的编码器和解码器。Spring Cloud为Feign增加了对Spring MVC注解的支持，还整合了Ribbon和Eureka来提供均衡负载的HTTP客户端实现。

下面，通过一个例子来展现Feign如何方便地声明对服务的定义和调用。

  1. 配置pom.xml
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<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
</dependencies>
  1. 在应用主类中通过@EnableFeignClients注解开启Feign功能
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@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class EurekaConsumerFeignApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaConsumerFeignApplication.class, args);
    }
}
  1. 定义服务的接口
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@FeignClient("eureka-client")
public interface ComputeClient {
    @RequestMapping(value = "/add", method = RequestMethod.GET)
    Integer add(@RequestParam(value = "a") Integer a, @RequestParam(value = "b") Integer b);
}
  • 使用@FeignClient("eureka-client")注解来绑定该接口对应的服务
  • 通过Spring MVC的注解来配置eureka-client服务下的具体实现
  1. 在controller层调用上面定义的ComputeClient
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@RestController
public class ComputeController {
    @Autowired
    ComputeClient computeClient;

    @RequestMapping(value = "/add", method = RequestMethod.GET)
    public Integer add(@RequestParam(value = "a") Integer a, @RequestParam(value = "b") Integer b) {
        return computeClient.add(a + 1, b + 1);
    }
}
  1. 配置application.yml
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spring:
  application:
    name: eureka-consumer-feign

server:
  port: 8765

eureka:
  instance:
    hostname: localhost
  client:
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:8761/eureka/

访问http://localhost:8765/add?a=1&b=5，可以得到结果6。

http://blog.didispace.com/springcloud2/