Spring注解之@FeignClient注解使用方法

声明接口时在代码中通过@Resource注入容器之后即可使用。@FeignClient注解的常用属性如下：

• value/name：value和name的作用一样，用于指定FeignClient的名称；如果没有配置url，而且项目使用了Eureka 、nacos或者ribbon，name属性会作为微服务的名称，用于服务发现。反之，只是一个名称。此属性和 spring.application.name 对应。
• url：一般用于调试，作用是指定@FeignClient调用的API地址，而非从服务中心获取。

url和name都可以使用占位符，比如：@FeignClient(name = “your.feign.name",url="${your.feign.url}”)；

• decode404：当发生http 404错误时，如果该字段为true，会调用decoder进行解码；否则，抛出FeignException。
• configuration：Feign配置类，作用是自定义Feign的Encoder、Decoder、LogLevel、Contract。
• fallback：定义容错的处理类，当调用远程接口失败或超时时，会调用对应接口的容错逻辑，fallback指定的类必须实现@FeignClient标记的接口。
• fallbackFactory：工厂类，用于生成fallback类实例，实现每个接口通用的容错逻辑，减少重复的代码。
• path：定义当前FeignClient的统一前缀。
• contextId：为某个接口设置单独的超时，与与config里的属性对应。

添加依赖和启动注解

spring-boot-starter-parent版本是2.5.0，需要添加的maven坐标：

<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId><version>3.0.4-SNAPSHOT</version></dependency>

添加启动注解：

@SpringBootApplication@EnableFeignClients//添加这个注解public class XXXXApplication {  public static void main(String[] args) {SpringApplication.run(XXXXApplication.class, args);  }}

沙场秋点兵

首先，在yaml文件中配置常量self.github.url=https://api.github.com，然后，创建接口类，此接口类定义了需要调用的目标服务中的方法，用Feign官方文档中调用GitHub服务的例子来举例。

import com.swagger.demo.bean.Contributor;import org.springframework.cloud.openfeign.FeignClient;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import java.util.List;//@FeignClient(name = "github", url = "https://api.github.com")@FeignClient(name = "github", url = "${self.github.url}",fallback = GithubFeignClient.MyDefaultFallback.class)public interface GithubFeignClient {@GetMapping(value = "/repos/{owner}/{repo}/contributors")ResponseEntity<List<Contributor>> listContributors(@PathVariable("owner") String owner,@PathVariable("repo") String repo);/** * 容错处理类，当调用失败时，简单返回空list */@Componentclass MyDefaultFallback implements GithubFeignClient {@Overridepublic ResponseEntity<List<Contributor>> listContributors(@PathVariable("owner") String owner,@PathVariable("repo") String repo) {retu new ResponseEntity(new ArrayList<>(), HttpStatus.BAD_REQUEST);}}}// --------- 新增实体类 -----------import lombok.Getter;import lombok.Setter;import lombok.ToString;@Setter@Getter@ToStringpublic class Contributor {/** * 作者 */private String login;/** * 贡献次数 */private int contributions;}

上述被注释的、使用注解@FeignClient的方法也可以使用。MyDefaultFallback类是容错类。下面创建一个controller：

import com.swagger.demo.bean.Contributor;import com.swagger.demo.bean.GithubDTO;import com.swagger.demo.service.GithubFeignClient;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.*;import javax.annotation.Resource;import java.util.List;@RestController@RequestMapping("/github")public class GithubClientController {@Resourceprivate GithubFeignClient githubFeignClient;@PostMapping("/listContributors")public ResponseEntity<List<Contributor>> listContributors(@RequestBody GithubDTO githubDTO) {retu githubFeignClient.listContributors(githubDTO.getOwner(), githubDTO.getFeign());}}

创建idea http类型的测试用例：

### 查询github 贡献者信息POST http://localhost:8087/wiener/github/listContributorsContent-Type: application/json{  "owner": "openFeign",  "feign": "feign"}

启动服务，执行如上测试用例，执行结果如下所示，说明服务调用成功：

last-modified: Tue, 01 Feb 2022 03:52:53 GMTlink: <https://api.github.com/repositories/10981994/contributors?page=2>; rel="next", <https://api.github.com/repositories/10981994/contributors?page=6>; rel="last"[  {"login": "adriancole","contributions": 135  },  {"login": "velo","contributions": 126  },  {"login": "kdavisk6","contributions": 121  },  {"login": "snyk-bot","contributions": 45  },  {"login": "quidryan","contributions": 43  },  {"login": "rspieldenner","contributions": 14  },  {"login": "davidmc24","contributions": 12  },  {"login": "radio-rogal","contributions": 12  },  {"login": "ahus1","contributions": 6  },  {"login": "spencergibb","contributions": 5  },  {"login": "ashleyfrieze","contributions": 5  },  {"login": "allenxwang","contributions": 5  },  {"login": "gimbimloki","contributions": 4  },  {"login": "jkschneider","contributions": 4  },  {"login": "nmiyake","contributions": 4  },  {"login": "rfalke","contributions": 4  },  {"login": "SimY4","contributions": 3  },  {"login": "bstick12","contributions": 3  },  {"login": "mstrYoda","contributions": 3  },  {"login": "jacob-meacham","contributions": 3  },  {"login": "pnepywoda","contributions": 3  },  {"login": "santhosh-tekuri","contributions": 3  },  {"login": "jerzykrlk","contributions": 3  },  {"login": "Augustine-C","contributions": 2  },  {"login": "benmanbs","contributions": 2  },  {"login": "schlosna","contributions": 2  },  {"login": "dharmeshjogadia","contributions": 2  },  {"login": "edio","contributions": 2  },  {"login": "androidfred","contributions": 2  },  {"login": "stromnet","contributions": 2  }]

小结

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Reference

• https://blog.csdn.net/goldenfish1919/article/details/108592738