一、FeignClient注解

FeignClient注解被@Target(ElementType.TYPE)修飾，表示FeignClient注解的作用目標在接口上

@FeignClient(name = "github-client", url = "https://api.github.com", configuration = GitHubExampleConfig.class)public interface GitHubClient {  @RequestMapping(value = "/search/repositories", method = RequestMethod.GET)  String searchRepo(@RequestParam("q") String queryStr);}

聲明接口之后，在代碼中通過@Resource注入之后即可使用。@FeignClient標簽的常用屬性如下：

@FeignClient(name = "github-client",    url = "https://api.github.com",    configuration = GitHubExampleConfig.class,    fallback = GitHubClient.DefaultFallback.class)public interface GitHubClient {  @RequestMapping(value = "/search/repositories", method = RequestMethod.GET)  String searchRepo(@RequestParam("q") String queryStr);   /**   * 容錯處理類，當調用失敗時，簡單返回空字符串   */  @Component  public class DefaultFallback implements GitHubClient {    @Override    public String searchRepo(@RequestParam("q") String queryStr) {      return "";    }  }}

在使用fallback屬性時，需要使用@Component注解，保證fallback類被Spring容器掃描到,GitHubExampleConfig內容如下：

@Configurationpublic class GitHubExampleConfig {  @Bean  Logger.Level feignLoggerLevel() {    return Logger.Level.FULL;  }}

在使用FeignClient時，Spring會按name創建不同的ApplicationContext，通過不同的Context來隔離FeignClient的配置信息，在使用配置類時，不能把配置類放到Spring App Component scan的路徑下，否則，配置類會對所有FeignClient生效.

二、Feign Client 和@RequestMapping

當前工程中有和Feign Client中一樣的Endpoint時，Feign Client的類上不能用@RequestMapping注解否則，當前工程該endpoint http請求且使用accpet時會報404
Controller：

@RestController@RequestMapping("/v1/card")public class IndexApi {   @PostMapping("balance")  @ResponseBody  public Info index() {    Info.Builder builder = new Info.Builder();    builder.withDetail("x", 2);    builder.withDetail("y", 2);    return builder.build();  }}

Feign Client

@FeignClient(    name = "card",    url = "http://localhost:7913",    fallback = CardFeignClientFallback.class,    configuration = FeignClientConfiguration.class)@RequestMapping(value = "/v1/card")public interface CardFeignClient {   @RequestMapping(value = "/balance", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE)  Info info(); }