@FeignClient path属性路径前缀带路径变量时报错处理

现象

FeignClient注解中使用path属性定义url前缀时，如果使用了路径变量，则会报错
例如

@FeignClient(name = "user-api",
path = "/api/user/{id}")

报错

ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalArgumentException: Target is not a valid URI.] with root cause
java.net.URISyntaxException: Illegal character in path at index 25: http://user-api/api/user/{id}

源码分析

• feign.Target
  注：url成员值为@FeignClient配置的path属性值

public interface Target<T> {
	@Override
    public Request apply(RequestTemplate input) {
      if (input.url().indexOf("http") != 0) {
        input.target(url());
      }
      return input.request();
    }
}

• feign.RequestTemplate
  注：此处将path属性值直接解析为URI对象，如果包含形如{PathVariable}的路径变量，会导致解析异常

public final class RequestTemplate implements Serializable {
  public RequestTemplate target(String target) {
    /* target can be empty */
    if (Util.isBlank(target)) {
      return this;
    }

    /* verify that the target contains the scheme, host and port */
    if (!UriUtils.isAbsolute(target)) {
      throw new IllegalArgumentException("target values must be absolute.");
    }
    if (target.endsWith("/")) {
      target = target.substring(0, target.length() - 1);
    }
    try {
      /* parse the target */ 
      // 此处直接将path
      URI targetUri = URI.create(target);

      if (Util.isNotBlank(targetUri.getRawQuery())) {
        /*
         * target has a query string, we need to make sure that they are recorded as queries
         */
        this.extractQueryTemplates(targetUri.getRawQuery(), true);
      }

      /* strip the query string */
      this.target = targetUri.getScheme() + "://" + targetUri.getAuthority() + targetUri.getPath();
      if (targetUri.getFragment() != null) {
        this.fragment = "#" + targetUri.getFragment();
      }
    } catch (IllegalArgumentException iae) {
      /* the uri provided is not a valid one, we can't continue */
      throw new IllegalArgumentException("Target is not a valid URI.", iae);
    }
    return this;
  }
}

解决办法

如需使用路径变量使用@RequestMapping代替Path

@FeignClient(name = "user-api")
@RequestMapping("/api/user/{id}")