1. Feign API

package com.sande.configserver.api;


import java.util.concurrent.CompletableFuture;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;

import com.netflix.hystrix.HystrixCommand;

import feign.hystrix.HystrixFeign;
import io.netty.util.concurrent.Future;



@FeignClient(value = "user-server", fallback = UserApiFeignHystrix.class)
public interface UserApi {
	
	@PostMapping(value="/user/getByTokenUser")
	//CompletableFuture<User> getByTokenUser(@RequestParam("token") String token);
	HystrixCommand<User> getByTokenUser(@RequestParam("token") String token);
}

2. 实现服务降级的类

package com.sande.configserver.api;

import static org.hamcrest.CoreMatchers.nullValue;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import org.springframework.stereotype.Component;

import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommandGroupKey;
import com.netflix.hystrix.HystrixCommand.Setter;
import com.netflix.hystrix.contrib.javanica.utils.FutureDecorator;

import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.GenericFutureListener;
import net.bytebuddy.asm.Advice.Return;

@Component
public class UserApiFeignHystrix implements UserApi {
	private static final Setter hystrixCommandGroupKey = 
			Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("UserApi"));


	@Override
	public HystrixCommand<User> getByTokenUser(final String token) {

		return new HystrixCommand<User>(hystrixCommandGroupKey) {
			@Override
			protected User run() throws Exception {
				// TODO Auto-generated method stub
				System.out.println("Feign 服务异步调用服务降级");
				User user = new User();
				user.setPhone("13811111111");
				user.setUserName("lixia");
				return user;
			}
		};
	}
 
}

3. 服务调用方（消费端）的 Controller

package com.sande.configserver.api;

import static org.assertj.core.api.Assertions.setLenientDateParsing;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import feign.hystrix.HystrixFeign;


@RestController
public class UserController {
	@Resource UserApi userApi;
	
	@RequestMapping(value="/getByTokenUser")
	public User getByTokenUser(HttpServletRequest request,HttpServletResponse response) throws InterruptedException, ExecutionException {
		String token ="token_cef257c4db1d456fbea00f1e8a50b3b0";
		Future<User> future = userApi.getByTokenUser(token).queue();
		return future.get();
		
		
		
	}
}