<dependency>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-starter-hystrix</artifactId>
</dependency>
<dependency>
   <groupId>com.netflix.hystrix</groupId>
   <artifactId>hystrix-javanica</artifactId>
   <version>RELEASE</version>
</dependency>

@EnableCircuitBreaker
或者@SpringCloudApplication
这个注解包含@SpringBootApplication

在Controller要降级的方法上加上
@HystrixCommand(fallbackMethod = "fallback")



后面跟的是方法

private String fallback(){
    return  "太拥挤了,请稍后再试。";
}


或者在Controller加上
@DefaultProperties(defaultFallback = "fallback")

@HystrixCommand(commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "3000")
    })