昨天学springcloud，然后出了这么一个异常，
最后发现是只配置了Eureka的service的application.yml文件，但是我把Eureka的client的application文件给忘了。
最后如下：service
server:
port: 7001
eureka:
instance:
hostname: localhost
client:
register-with-eureka: false
fetch-registry: false
service-url:
defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
client
eureka:
client:
register-with-eureka: true
fetch-registry: true
service-url:
defaultZone: http://localhost:7001/eureka/