Alibaba cloud microservices (I) service registry Nacos, rest template and feign client

First, let's introduce the concept of service registration
Actually DNS It is a service registration , In microservices . The application instance obtains the information of the service instance through the registry , Use this information to request the parameters they provide

There are ten instances of a service ,client How to know which one to visit ？
Service registration is needed to help us
First deploy a service center locally Nacos:
Start good nacos On the one hand, it can monitor API, On the one hand, there is a console
First, deploy a service End

You can see nacos You can find that the service has been registered to the service center


Now deploy Consumer

consumer It can be used REST Template and Feign Client To write
Briefly introduce these two gadgets , They are all based on http Protocol to communicate

rest template It needs to be assembled every time url, It is relatively simple to use ,RestTemplate In splicing url When , You can specify ip Address + Port number , You can directly request the interface without going through the service registry ; You can also specify a service name , Request to go to the service registry first （ Such as nacos） Get the corresponding service ip Address + Port number , And then pass by HTTP Forward the request to the corresponding service interface （ need @LoadBalanced）

Feign The underlying implementation of is dynamic agent , Its use is realized through annotations , It is also mapped through the service center

About feigin Use ：
1. stay consumer add to @@EnableFeignClients
2. stay consumer add to Feign The interface of （ Use @FeignClient(value = “service-provider”), among value It refers to the services of producers ）,producer Is the service that implements this interface
3. stay producer Created in controller Interface , Realization 2 The specific logic of the interface in
4. stay consumer Call in the