Spring Cloud: Interview Questions UPDATING

The OpenFeign service-call process

flowchart TD

A["Business code calls
userClient.getById(1L)"] --> B["JDK dynamic proxy Proxy.invoke"]

B --> C["Feign InvocationHandler
MethodHandler"]

C --> D["Contract parses annotations
@GetMapping / @PathVariable"]

D --> E["RequestTemplate builds the HTTP request"]

E --> F["Parameter binding
Path / Query / Body / Header"]

F --> G["Service name resolution: user-service"]

G --> H["Service discovery: Nacos / Eureka"]

H --> I["LoadBalancer load balancing"]

I --> J["Select instance IP:PORT"]

J --> K["HTTP Client executor
OkHttp / Apache / JDK"]

K --> L["Send HTTP request GET /user/1"]

L --> M["Remote service: user-service"]

M --> N["Controller handles the request"]

N --> O["Return JSON"]

O --> P["Feign Decoder deserializes"]

P --> Q["JSON → UserDTO"]

Q --> R["Return to business code"]