Use @FeignClient annotation in SpringBoot

@FeignClientis an annotation provided by Spring Cloud to declare a REST client based on Feign implementation.

Feign is a declarative HTTP client that simplifies the process of writing HTTP clients, describing HTTP APIs by defining interfaces and annotations without writing implementation code.

Some main parameters and detailed explanations of @FeignClient annotation

value/name: Used to specify the name of the target service.

AvailablevalueornameTo specify the name of the service, this name will be registered in the Service Discovery Center (such as Eureka) and used for service discovery.
Example:

@FeignClient(name = "example-service")

url: Used to specify the URL address of the target service.

If you know the exact address of the target service, you can useurlParameters are specified.
Example:

@FeignClient(url = "")

path: Optional, used to specify the base path requested by the client.

If the target service's API has a public base path, you can usepathSpecify the parameters so that the portion of the public path can be omitted when defining the request method.
Example:

@FeignClient(name = "example-service", path = "/api")

configuration: Optional, to specify the configuration class for Feign client.

You can specify a configuration class through this parameter to customize the Feign client.
Example:

@FeignClient(name = "example-service", configuration = )

fallback/fallbackFactory: Optional, used to specify the fallback processing logic when the Feign client request fails.

fallbackThe parameters can directly specify the class for the fallback process, andfallbackFactoryIt is a factory class that creates an instance of the fallback processing class.
Example:

@FeignClient(name = "example-service", fallback = )

contextId: Optional, to specify the context ID of the Feign client.

There may be multiple Feign clients in one application, throughcontextIdYou can specify a unique context ID for each client.
Example:

@FeignClient(name = "example-service", contextId = "myFeignClient")

By using@FeignClientAnnotation, you can easily declare a REST client and define an interface to communicate with the target service. Feign will automatically generate corresponding HTTP requests based on these definitions.

Give an example

Suppose you have a microservice architecture, with a service nameduser-service, it provides some user-related APIs, such as obtaining user information, creating users, etc.

Now you want to call it in another serviceuser-serviceAPI.

You can use Feign to achieve this.

First, you need to declare a Feign client interface in the caller's service:

import ;
import ;
import ;

@FeignClient(name = "user-service")
public interface UserServiceClient {

    @GetMapping("/users/{userId}")
    User getUserById(@PathVariable("userId") Long userId);
}

The above code defines a name calledUserServiceClientThe interface through@FeignClientThe annotation specifies the name of the target service asuser-service。

A method is declared in the interfacegetUserById, used to calluser-serviceIn-house/users/{userId}API, obtain user information based on user ID.

You can then inject it into the caller's serviceUserServiceClientAnd call the corresponding method:

import ;
import ;
import ;
import ;

@RestController
public class UserController {

    private final UserServiceClient userServiceClient;

    @Autowired
    public UserController(UserServiceClient userServiceClient) {
         = userServiceClient;
    }

    @GetMapping("/users/{userId}")
    public User getUser(@PathVariable("userId") Long userId) {
        return (userId);
    }
}

In this example,UserControlleris a Spring MVC controller, by injectionUserServiceClientCome to calluser-serviceAPI.

When called/users/{userId}When interfaced, an HTTP request will actually be sent to the Feign client proxyuser-serviceand return the corresponding result.

In this way, you can easily implement communication between services in the microservice architecture, and Feign simplifies the caller's code, making the whole process more concise and easy to maintain.

Summarize

The above is personal experience. I hope you can give you a reference and I hope you can support me more.