Feign RequestInterceptor in Spring Boot

Upasana | July 14, 2020 | 2 min read | 6,269 views

In this tutorial we will learn how to use Feign RequestInterceptor by inject common headers to all outgoing requests in a Spring Boot 2.x application.

Gradle dependencies

First of all, we will add OpenFeign dependency to our gradle project.

build.gradle

dependencies {
    implementation "org.springframework.boot:spring-boot-starter-web"
    implementation "org.springframework.cloud:spring-cloud-starter-openfeign"
}

You can always head to https://start.spring.io/ for creating a Spring Boot starter project.

RequestInterceptor Bean

Feign provides RequestInterceptor interface that can be used for adding/removing/mutating any part of the request.

RequestInterceptor.java

public interface RequestInterceptor {

    /**
    * Called for every request. Add data using methods on the supplied RequestTemplate.
    */
    void apply(RequestTemplate template);
}

All we need to do is to create a Bean of type RequestInterceptor inside a config class and provide that configuration to FeignClient.

FeignConfig.class

import feign.RequestInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;

public class FeignConfig {  (1)

    @Bean
    public RequestInterceptor requestInterceptor() {
        return requestTemplate -> {
            requestTemplate.header("Content-Type", "application/json");
            requestTemplate.header("Accept", "application/json");
            requestTemplate.header("header_1", "value_1");
            requestTemplate.header("header_2", "value_2");
            requestTemplate.header("header_3", "value_3");
        };
    }
}

1	Do not annotate this class with `@Configuration` annotation, otherwise this configuration will become global i.e. all FeignClients will inherit this config in that case.

This will create a RequestInterceptor that will inject 5 headers to each request.

Now we will create a FeignClient applying the above configuration (FeignConfig):

Creating a Feign Client for stores-service

@FeignClient(value = "stores", configuration = {FeignConfig.class}) (1)
public interface StoreClient {

    @RequestMapping(method = RequestMethod.GET, value = "/stores")
    List<Store> getStores();
}

1	We have specified FeignConfig using configuration attribute of `FeignClient` annotation.

Now all the requests made by StoreClient will include the common headers to outgoing Http requests.

Alternate configuration using application.properties

Optionally, we can configure our feign client using application.yml by specifying the request interceptors.

application.yml

feign:
  client:
    config:
      stores:
        connectTimeout: 5000
        readTimeout: 5000
        loggerLevel: full
        requestInterceptors:
          - com.foo.FooRequestInterceptor   (1)

1	This should be replaced by fully qualified name of the RequestInterceptor

Running the application

Main application

@SpringBootApplication
@EnableFeignClients (1)
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}