Spring Cloud - OpenFeign with Example Project

OpenFeign is an open-source project originally developed by Netflix and later moved to the open-source community. It is a declarative REST client that allows developers to write HTTP clients by simply creating Java interfaces. Spring Cloud integrates OpenFeign, making it very convenient to call REST APIs exposed by microservices or third-party applications.

With Feign, you don’t need to write boilerplate code for REST calls (like using RestTemplate or WebClient). Instead, Spring automatically generates the implementation at runtime.

Why Use OpenFeign

• Declarative style: Just define an interface and annotate methods with mappings (@GetMapping, @PostMapping, etc.).
• Less boilerplate code compared to RestTemplate.
• Integration with Spring Cloud: Works seamlessly with service discovery (Eureka), Ribbon (client-side load balancing) and resilience patterns.
• Readable and maintainable code.

Dependencies For OpenFeign

For Maven:

Add this dependency to the pom.xml file.

<dependency>

<groupId>org.springframework.cloud</groupId>

<artifactId>spring-cloud-starter-openfeign</artifactId>

</dependency>

For Gradle:

Add the following entries to the build.gradle file.

dependencies {

implementation 'org.springframework.cloud:spring-cloud-starter-openfeign'

}

How to Include Feign

After adding the library annotate the main Application file with this @EnableFeignClients annotation like below

@SpringBootApplication

@EnableFeignClients

public class Application {

public static void main(String[] args) {

SpringApplication.run(Application.class, args);

}

}

Create an Interface and annotate it with @FeignClient and declare your calling methods like below

@FeignClient(name = "giveYourServiceName", url = "provideYourUrlHere", path = "provideYourContextPathHere")

public interface AddressClient {

@GetMapping("/address/{id}")

public ResponseEntity<AddressResponse> getAddressByEmployeeId(@PathVariable("id") int id);

}

Let's understand the whole thing by developing two Spring Boot projects.

Example Project: Employee-Service and Address-Service

In this project, we are going to develop two Microservices

1. employee-service
2. address-service

1. Developing Employee-Service Step by Step

Step 1: Create a New Spring Boot Project

Create a Spring Boot Project for this project choose the following things

• Project: Maven
• Language: Java
• Packaging: Jar
• Java: 17

 Please choose the following dependencies while creating the project.

• Spring Boot DevTools
• Spring Data JPA
• MySQL Driver
• Spring Web
• OpenFeign

Generate the project and run it in IntelliJ IDEA by referring to the above article.

Note: We have used the MySQL database in this project.

Project Structure:

pom.xml:

Step 2: Database Setup

Go to your MySQL Workbench and create a schema named gfgmicroservicesdemo and inside that create a table called employee and put some sample data as shown in the below image. Here we have created 4 columns and put some sample data.

1. id
2. name
3. email
4. age

👁 Spring-Boot-Microservices-1

Step 3: application.properties

Now make the following changes in your application.properties file.

Step 4: Create Entity Class

Go to the src > main > java > entity and create a class Employee and put the below code. This is our model class.

Step 5: Create Your Repository Interface

Go to the src > main > java > repository and create an interface EmployeeRepo and put the below code. This is our repository where we write code for all the database-related stuff.

To Know more about JpaRepository -> JpaRepository.

Step 6: Create Response Classes

Go to the employee-service > src > main > java > response and create a class AddressResponse and put the below code.

AddressResponse.java

Go to the src > main > java > response and create a class EmployeeResponse and put the below code.

EmployeeResponse.java

Step 7: Feign Client

Go to the employee-service > src > main > java > feignclient and create an interface AddressClient and put the below code.

Step 8: Modify EmployeeServiceApplication Class

Go to the employee-service > src > main > java > EmployeeServiceApplication and annotate it with @EnableFeignClients annotation. Below is the complete code for EmployeeServiceApplication Class.

Step 9: Create Your Service Class

Now go to the employee-service > src > main > java > service > EmployeeService and modify the EmployeeService class as below. Add the below code inside this class.

Below is the complete code for EmployeeService Class.

Step 10: Create Controller

Go to the src > main > java > controller and create a class EmployeeController and put the below code. Here we are going to create an endpoint "/employees/{id}" to find an employee using id.

Step 11: Create a Configuration Class

Go to the src > main > java > configuration and create a class EmployeeConfig and put the below code.

Developing address-service Step by Step

Step 1: Create a New Spring Boot Project

Create a Spring Boot Project for this project choose the following things

• Project: Maven
• Language: Java
• Packaging: Jar
• Java: 17

 Please choose the following dependencies while creating the project.

• Spring Boot DevTools
• Spring Data JPA
• MySQL Driver
• Spring Web

Generate the project and run it in IntelliJ IDEA by referring to the above article.

Note: We have used the MySQL database in this project.

Step 2: Database Setup

Go to your MySQL Workbench and create a schema named gfgmicroservicesdemo and inside that create a table called address and put some sample data as shown in the below image. 

Address Table:

Here we have created 4 columns and put some sample data.

1. id
2. city
3. state
4. employee_id

Note: In the Address table, employee_id is a foreign key so create it accordingly. We are going to perform a SQL join operation in our native SQL query. So create tables carefully.

👁 Spring-Boot-Native-Query-1

Before moving to IntelliJ IDEA let's have a look at the complete project structure for our Microservices.

👁 Spring-Boot-Native-Query-2

pom.xml:

Step 3: application.properties

Now make the following changes in your application.properties file.

Step 4: Create Entity Class

Go to the src > main > java > entity and create a class Address and put the below code. This is our model class.

Step 5: Create Repository Interface

Go to the src > main > java > repository and create an interface AddressRepo and put the below code. This is our repository where we write code for all the database-related stuff.

Note: Please refer to this article to know more about JpaRepository.

Step 6: Create an AddressResponse Class

Go to the src > main > java > response and create a class AddressResponse and put the below code.

Step 7: Create Service Class

Go to the src > main > java > service and create a class AddressService and put the below code. This is our service class where we write our business logic.

Step 8: Create an Address Controller

Go to the src > main > java > controller and create a class AddressController and put the below code. Here we are going to create an endpoint "/address/{employeeId}" to find the address using employee_id. Thats why we have created a foreign key in the Address table and we have performed the SQL join operation in the native query to get our desired result.

Step 9: Create a Configuration Class

Go to the src > main > java > configuration and create a class AddressConfig and put the below code.

Note: To know more about Configuration and Bean Annotation->

• Spring @Configuration Annotation with Example
• Spring @Bean Annotation with Example

Run Both Your Address and Employee Microservices

Now run your both Address and Employee Microservices. If everything goes well then you may see the following screen in your console. Please refer to the below image.

• Start address-service on port 8081.
• Start employee-service on port 8080

👁 microservice-communication-2

Test Your Endpoint in Postman

Now open Postman and hit the following URL

GET: http://localhost:8080/employee-service/employees/2

And you can see the following response

{

"id": 2,

"name": "Asish",

"email": "asis@gmail",

"age": "30",

"addressResponse": {

"id": 1,

"city": "BLS",

"state": "Odisha"

}

}

Please refer to the below image.

👁 microservice-communication-3

With this setup, employee-service fetches employee details and calls address-service using Feign Client to get address details.

Related Articles

• Spring @Configuration Annotation with Example
• Spring @Bean Annotation with Example