FeignClient also known as Spring Cloud OpenFeign is a Declarative REST Client in Spring Boot Web Application. But what do you mean by Declarative REST Client? It means we need to specify the client specification as an Interface and Spring Boot will take care of the implementation for us. Writing web services with the help of FeignClient is very easier. FeignClient is mostly used to consume REST API endpoints which are exposed by third-party or microservice.
How to Use FeignClient in Spring Boot Application?
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' }
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); }
Now it’s ready for use in the service class file. You can refer to the below code
@Service public class EmployeeService { // More Code Here // ------------- // Spring will create the implementation // for this class // and will inject the bean here (proxy) @Autowired private AddressClient addressClient; public EmployeeResponse getEmployeeById(int id) { // More Code Here // Using FeignClient ResponseEntity<AddressResponse> addressResponse = addressClient.getAddressByEmployeeId(id); employeeResponse.setAddressResponse(addressResponse.getBody()); return employeeResponse; } }
Let’s understand the whole thing by developing two microservices and let’s communicate with each other using FeignClient.
Example Project
In this project, we are going to develop two Microservices
- employee-service
- address-service
Developing employee-service Step by Step
Step 1: Create a New Spring Boot Project in Spring Initializr
To create a new Spring Boot project, please refer to How to Create a Spring Boot Project in Spring Initializr and Run it in IntelliJ IDEA. 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.
Step 2: Create Schema in MySQL Workbench and Put Some Sample Data
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.
- id
- name
- age
Now we are going to fetch Employee Data from Employee Table in our Spring Boot project. To do it refer to the following steps. Before moving to IntelliJ IDEA let’s look at the complete project structure for our Microservices.
Step 3: Make Changes in Your application.properties File
Now make the following changes in your application.properties file.
spring.datasource.url=jdbc:mysql://localhost:3306/gfgmicroservicesdemo spring.datasource.username=put your username here spring.datasource.password=put your password here spring.application.name=employee-service server.port=8080 # Set Your Context Path Here server.servlet.context-path=/employee-service
Step 4: Create Your Entity/Model Class
Go to the src > main > java > entity and create a class Employee and put the below code. This is our model class.
Java
package com.gfg.employeaap.entity; import jakarta.persistence.*; @Entity @Table (name = "employee" ) public class Employee { @Id @GeneratedValue (strategy = GenerationType.IDENTITY) @Column (name = "id" ) private int id; @Column (name = "name" ) private String name; @Column (name = "email" ) private String email; @Column (name = "age" ) private String age; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } public String getEmail() { return email; } public void setEmail(String email) { this .email = email; } public String getAge() { return age; } public void setAge(String age) { this .age = age; } } |
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.
Java
package com.gfg.employeaap.repository; import com.gfg.employeaap.entity.Employee; import org.springframework.data.jpa.repository.JpaRepository; @Repository public interface EmployeeRepo extends JpaRepository<Employee, Integer> { } |
Note: Please refer to this article to know more about JpaRepository.
Step 6: Create an EmployeeResponse Class
Go to the src > main > java > response and create a class EmployeeResponse and put the below code.
Java
package com.gfg.employeaap.response; public class EmployeeResponse { private int id; private String name; private String email; private String age; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } public String getEmail() { return email; } public void setEmail(String email) { this .email = email; } public String getAge() { return age; } public void setAge(String age) { this .age = age; } } |
Step 7: Create Your Service Class
Go to the src > main > java > service and create a class EmployeeService and put the below code. This is our service class where we write our business logic.
Java
package com.gfg.employeaap.service; import com.gfg.employeaap.entity.Employee; import com.gfg.employeaap.repository.EmployeeRepo; import com.gfg.employeaap.response.EmployeeResponse; import org.modelmapper.ModelMapper; import org.springframework.beans.factory.annotation.Autowired; import java.util.Optional; @Service public class EmployeeService { @Autowired private EmployeeRepo employeeRepo; @Autowired private ModelMapper mapper; public EmployeeResponse getEmployeeById( int id) { Optional<Employee> employee = employeeRepo.findById(id); EmployeeResponse employeeResponse = mapper.map(employee, EmployeeResponse. class ); return employeeResponse; } } |
Step 8: Create an Employee 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.
Java
package com.gfg.employeaap.controller; import com.gfg.employeaap.response.EmployeeResponse; import com.gfg.employeaap.service.EmployeeService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.HttpStatus; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RestController; @RestController public class EmployeeController { @Autowired private EmployeeService employeeService; @GetMapping ( "/employees/{id}" ) private ResponseEntity<EmployeeResponse> getEmployeeDetails( @PathVariable ( "id" ) int id) { EmployeeResponse employee = employeeService.getEmployeeById(id); return ResponseEntity.status(HttpStatus.OK).body(employee); } } |
Step 9: Create a Configuration Class
Go to the src > main > java > configuration and create a class EmployeeConfig and put the below code.
Java
package com.gfg.employeaap.configuration; import com.gfg.employeaap.service.EmployeeService; import org.modelmapper.ModelMapper; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class EmployeeConfig { @Bean public ModelMapper modelMapperBean() { return new ModelMapper(); } } |
Note: You may refer to these two articles
Before running the Microservice below is the complete pom.xml file. Please cross-verify if you have missed some dependencies
XML
<? xml version = "1.0" encoding = "UTF-8" ?> < project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd" > < modelVersion >4.0.0</ modelVersion > < parent > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-parent</ artifactId > < version >3.0.2</ version > < relativePath /> <!-- lookup parent from repository --> </ parent > < groupId >com.gfg.employeaap</ groupId > < artifactId >employee-service</ artifactId > < version >0.0.1-SNAPSHOT</ version > < name >employee-service</ name > < description >Employee Service</ description > < properties > < java.version >17</ java.version > < spring-cloud.version >2022.0.2</ spring-cloud.version > </ properties > < dependencies > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-data-jpa</ artifactId > </ dependency > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-web</ artifactId > </ dependency > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-devtools</ artifactId > < scope >runtime</ scope > < optional >true</ optional > </ dependency > < dependency > < groupId >com.mysql</ groupId > < artifactId >mysql-connector-j</ artifactId > < scope >runtime</ scope > </ dependency > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-test</ artifactId > < scope >test</ scope > </ dependency > < dependency > < groupId >org.modelmapper</ groupId > < artifactId >modelmapper</ artifactId > < version >3.1.1</ version > </ dependency > < dependency > < groupId >org.springframework.cloud</ groupId > < artifactId >spring-cloud-starter-openfeign</ artifactId > </ dependency > </ dependencies > < dependencyManagement > < dependencies > < dependency > < groupId >org.springframework.cloud</ groupId > < artifactId >spring-cloud-dependencies</ artifactId > < version >${spring-cloud.version}</ version > < type >pom</ type > < scope >import</ scope > </ dependency > </ dependencies > </ dependencyManagement > < build > < plugins > < plugin > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-maven-plugin</ artifactId > </ plugin > </ plugins > </ build > </ project > |
Step 10: Run Your Employee Microservice
To run your Employee Microservice src > main > java > EmployeeServiceApplication and click on the Run button. If everything goes well then you may see the following screen in your console. Please refer to the below image.
Step 11: Test Your Endpoint in Postman
Now open Postman and hit the following URL
GET: http://localhost:8080/employee-service/employees/1
And you can see the following response
{ "id": 1, "name": "Amiya", "email": "ar@gmail", "age": "25" }
Developing address-service Step by Step
Step 1: Create a New Spring Boot Project in Spring Initializr
To create a new Spring Boot project, please refer to How to Create a Spring Boot Project in Spring Initializr and Run it in IntelliJ IDEA. 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: Create Schema in MySQL Workbench and Put Some Sample Data
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.
- id
- city
- state
- 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.
Before moving to IntelliJ IDEA let’s have a look at the complete project structure for our Microservices.
Step 3: Make Changes in Your application.properties File
Now make the following changes in your application.properties file.
spring.datasource.url=jdbc:mysql://localhost:3306/gfgmicroservicesdemo spring.datasource.username=put your username here spring.datasource.password=put your password here spring.application.name=address-service server.port=8081 server.servlet.context-path=/address-service
Step 4: Create Your Entity/Model Class
Go to the src > main > java > entity and create a class Address and put the below code. This is our model class.
Java
package com.gfg.addressapp.entity; import jakarta.persistence.*; @Entity @Table (name = "address" ) public class Address { @Id @GeneratedValue (strategy = GenerationType.IDENTITY) @Column (name = "id" ) private int id; @Column (name = "city" ) private String city; @Column (name = "state" ) private String state; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getCity() { return city; } public void setCity(String city) { this .city = city; } public String getState() { return state; } public void setState(String state) { this .state = state; } } |
Step 5: Create Your 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.
Java
package com.gfg.addressapp.repository; import com.gfg.addressapp.entity.Address; import java.util.Optional; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.Query; import org.springframework.data.repository.query.Param; @Repository public interface AddressRepo extends JpaRepository<Address, Integer> { @Query ( nativeQuery = true , value = "SELECT ea.id, ea.city, ea.state FROM gfgmicroservicesdemo.address ea join gfgmicroservicesdemo.employee e on e.id = ea.employee_id where ea.employee_id=:employeeId" ) Optional<Address> findAddressByEmployeeId( @Param ( "employeeId" ) int employeeId); } |
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.
Java
package com.gfg.addressapp.response; public class AddressResponse { private int id; private String city; private String state; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getCity() { return city; } public void setCity(String city) { this .city = city; } public String getState() { return state; } public void setState(String state) { this .state = state; } } |
Step 7: Create Your 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.
Java
package com.gfg.addressapp.service; import com.gfg.addressapp.entity.Address; import com.gfg.addressapp.repository.AddressRepo; import com.gfg.addressapp.response.AddressResponse; import org.modelmapper.ModelMapper; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import java.util.Optional; @Service public class AddressService { @Autowired private AddressRepo addressRepo; @Autowired private ModelMapper mapper; public AddressResponse findAddressByEmployeeId( int employeeId) { Optional<Address> addressByEmployeeId = addressRepo.findAddressByEmployeeId(employeeId); AddressResponse addressResponse = mapper.map(addressByEmployeeId, AddressResponse. class ); return addressResponse; } } |
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.
Java
package com.gfg.addressapp.controller; import com.gfg.addressapp.response.AddressResponse; import com.gfg.addressapp.service.AddressService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.HttpStatus; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RestController; @RestController public class AddressController { @Autowired private AddressService addressService; @GetMapping ( "/address/{employeeId}" ) public ResponseEntity<AddressResponse> getAddressByEmployeeId( @PathVariable ( "employeeId" ) int employeeId) { AddressResponse addressResponse = addressService.findAddressByEmployeeId(employeeId); return ResponseEntity.status(HttpStatus.OK).body(addressResponse); } } |
Step 9: Create a Configuration Class
Go to the src > main > java > configuration and create a class AddressConfig and put the below code.
Java
package com.gfg.addressapp.configuration; import com.gfg.addressapp.service.AddressService; import org.modelmapper.ModelMapper; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class AddressConfig { @Bean public ModelMapper modelMapperBean() { return new ModelMapper(); } } |
Note: You may refer to these two articles
Before running the Microservice below is the complete pom.xml file. Please cross-verify if you have missed some dependencies
XML
<? xml version = "1.0" encoding = "UTF-8" ?> < project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd" > < modelVersion >4.0.0</ modelVersion > < parent > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-parent</ artifactId > < version >3.0.2</ version > < relativePath /> <!-- lookup parent from repository --> </ parent > < groupId >com.gfg.addressapp</ groupId > < artifactId >address-service</ artifactId > < version >0.0.1-SNAPSHOT</ version > < name >address-service</ name > < description >Address Service</ description > < properties > < java.version >17</ java.version > </ properties > < dependencies > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-data-jpa</ artifactId > </ dependency > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-web</ artifactId > </ dependency > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-devtools</ artifactId > < scope >runtime</ scope > < optional >true</ optional > </ dependency > < dependency > < groupId >com.mysql</ groupId > < artifactId >mysql-connector-j</ artifactId > < scope >runtime</ scope > </ dependency > < dependency > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-test</ artifactId > < scope >test</ scope > </ dependency > < dependency > < groupId >org.modelmapper</ groupId > < artifactId >modelmapper</ artifactId > < version >3.1.1</ version > </ dependency > </ dependencies > < build > < plugins > < plugin > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-maven-plugin</ artifactId > </ plugin > </ plugins > </ build > </ project > |
Step 10: Run Your Address Microservice
To run your Address Microservice src > main > java > AddressServiceApplication and click on the Run button. If everything goes well then you may see the following screen in your console. Please refer to the below image.
Step 11: Test Your Endpoint in Postman
Now open Postman and hit the following URL
GET: http://localhost:8081/address-service/address/2
And you can see the following response
{ "id": 1, "city": "BLS", "state": "Odisha" }
Microservices Communication using FeignClient
Now let’s communicate between two microservices using FeignClient. So we are going to get the address data by the employeeId of an employee and when we communicate we are going to get a response like the below. So let’s implement it.
{ "id": 2, "name": "Asish", "email": "asis@gmail", "age": "30", "addressResponse": { "id": 1, "city": "BLS", "state": "Odisha" } }
Here employee-service is going to consume data from the address-service. So let’s write the logic in the employee-service.
Step 1: Create an AddressResponse Class
Go to the employee-service > src > main > java > response and create a class AddressResponse and put the below code.
Java
package com.gfg.employeaap.response; public class AddressResponse { private int id; private String city; private String state; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getCity() { return city; } public void setCity(String city) { this .city = city; } public String getState() { return state; } public void setState(String state) { this .state = state; } } |
Step 2: Modify EmployeeResponse Class
Also, go to the employee-service > src > main > java > response > EmployeeResponse and modify the EmployeeResponse class as below.
Java
package com.gfg.employeaap.response; public class EmployeeResponse { private int id; private String name; private String email; private String age; // Add AddressResponse Here private AddressResponse addressResponse; public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } public String getEmail() { return email; } public void setEmail(String email) { this .email = email; } public String getAge() { return age; } public void setAge(String age) { this .age = age; } public AddressResponse getAddressResponse() { return addressResponse; } public void setAddressResponse(AddressResponse addressResponse) { this .addressResponse = addressResponse; } } |
Please refer to the below image.
Step 3: Create an AddressClient Interface
Go to the employee-service > src > main > java > feignclient and create an interface AddressClient and put the below code.
Java
package com.gfg.employeaap.feignclient; import com.gfg.employeaap.response.AddressResponse; import org.springframework.cloud.openfeign.FeignClient; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; public interface AddressClient { @GetMapping ( "/address/{id}" ) public ResponseEntity<AddressResponse> getAddressByEmployeeId( @PathVariable ( "id" ) int id); } |
Step 4: 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.
Java
package com.gfg.employeaap; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.openfeign.EnableFeignClients; @SpringBootApplication @EnableFeignClients public class EmployeeServiceApplication { public static void main(String[] args) { SpringApplication.run(EmployeeServiceApplication. class , args); } } |
Step 5: Modify EmployeeService 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.
@Autowired private AddressClient addressClient; // Using FeignClient ResponseEntity<AddressResponse> addressResponse = addressClient.getAddressByEmployeeId(id); employeeResponse.setAddressResponse(addressResponse.getBody());
Below is the complete code for EmployeeService Class.
Java
package com.gfg.employeaap.service; import com.gfg.employeaap.entity.Employee; import com.gfg.employeaap.feignclient.AddressClient; import com.gfg.employeaap.repository.EmployeeRepo; import com.gfg.employeaap.response.AddressResponse; import com.gfg.employeaap.response.EmployeeResponse; import org.modelmapper.ModelMapper; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.ResponseEntity; import org.springframework.stereotype.Service; import java.util.Optional; @Service public class EmployeeService { @Autowired private EmployeeRepo employeeRepo; @Autowired private ModelMapper mapper; // Spring will create the implementation // for this class // and will inject the bean here (proxy) @Autowired private AddressClient addressClient; public EmployeeResponse getEmployeeById( int id) { Optional<Employee> employee = employeeRepo.findById(id); EmployeeResponse employeeResponse = mapper.map(employee, EmployeeResponse. class ); // Using FeignClient ResponseEntity<AddressResponse> addressResponse = addressClient.getAddressByEmployeeId(id); employeeResponse.setAddressResponse(addressResponse.getBody()); return employeeResponse; } } |
Step 6: 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.
Step 7: 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.