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VOOZH | about |
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VOOZH | about |
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.
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.
In this project, we are going to develop two Microservices
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
Please choose the following dependencies while creating the project.
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.
👁 Spring-Boot-Microservices-1-(2)
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.
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.
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.
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.
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.
Step 9: Create a Configuration Class
Go to the src > main > java > configuration and create a class EmployeeConfig and put the below code.
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
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"
}
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
Please choose the following dependencies while creating the project.
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.
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.
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.
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 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.
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: 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
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"
}
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.
Step 2: Modify EmployeeResponse Class
Also, go to the employee-service > src > main > java > response > EmployeeResponse and modify the EmployeeResponse class as below.
Please refer to the below image.
👁 microservice-communication-1
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.
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.
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.
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.
👁 microservice-communication-2
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.
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