Spring Cloud Tutorial- REST Client using Netflix Feign Simple Example

We first add the netflix feign dependency in the pom as follows-

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>com.javainuse</groupId>
	<artifactId>employee-consumer</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.4.1.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-eureka</artifactId>
		</dependency>
		
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-ribbon</artifactId>
		</dependency>
		
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-feign</artifactId>
		</dependency>


	</dependencies>

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Camden.SR6</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>


</project>

We next define a Feign Client by creating an interface with @FeignClient annotation. We also specify the name value as "employee-producer". This value is the name of the service registered using Eureka for discovery. We define the method call to be made to consume the REST service exposed by the employee-producer module.

package com.javainuse.services;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.javainuse.controllers.Employee;

@FeignClient(name="employee-producer")
public interface RemoteCallService {
	@RequestMapping(method=RequestMethod.GET, value="/employee")
	public Employee getData();

}

Next we autowire the RemoteCallService in the ConsumerControllerClient class. Then using it make the REST call. Load Balancing is automatically taken care by Feign Client.

package com.javainuse.controllers;

import java.io.IOException;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.client.RestClientException;

import com.javainuse.services.RemoteCallService;

@Controller
public class ConsumerControllerClient {

	@Autowired
	private RemoteCallService loadBalancer;

	public void getEmployee() throws RestClientException, IOException {

		try {
			Employee emp = loadBalancer.getData();
			System.out.println(emp.getEmpId());
		} catch (Exception ex) {
			System.out.println(ex);
		}
	}

}

Finally we annotate the Spring Boot Main class with @EnableFeignClients.

package com.javainuse;

import java.io.IOException;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestClientException;

import com.javainuse.controllers.ConsumerControllerClient;

@SpringBootApplication
@EnableFeignClients
public class SpringBootHelloWorldApplication {

	public static void main(String[] args) throws RestClientException, IOException {
		ApplicationContext ctx = SpringApplication.run(SpringBootHelloWorldApplication.class, args);

		ConsumerControllerClient consumerControllerClient = ctx.getBean(ConsumerControllerClient.class);
		System.out.println(consumerControllerClient);
		consumerControllerClient.getEmployee();

	}

	@Bean
	public ConsumerControllerClient consumerControllerClient() {
		return new ConsumerControllerClient();
	}
}

As we had done in previous posts- Start the following Spring Boot Applications-

eureka-server
employee-producer
employee-consumer

On running the employee-consumer we get the output as follows-
cloud-8_3

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Spring Cloud- REST call using Netflix Feign Client

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Spring Cloud- REST call using Netflix Feign Client

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