How to call third party API using spring rest template

3 min readDec 6, 2022

When we create an application, of course we need a third-party service or API such as the google API, facebook API, twitter API and others to support the application or business processes in the application. Spring boot already provides classes to integrate APIs from third parties, namely using rest templates. And this time we will try to integrate third party APIs using springboot rest template.

In this article we make simple Rest API and integration data USA population API.

Article Content:

Initiate the spring boot project
Add the required jar / dependencies to the spring boot project
Configuration for Spring
Create service
Create controller
Test

Technology

Java 11
Spring Boot
Maven

1.Initiate the spring boot project

To Create spring boot project, Open the Spring initializr https://start.spring.io.

2.Add the required jar / dependencies to the spring boot project

Add Dependencies for Spring Boot in pom.xml

<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.projectlombok</groupId>
			<artifactId>lombok</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

3.Configuration for Spring

Add Configuration in application.properties

server.name=springboot-rest-template
server.port=8081
url.usa.population = https://datausa.io/api/data?drilldowns=Nation&measures=Population

add rest template class into main application.

package id.co.lemoncode21.resttemplate;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
public class RestTemplateApplication {
public static void main(String[] args) {
 SpringApplication.run(RestTemplateApplication.class, args);
}
 @Bean
 public RestTemplate restTemplate(){
  return  new RestTemplate();
 }
}

4.Create service

service/GovernmentService.java

In this file we add two functions. one as an example to retrieve data by GET method and second as an example if our service needs to POST, UPDATE, DELETE methods to a third party service.

package id.co.lemoncode21.resttemplate.services;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

@Service
public class GovernmentService {
    @Autowired
    private RestTemplate restTemplate;
    @Value("${url.usa.population}")
    private String url;
    //   example get API
    public Object getAllData() {
        try {
            HttpHeaders headers = new HttpHeaders();
            headers.add(HttpHeaders.ACCEPT, "application/json");
            headers.add(HttpHeaders.CONTENT_TYPE, "application/json");
            HttpEntity entity = new HttpEntity(headers);
            ResponseEntity<Object> response = restTemplate.exchange(url, HttpMethod.GET, entity, new ParameterizedTypeReference<Object>() {});
            return response.getBody();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
    //   example POST DELETE UPDATE API
    public Object postAPI(Object request) {
        try {
            HttpHeaders headers = new HttpHeaders();
            headers.add(HttpHeaders.ACCEPT, "application/json");
            headers.add(HttpHeaders.CONTENT_TYPE, "application/json");
            // headers.add(HttpHeaders.AUTHORIZATION, token); add some token if API need Token
            HttpEntity entity = new HttpEntity(request, headers);
            // Change Object to object class according to response API
            // example
            // ResponseEntity<Person> response = restTemplate.exchange(url, HttpMethod.POST, entity, new ParameterizedTypeReference<Person>()});
            ResponseEntity<Object> response = restTemplate.exchange(url, HttpMethod.POST, entity, new ParameterizedTypeReference<Object>() {});
            return response.getBody();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}

5.Create controller

Controller is a REST Controller which has request mapping methods for RESTful requests.

controller/BaseController.java

package id.co.lemoncode21.resttemplate.controller;

import id.co.lemoncode21.resttemplate.services.GovernmentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class BaseController {
    @Autowired
    private GovernmentService governmentService;
    @GetMapping("/")
    public String Home() {
        return "Helo Home";
    }
    @GetMapping("/getAll")
    public Object getAll() {
        try {
            return this.governmentService.getAllData();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}