Spring RestTemplate Spring REST Client GET, POST, PUT and DELETE Example

In this article, we will discuss how to use the Spring RestTemplate class to call Rest web services.

From the documentation, RestTemplate is the synchronous client to perform HTTP requests, exposing a simple, template method API over underlying HTTP client libraries such as the JDK HttpURLConnection, Apache HttpComponents, and others.

What we will build

We are building an application that uses Spring’s RestTemplate class to consume CRUD Rest web services. Basically, we will develop Rest client to consume CRUD RESTFul APIs for a Simple Employee Management System using Spring Boot 2 JPA and MySQL. Following are five REST APIs (Controller handler methods) are created for Employee resource.

diagram here

package net.guides.springboot2.springboot2jpacrudexample;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;

import net.guides.springboot2.springboot2jpacrudexample.model.Employee;

public class SpringRestClient {

    private static final String GET_EMPLOYEES_ENDPOINT_URL = "http://localhost:8080/api/v1/employees";
    private static final String GET_EMPLOYEE_ENDPOINT_URL = "http://localhost:8080/api/v1/employees/{id}";
    private static final String CREATE_EMPLOYEE_ENDPOINT_URL = "http://localhost:8080/api/v1/employees";
    private static final String UPDATE_EMPLOYEE_ENDPOINT_URL = "http://localhost:8080/api/v1/employees/{id}";
    private static final String DELETE_EMPLOYEE_ENDPOINT_URL = "http://localhost:8080/api/v1/employees/{id}";
    private static RestTemplate restTemplate = new RestTemplate();

    public static void main(String[] args) {
        SpringRestClient springRestClient = new SpringRestClient();

        // Step1: first create a new employee
        springRestClient.createEmployee();

        // Step 2: get new created employee from step1
        springRestClient.getEmployeeById();

        // Step3: get all employees
        springRestClient.getEmployees();

        // Step4: Update employee with id = 1
        springRestClient.updateEmployee();

        // Step5: Delete employee with id = 1
        springRestClient.deleteEmployee();
    }

    private void getEmployees() {

        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
        HttpEntity < String > entity = new HttpEntity < String > ("parameters", headers);

        ResponseEntity < String > result = restTemplate.exchange(GET_EMPLOYEES_ENDPOINT_URL, HttpMethod.GET, entity,
            String.class);

        System.out.println(result);
    }

    private void getEmployeeById() {

        Map < String, String > params = new HashMap < String, String > ();
        params.put("id", "1");

        RestTemplate restTemplate = new RestTemplate();
        Employee result = restTemplate.getForObject(GET_EMPLOYEE_ENDPOINT_URL, Employee.class, params);

        System.out.println(result);
    }

    private void createEmployee() {

        Employee newEmployee = new Employee("admin", "admin", "[email protected]");

        RestTemplate restTemplate = new RestTemplate();
        Employee result = restTemplate.postForObject(CREATE_EMPLOYEE_ENDPOINT_URL, newEmployee, Employee.class);

        System.out.println(result);
    }

    private void updateEmployee() {
        Map < String, String > params = new HashMap < String, String > ();
        params.put("id", "1");
        Employee updatedEmployee = new Employee("admin123", "admin123", "[email protected]");
        RestTemplate restTemplate = new RestTemplate();
        restTemplate.put(UPDATE_EMPLOYEE_ENDPOINT_URL, updatedEmployee, params);
    }

    private void deleteEmployee() {
        Map < String, String > params = new HashMap < String, String > ();
        params.put("id", "1");
        RestTemplate restTemplate = new RestTemplate();
        restTemplate.delete(DELETE_EMPLOYEE_ENDPOINT_URL, params);
    }
}