How to Create a REST API using Java Spring Boot?
Representational State Transfer (REST) is a software architectural style that defines a set of constraints for creating web services. RESTful web services allow systems to access and manipulate web resources through a uniform and predefined set of stateless operations. Unlike SOAP, which exposes its own set of operations, RESTful web services rely on simple HTTP methods such as GET, POST, PUT and DELETE.
Why Spring Boot?
Spring Boot makes it easy to create production-ready apps:
- Built on top of Spring Framework
- Reduces boilerplate code with auto-configurations
- Quick setup for REST APIs
- Beginner-friendly
Step-by-Step Implementation of REST API in Spring Boot
Step 1: Create the Spring Boot Project
Using Spring Initializr (Recommended)
1. Open Spring Initializr in your browser.
2. Fill in the project details:
- Project: Maven
- Language: Java
- Spring Boot version: (latest stable, e.g., 3.1.x)
- Group: com. example
- Artifact: demo
- Name: demo
- Packaging: Jar
- Java version: 17+
3. Click Add Dependencies-> Select Spring Web.
4. Click Generate-> It will download a .zip file.
5. Extract the zip-> Open it in your IDE (IntelliJ / Eclipse / VS Code).
Step 2: Define the Employee Entity
Create a simple Employee class inside com.example.demo:
package com.example.demo;
// Employee entity class
public class Employee {
private Integer id;
private String firstName;
private String lastName;
private String email;
// Default constructor
public Employee() {}
// Parameterized constructor
public Employee(Integer id, String firstName, String lastName, String email) {
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
this.email = email;
}
// Getters and Setters
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "Employee [id=" + id + ", firstName=" + firstName +
", lastName=" + lastName + ", email=" + email + "]";
}
}
Step 3: Create a Storage Class
Create a class to hold a list of employees.
package com.example.demo;
import java.util.ArrayList;
import java.util.List;
// Storage class for employees
public class Employees {
private List<Employee> employeeList;
// Get the employee list (initialize if null)
public List<Employee> getEmployeeList() {
if (employeeList == null) {
employeeList = new ArrayList<>();
}
return employeeList;
}
public void setEmployeeList(List<Employee> employeeList) {
this.employeeList = employeeList;
}
}
Step 4: Create the DAO Class
The DAO class will handle adding and retrieving employees.
package com.example.demo;
import org.springframework.stereotype.Repository;
@Repository
public class EmployeeDAO {
private static Employees employees = new Employees();
static {
// Initialize with sample employees
employees.getEmployeeList()
.add(new Employee(1, "Prem", "Tiwari", "prem@gmail.com"));
employees.getEmployeeList()
.add(new Employee(2, "Vikash", "Kumar", "vikash@gmail.com"));
employees.getEmployeeList()
.add(new Employee(3, "Ritesh", "Ojha", "ritesh@gmail.com"));
}
// Retrieve all employees
public Employees getAllEmployees() {
return employees;
}
// Add an employee
public void addEmployee(Employee employee) {
employees.getEmployeeList().add(employee);
}
}
Step 5: Create the Controller
The controller contains the REST API endpoints.
package com.example.demo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
import java.net.URI;
// REST Controller for managing employees
@RestController
@RequestMapping("/employees")
public class EmployeeController {
@Autowired
private EmployeeDAO employeeDao;
// GET endpoint to fetch all employees
@GetMapping("/")
public Employees getEmployees() {
return employeeDao.getAllEmployees();
}
// POST endpoint to add a new employee
@PostMapping("/")
public ResponseEntity<Object>
addEmployee(@RequestBody Employee employee) {
// Generate ID for the new employee
Integer id = employeeDao.getAllEmployees()
.getEmployeeList().size() + 1;
employee.setId(id);
// Add employee to the list
employeeDao.addEmployee(employee);
// Build location URI for the new employee
URI location = ServletUriComponentsBuilder
.fromCurrentRequest()
.path("/{id}")
.buildAndExpand(employee.getId())
.toUri();
return ResponseEntity.created(location).build();
}
}
Step 6: Run the Application
Open DemoApplication.java (already generated by Spring Boot) and run it:
package com.example.demo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
Step 7: Testing the API
Now we can test the API using tools like Postman or a web browser.
GET Request: Fetch all employees
URL: http://localhost:8080/employees/
Response:
POST Request: Add a new employee
Response:
Again hitting the GET request after performing the POST request:
This concludes creating a REST API using Spring Boot. Now we have a fully functioning API to manage employees.
