18.3. RESTful API with Spring Boot

Spring Boot simplifies the development of production-ready Spring applications. It comes with embedded servers, auto-configuration, and starter dependencies.

Spring Boot is a powerful framework that makes it easier and quicker to develop applications in Spring by providing many features out of the box. These include embedded servers, which allow you to run your application without needing to install a separate server, and auto-configuration that sets up necessary components automatically. Starter dependencies simplify the inclusion of libraries and modules you need for a Spring application.

Think of Spring Boot like a ready-made meal kit. It provides you with everything you need to cook a delicious dinner without having to shop for individual ingredients. You just follow the simple steps to prepare your meal!

Step 1: Add Dependencies (pom.xml)

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

Step 2: Create Entity Class

public class Employee {
 private int id;
 private String name;
 private String department;
 // Getters and setters
}

Step 3: Create a Controller Class

@RestController
@RequestMapping("/api/employees")
public class EmployeeController {
 private List<Employee> employeeList = new ArrayList<>();
 @GetMapping
 public List<Employee> getAllEmployees() {
 return employeeList;
 }
 @PostMapping
 public Employee addEmployee(@RequestBody Employee employee) {
 employeeList.add(employee);
 return employee;
 }
 @PutMapping("/{id}")
 public Employee updateEmployee(@PathVariable int id, @RequestBody Employee updatedEmployee) {
 for (Employee emp : employeeList) {
 if (emp.getId() == id) {
 emp.setName(updatedEmployee.getName());
 emp.setDepartment(updatedEmployee.getDepartment());
 return emp;
 }
 }
 return null;
 }
 @DeleteMapping("/{id}")
 public String deleteEmployee(@PathVariable int id) {
 employeeList.removeIf(emp -> emp.getId() == id);
 return "Employee deleted successfully.";
 }
}

Creating a REST Controller in Spring Boot involves several steps:

1. Adding Dependencies: You need to include the spring-boot-starter-web dependency in your project's pom.xml file. This brings in all the necessary libraries to build a web application.
2. Creating Entity Class: An entity class represents the data model. Here, the Employee class is created, which has id, name, and department fields, along with their getters and setters.
3. Creating a Controller Class: The EmployeeController class is annotated with @RestController, which makes it handle HTTP requests. The @RequestMapping annotation specifies the base URL for all endpoints. Inside this class, methods handle HTTP GET, POST, PUT, and DELETE requests to interact with employee data.

Imagine you're building a library management system. The dependencies you add are like the tools you need to build shelves. The Employee class is like a blueprint for each librarian, detailing their job title, name, and department. The EmployeeController is like the librarian's system for checking books in and out; it defines how to add, update, and remove librarians in the database.

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