Here’s a step-by-step guide on how to use this Spring Boot application:

Prerequisites

1. Java Development Kit (JDK): Ensure you have JDK 11 or later installed.
2. MySQL Database: Install MySQL and create a database. Also, add a table named employee to hold employee data.
3. Spring Boot Setup: Add the necessary dependencies to your build.gradle file if using Gradle.

Step 1: Configure Database

In MySQL, create a database and an employee table:

CREATE DATABASE your_database_name;

USE your_database_name;

CREATE TABLE employee (
    id BIGINT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    department VARCHAR(100)
);

Replace your_database_name with the name you want for your database.

Step 2: Configure Application Properties

In src/main/resources/application.properties, set your MySQL connection properties:

spring.datasource.url=jdbc:mysql://localhost:3306/your_database_name
spring.datasource.username=your_username
spring.datasource.password=your_password
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

Replace your_database_name, your_username, and your_password with your actual database credentials.

Step 3: Build and Run the Application

Navigate to your project directory and run the application using the Gradle command:

./gradlew bootRun

Alternatively, you can run the Demo1Application.java class directly from your IDE (e.g., IntelliJ, Eclipse) by clicking "Run."

Step 4: Test the API Endpoints

You can use a tool like Postman or curl to test the REST endpoints.

1. Get All Employees

   • Request: GET /api/employees
   • Example: Retrieve all employees.

   curl -X GET http://localhost:8080/api/employees

2. Add a New Employee

   • Request: POST /api/employees
   • Example: Add a new employee with name "John Doe" and department "Engineering".

   curl -X POST http://localhost:8080/api/employees -H "Content-Type: application/json" -d '{"name": "John Doe", "department": "Engineering"}'

3. Update an Employee

   • Request: PUT /api/employees
   • Example: Update an existing employee with id = 1.

   curl -X PUT http://localhost:8080/api/employees -H "Content-Type: application/json" -d '{"id": 1, "name": "Jane Doe", "department": "HR"}'

4. Delete an Employee

   • Request: DELETE /api/employees/{id}
   • Example: Delete an employee with id = 1.

   curl -X DELETE http://localhost:8080/api/employees/1

Summary of Endpoints

• GET /api/employees: Retrieve a list of all employees.
• POST /api/employees: Add a new employee.
• PUT /api/employees: Update an existing employee.
• DELETE /api/employees/{id}: Delete an employee by ID.

Additional Notes

• Error Handling: For a real application, you might add error handling to ensure better responses when something goes wrong.
• Testing: You can create tests in the DemoApplicationTests.java file to verify each component works as expected.