package com.javatest.demo;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
@Entity
@Table(name="users")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String age;
private String city;
private int quota;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public int getQuota() {
return quota;
}
public void setQuota(int quota) {
this.quota = quota;
}
// getters and setters
}
UserController.java
package com.javatest.demo;
import java.util.List;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.data.jpa.repository.JpaRepository;
interface UserRepository extends JpaRepository<User, Long> {
// Custom queries can be defined here
}
@RestController
@RequestMapping("users")
public class UserController {
private final UserRepository userRepository;
public UserController(UserRepository userRepository) {
this.userRepository = userRepository;
}
@RequestMapping("")
public String index() {
return "I am from index";
}
@RequestMapping("listing")
public List<User> listing() {
// List<User> users = new ArrayList<>();
return userRepository.findAll();
}
@DeleteMapping("delete/{id}")
public String deleteUser(@PathVariable Long id) {
// Check if the user with the specified ID exists
if (userRepository.existsById(id)) {
userRepository.deleteById(id);
return String.format("User %s is deleted successfully", id);
} else {
// Handle the case when the user does not exist (e.g., return an error response)
// You can throw an exception or return an appropriate response based on your application's requirements.
}
return "";
}
@PostMapping("create")
public User createUser(@RequestBody User user) {
return userRepository.save(user);
}
@GetMapping("get-single/{id}")
public User getUserById(@PathVariable Long id) {
// Use the UserRepository to fetch the user by ID
return userRepository.findById(id).orElse(null);
}
@PutMapping("/update/{id}")
public User updateUser(@PathVariable Long id, @RequestBody User updatedUser) {
// Check if the user with the specified ID exists
userRepository.findById(id).orElse(null);
// Set the ID of the updated user to the specified ID
updatedUser.setId(id);
// Save the updated user to the database
return userRepository.save(updatedUser);
}
}
DemoApplication.java (Run this file to serve spring boot application)
package com.javatest.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);
}
}
Got it ✅ Let’s build this from scratch, step by step, including MySQL dependency so you’re future-ready but you can still just run Hello World without DB config.
🚀 Spring Boot Hello World (with future MySQL support) in VS Code
CREATE TABLE `users` (
`id` int NOT NULL AUTO_INCREMENT,
`name` varchar(50) NOT NULL,
`age` int NOT NULL,
`city` varchar(50) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB;
React is a free and open-source front-end JavaScript library for building user interfaces based on UI components. It is maintained by Meta and a community of individual developers and companies. React can be used as a base in the development of single-page or mobile applications.
Create new react project
npm -v
npm i npx
npx create-react-app my-react-app
cd my-react-app
code .
Run from terminal
npm start
OR
npm start --port 8000
Open Browser and run the react app http://localhost:3000 OR http://ipaddress:3000
App.js
import logo from './logo.svg';
import './App.css';
function App() {
return (
<>
<h1>Test App</h1>
</>
);
}
export default App;
Create new component and use click and change event
src/components/Add.js
import { Fragment, useState } from "react";
function Add () {
const [ num1, setNum1 ] = useState(0);
const [ num2, setNum2 ] = useState(0);
const [ result, setResult ] = useState(0);
function addFun() {
setResult(num1 + num2);
}
return (<Fragment>
<h1>Addition of two numbers</h1>
<input type="text" onChange={ e => setNum1(parseInt(e.target.value)) }/>
<input type="text" onChange={ e => setNum2(parseInt(e.target.value)) } />
<button onClick={addFun}>Get Addtion</button>
<div>{result}</div>
</Fragment>);
}
export default Add;
Add this Add component in App component as tag <Add />
