Spring Boot application with H2 in-memory database and CRUD (Create, Read, Update, Delete) operations

Category : Spring Boot | Sub Category : Spring Boot | By Prasad Bonam Last updated: 2023-08-07 13:17:56 Viewed : 346

Here is a complete example of a Spring Boot application with H2 in-memory database and CRUD (Create, Read, Update, Delete) operations for a Student entity.

1. Create a Spring Boot Project: Start by creating a new Spring Boot project using Spring Initializr or your preferred IDE. Include the following dependencies: Spring Web, Spring Data JPA, H2 Database, and Thymeleaf (for simple UI).

2. Configure Application Properties: Open the src/main/resources/application.properties file and add the following configuration:

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# H2 Configuration
spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.h2.console.enabled=true

# JPA Configuration
spring.jpa.hibernate.ddl-auto=update

3. Create the Entity Class: Create a Student entity class in the package com.example.demo.model:

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package com.example.demo.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;
    private int age;

    // Constructors, getters, setters
}

4. Create the Repository Interface: Create a repository interface in the package com.example.demo.repository:

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package com.example.demo.repository;

import com.example.demo.model.Student;
import org.springframework.data.jpa.repository.JpaRepository;

public interface StudentRepository extends JpaRepository<Student, Long> {
}

5. Create the Service Class: Create a service class in the package com.example.demo.service:

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package com.example.demo.service;

import com.example.demo.model.Student;
import com.example.demo.repository.StudentRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class StudentService {
    @Autowired
    private StudentRepository studentRepository;

    public List<Student> getAllStudents() {
        return studentRepository.findAll();
    }

    public Optional<Student> getStudentById(Long id) {
        return studentRepository.findById(id);
    }

    public Student createStudent(Student student) {
        return studentRepository.save(student);
    }

    public Student updateStudent(Long id, Student updatedStudent) {
        if (studentRepository.existsById(id)) {
            updatedStudent.setId(id);
            return studentRepository.save(updatedStudent);
        }
        return null;
    }

    public void deleteStudent(Long id) {
        studentRepository.deleteById(id);
    }
}

6. Create the Controller: Create a controller class in the package com.example.demo.controller:

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package com.example.demo.controller;

import com.example.demo.model.Student;
import com.example.demo.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@Controller
@RequestMapping("/students")
public class StudentController {
    @Autowired
    private StudentService studentService;

    @GetMapping
    public String getAllStudents(Model model) {
        List<Student> students = studentService.getAllStudents();
        model.addAttribute("students", students);
        return "student-list";
    }

    @GetMapping("/{id}")
    public String getStudentById(@PathVariable Long id, Model model) {
        studentService.getStudentById(id).ifPresent(student -> model.addAttribute("student", student));
        return "student-details";
    }

    @GetMapping("/add")
    public String showAddForm(Model model) {
        model.addAttribute("student", new Student());
        return "student-form";
    }

    @PostMapping("/add")
    public String addStudent(@ModelAttribute Student student) {
        studentService.createStudent(student);
        return "redirect:/students";
    }

    @GetMapping("/edit/{id}")
    public String showEditForm(@PathVariable Long id, Model model) {
        studentService.getStudentById(id).ifPresent(student -> model.addAttribute("student", student));
        return "student-form";
    }

    @PostMapping("/edit/{id}")
    public String editStudent(@PathVariable Long id, @ModelAttribute Student updatedStudent) {
        studentService.updateStudent(id, updatedStudent);
        return "redirect:/students";
    }

    @GetMapping("/delete/{id}")
    public String deleteStudent(@PathVariable Long id) {
        studentService.deleteStudent(id);
        return "redirect:/students";
    }
}

7. Create HTML Templates (Thymeleaf): Create Thymeleaf HTML templates in the src/main/resources/templates directory:

   • student-list.html (List all students):

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<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Student List</title>
</head>
<body>
    <h1>Student List</h1>
    <table border="1">
        <tr>
            <th>ID</th>
            <th>Name</th>
            <th>Age</th>
            <th>Actions</th>
        </tr>
        <tr th:each="student : ${students}">
            <td th:text="${student.id}"></td>
            <td th:text="${student.name}"></td>
            <td th:text="${student.age}"></td>
            <td>
                <a th:href="@{/students/{id}(id=${student.id})}">View</a>
                <a th:href="@{/students/edit/{id}(id=${student.id})}">Edit</a>
                <a th:href="@{/students/delete/{id}(id=${student.id})}">Delete</a>
            </td>
        </tr>
    </table>
    <br>
    <a href="/students/add">Add Student</a>
</body>
</html>

• student-details.html (View student details):

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<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Student Details</title>
</head>
<body>
    <h1>Student Details</h1>
    <p>ID: <span th:text="${student.id}"></span></p>
    <p>Name: <span th:text="${student.name}"></span></p>
    <p>Age: <span th:text="${student.age}"></span></p>
    <a href="/students">Back to List</a>
</body>
</html>

• student-form.html (Add/Edit student form):

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<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title th:if="${student.id} ? `Edit Student` : `Add Student`"></title>
</head>
<body>
    <h1 th:if="${student.id}">Edit Student</h1>
    <h1 th:unless="${student.id}">Add Student</h1>
    <form th:if="${student.id}" th:action="@{/students/edit/{id}(id=${student.id})}" th:object="${student}" method="post">
        <input