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Spring Boot - How to Access Database using Spring Data JPA

Last Updated : 04 Sep, 2025
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Spring Data JPA simplifies database access by providing ready-to-use repositories for CRUD (Create, Read, Update, Delete) operations, reducing boilerplate code. In this article, we’ll demonstrate how to connect a database with a Spring Boot application using Spring Data JPA.

Step-by-Step Implementation

Step 1: Create a Spring Boot project

1. Go to Spring Initializr.

  • Project: Maven
  • Language: Java
  • Spring Boot Version: (latest stable)

2. Dependencies:

  • Spring Web -> To build REST APIs
  • Spring Data JPA -> For database access
  • MySQL Driver -> To connect with the MySQL database

Download the project and import it into your IDE (Eclipse/IntelliJ/STS).

Step 2: Configure Database Connection

Open the application.properties (or application.yml) file and configure the MySQL database connection:

Java 
spring.datasource.url=jdbc:mysql://localhost:3306/database_name
spring.datasource.username=root
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

Key Points:

  • Replace database_name with your actual database.
  • ddl-auto=update will create/update tables based on entity classes.
  • show-sql=true logs SQL queries in the console.

Step 3: Define the Entity Class

Now, create a model class Company that maps to the database table.

Company.java:

Java 
package com.example.demo.model;

import jakarta.persistence.*;

@Entity
@Table(name = "companies")
public class Company {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY) // MySQL-friendly
    private Integer id;

    private String name;
    private Integer duration;
    private String profile;
    private Integer stipend;

    @Column(name = "work_from_home")
    private Boolean workFromHome;

    public Company() {}

    public Company(String name, Integer duration, String profile, Integer stipend, Boolean workFromHome) {
        this.name = name;
        this.duration = duration;
        this.profile = profile;
        this.stipend = stipend;
        this.workFromHome = workFromHome;
    }

    // getters & setters
    public Integer getId() { return id; }
    public void setId(Integer id) { this.id = id; }

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    public Integer getDuration() { return duration; }
    public void setDuration(Integer duration) { this.duration = duration; }

    public String getProfile() { return profile; }
    public void setProfile(String profile) { this.profile = profile; }

    public Integer getStipend() { return stipend; }
    public void setStipend(Integer stipend) { this.stipend = stipend; }

    public Boolean getWorkFromHome() { return workFromHome; }
    public void setWorkFromHome(Boolean workFromHome) { this.workFromHome = workFromHome; }
}

Key Points:

  • The @Entity annotation marks this class as a JPA entity.
  • The @Id annotation specifies the primary key.
  • The @GeneratedValue(strategy = GenerationType.AUTO) annotation auto-generates the primary key value.

Step 4: Create the Repository Interface

Spring Data JPA provides repositories that reduce boilerplate CRUD code.

CompanyRepository.java:

Java 
package com.example.demo.repository;

import com.example.demo.model.Company;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface CompanyRepository extends JpaRepository<Company, Integer> {
}

Key Points:

  • The @Repository annotation marks this interface as a Spring Data repository.
  • CrudRepository<Company, Long> provides built-in methods like save(), findById(), findAll() and deleteById().

Step 5: Create REST Controller

Now, we will create REST APIs to perform CRUD operations on the Company entity.

CompanyController.java:

Java 
package com.example.demo.controller;

import com.example.demo.model.Company;
import com.example.demo.repository.CompanyRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.server.ResponseStatusException;

import java.util.List;

@RestController
@RequestMapping("/companies")
public class CompanyController {

    @Autowired
    private CompanyRepository companyRepository;

    // Home Page
    @GetMapping("/")
    public String welcome() {
        return "<html><body><h1>WELCOME</h1></body></html>";
    }

    // Get All Companies
    @GetMapping
    public List<Company> getAllCompanies() {
        return companyRepository.findAll();
    }

    // Get a Company by ID
    @GetMapping("/{id}")
    public Company getCompanyById(@PathVariable Integer id) {
        return companyRepository.findById(id)
                .orElseThrow(() -> new ResponseStatusException(HttpStatus.NOT_FOUND, "Company not found"));
    }

    // Create a Company
    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Company createCompany(@RequestBody Company company) {
        return companyRepository.save(company);
    }

    // Update a Company
    @PutMapping("/{id}")
    public Company updateCompany(@PathVariable Integer id, @RequestBody Company companyDetails) {
        Company company = companyRepository.findById(id)
                .orElseThrow(() -> new ResponseStatusException(HttpStatus.NOT_FOUND, "Company not found"));

        company.setName(companyDetails.getName());
        company.setDuration(companyDetails.getDuration());
        company.setProfile(companyDetails.getProfile());
        company.setStipend(companyDetails.getStipend());
        company.setWorkFromHome(companyDetails.getWorkFromHome());

        return companyRepository.save(company);
    }

    // Delete a Company
    @DeleteMapping("/{id}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void deleteCompany(@PathVariable Integer id) {
        if (!companyRepository.existsById(id)) {
            throw new ResponseStatusException(HttpStatus.NOT_FOUND, "Company not found");
        }
        companyRepository.deleteById(id);
    }
}

Key Points:

  • The @RestController annotation marks this class as a controller for handling REST requests.
  • The @RequestMapping("/companies") annotation maps all endpoints in this class to the /companies path.
  • The @Autowired annotation injects the CompanyRepository bean.

Step 6: Run & Test the Application

Start MySQL and create DB:

CREATE DATABASE database_name;

database

Run the Spring Boot App

DemoApplication.java:

Java 
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);
        System.out.println("" Spring Boot Application Started...");
    }
}

Now, we can run the spring boot application. we can test the REST APIs using Postman to verify that the application is functioning as expected

Testing with the POSTMAN collection

http://localhost:8080/companies/3

Testing
Testing with the POSTMAN

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