Spring Data

What is Spring Data?

Spring Data is a Spring-based framework designed to simplify database access and data management in Java applications. It provides a consistent and easy-to-use API for working with SQL and NoSQL databases, reducing the need for boilerplate code when interacting with databases.

🌟 Key Features of Spring Data

✔ Eliminates Boilerplate Code – No need to write complex DAO implementations.
✔ Supports Multiple Databases – Works with SQL (JPA, JDBC) and NoSQL (MongoDB, Redis, Cassandra, etc.).
✔ Repository Abstraction – Uses the Spring Data Repository pattern to simplify database queries.
✔ Built-in Query Methods – Supports derived queries (e.g., findByName() automatically generates SQL).
✔ Pagination and Sorting – Provides built-in support for handling large datasets.

🛠️ Spring Data Components

Spring Data consists of multiple modules for different databases:

🚀 Hands-on: Using Spring Data JPA in a Spring Boot Application

Let’s build a simple Spring Boot + Spring Data JPA example using MySQL.

1️⃣ Add Dependencies (Maven)

In pom.xml, add:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

2️⃣ Configure Database (application.properties)

Set up MySQL connection in src/main/resources/application.properties:

spring.datasource.url=jdbc:mysql://localhost:3306/mydatabase
spring.datasource.username=root
spring.datasource.password=yourpassword
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

3️⃣ Create Entity Class

Define a User entity:

import jakarta.persistence.*;

@Entity
@Table(name = "users")
public class User {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;
    private String email;

    // Constructors, Getters, and Setters
}

4️⃣ Create Repository Interface

Spring Data JPA automatically provides CRUD operations for the entity.

import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Long> {
    User findByEmail(String email);  // Spring Data will generate the query automatically
}

5️⃣ Create a REST Controller

Expose API endpoints using Spring Boot REST Controller:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/users")
public class UserController {

    @Autowired
    private UserRepository userRepository;

    @GetMapping
    public List<User> getAllUsers() {
        return userRepository.findAll();
    }

    @PostMapping
    public User createUser(@RequestBody User user) {
        return userRepository.save(user);
    }
}

6️⃣ Run and Test the Application

• Start the Spring Boot app using: mvn spring-boot:run
• Test API in Postman or Browser:
  • GET All Users → http://localhost:8080/users
  • POST New User (Body: JSON) { "name": "John Doe", "email": "john@example.com" }

🎯 Why Use Spring Data?

✔ No Boilerplate Code – No need to write DAO classes manually.
✔ Built-in Query Methods – Queries like findByEmail() are automatically generated.
✔ Works with Both SQL & NoSQL – Supports relational and NoSQL databases.
✔ Integrated with Spring Boot – Works seamlessly with the Spring ecosystem.

Would you like an example of Spring Data with MongoDB or a custom query example with JPQL? 🚀