Spring Data with Spring Boot: Scalable API Tutorial

In today’s fast-paced software landscape, building scalable, maintainable, and data-driven backend systems is a strategic advantage. Spring Boot and Spring Data JPA offer a powerful combination for Java developers aiming to deliver robust RESTful APIs with minimal boilerplate and maximum flexibility. In this post you will see how to work with spring boot spring data inventory management.

Whether you’re modernizing legacy platforms, architecting microservices, or building AI-powered applications, mastering Spring Boot and Spring Data can dramatically accelerate your backend development.

Why Spring Boot + Spring Data?

Spring Boot simplifies application setup and deployment, while Spring Data JPA abstracts away the complexities of data access. Together, they enable:

• Rapid development of RESTful APIs
• Clean separation of concerns
• Auto-generated queries and repository implementations
• Seamless integration with relational databases like PostgreSQL, MySQL, and H2
• Scalable architecture for enterprise-grade systems

What Is Spring Data JPA?

Spring Data JPA is a part of the larger Spring Data ecosystem. It provides:

• Repository Abstraction: Define interfaces, and Spring auto-generates implementations.
• Query Derivation: Write methods like findByEmailAndStatus()—no SQL required.
• Custom Queries: Use @Query for native SQL or JPQL when needed.
• Pagination & Sorting: Built-in support for pageable APIs.
• Auditing: Track creation and modification timestamps effortlessly.

Quickstart: Spring Boot + Spring Data Setup

Let’s say you’re building a customer management API. Here’s how easy it is to get started:

Entity Class

@Entity
public class Customer {
    @Id @GeneratedValue
    private Long id;
    private String name;
    private String email;
    private String status;
}

@Entity
public class Customer {
    @Id @GeneratedValue
    private Long id;
    private String name;
    private String email;
    private String status;
}

Repository Interface

public interface CustomerRepository extends JpaRepository<Customer, Long> {
    List<Customer> findByStatus(String status);
    Optional<Customer> findByEmail(String email);
}

public interface CustomerRepository extends JpaRepository<Customer, Long> {
    List<Customer> findByStatus(String status);
    Optional<Customer> findByEmail(String email);
}

REST Controller

@RestController
@RequestMapping("/customers")
public class CustomerController {

    @Autowired
    private CustomerRepository repository;

    @GetMapping("/active")
    public List<Customer> getActiveCustomers() {
        return repository.findByStatus("ACTIVE");
    }

    @GetMapping("/email")
    public ResponseEntity<Customer> getByEmail(@RequestParam String email) {
        return repository.findByEmail(email)
                         .map(ResponseEntity::ok)
                         .orElse(ResponseEntity.notFound().build());
    }
}

@RestController
@RequestMapping("/customers")
public class CustomerController {

    @Autowired
    private CustomerRepository repository;

    @GetMapping("/active")
    public List<Customer> getActiveCustomers() {
        return repository.findByStatus("ACTIVE");
    }

    @GetMapping("/email")
    public ResponseEntity<Customer> getByEmail(@RequestParam String email) {
        return repository.findByEmail(email)
                         .map(ResponseEntity::ok)
                         .orElse(ResponseEntity.notFound().build());
    }
}

Real-Life Use Case: spring boot spring data inventory management for a furniture store

Imagine you’re building an inventory management system for a growing furniture retailer. The system must:

• Track stock levels across multiple warehouses
• Support product search and filtering
• Trigger restocking alerts
• Integrate with supplier APIs
• Expose RESTful endpoints for mobile apps and POS systems

Domain Model

@Entity
public class FurnitureItem {
    @Id @GeneratedValue
    private Long id;
    private String name;
    private String category;
    private int quantity;
    private String location;
    private LocalDate lastRestocked;
}

@Entity
public class FurnitureItem {
    @Id @GeneratedValue
    private Long id;
    private String name;
    private String category;
    private int quantity;
    private String location;
    private LocalDate lastRestocked;
}

Repository Interface

public interface FurnitureRepository extends JpaRepository<FurnitureItem, Long> {
    List<FurnitureItem> findByCategoryAndLocation(String category, String location);

    @Query("SELECT f FROM FurnitureItem f WHERE f.quantity < :threshold")
    List<FurnitureItem> findLowStock(@Param("threshold") int threshold);
}

public interface FurnitureRepository extends JpaRepository<FurnitureItem, Long> {
    List<FurnitureItem> findByCategoryAndLocation(String category, String location);

    @Query("SELECT f FROM FurnitureItem f WHERE f.quantity < :threshold")
    List<FurnitureItem> findLowStock(@Param("threshold") int threshold);
}

REST API

@RestController
@RequestMapping("/inventory")
public class InventoryController {

    @Autowired
    private FurnitureRepository repository;

    @GetMapping("/low-stock")
    public List<FurnitureItem> getLowStockItems(@RequestParam int threshold) {
        return repository.findLowStock(threshold);
    }

    @GetMapping("/search")
    public List<FurnitureItem> searchByCategoryAndLocation(
        @RequestParam String category,
        @RequestParam String location) {
        return repository.findByCategoryAndLocation(category, location);
    }
}

@RestController
@RequestMapping("/inventory")
public class InventoryController {

    @Autowired
    private FurnitureRepository repository;

    @GetMapping("/low-stock")
    public List<FurnitureItem> getLowStockItems(@RequestParam int threshold) {
        return repository.findLowStock(threshold);
    }

    @GetMapping("/search")
    public List<FurnitureItem> searchByCategoryAndLocation(
        @RequestParam String category,
        @RequestParam String location) {
        return repository.findByCategoryAndLocation(category, location);
    }
}

Business Logic Extensions

• Scheduled Restock Alerts: Use Spring Scheduler to check low-stock items daily.
• Supplier Integration: Trigger external API calls when restock thresholds are breached.
• Audit Trail: Add @CreatedDate and @LastModifiedDate for tracking changes.
• Security: Protect endpoints with Spring Security and role-based access control.

Advanced Tips for Spring Data Power Users

• Use Specifications for dynamic query building
• Integrate QueryDSL or Criteria API for complex filtering
• Add DTO projections for lightweight responses
• Enable Spring Data REST for auto-generated HATEOAS-compliant endpoints
• Combine with Spring Cache for performance optimization

Summary

Spring Boot and Spring Data JPA are not just productivity boosters—they’re strategic enablers for building clean, scalable, and maintainable backend systems. Whether you’re building internal tools, customer-facing APIs, or AI-powered services, mastering these technologies will elevate your backend engineering game.

If you’re ready to take it further, consider integrating predictive modeling, GenAI workflows, or RAG pipelines into your Spring Boot architecture. The possibilities are endless—and the foundation starts here.

While you are here, maybe try one of my apps for the iPhone.

Snap! I was there on the App Store

Listed below are the links to the first two parts of this series

How to build a blog engine with React & Spring Boot – Part 1 – My Day To-Do (mydaytodo.com)

How to build a blog engine with React & Spring Boot – Part 2 – My Day To-Do (mydaytodo.com)

Here are some of my other bloposts,

How to unit test react-redux app – My Day To-Do (mydaytodo.com)