Real World Example

Most Indian product companies (Flipkart, Paytm, Zerodha, Razorpay) run Spring Boot services on MySQL or PostgreSQL, with H2 or Testcontainers in tests. The pattern is the same as below: entity + repository + service, with config per environment.

@Service
@Transactional
public class ProductService {
    private final ProductRepository repo;
    private final ProductMapper mapper;

    public ProductService(ProductRepository repo, ProductMapper mapper) {
        this.repo = repo;
        this.mapper = mapper;
    }

    @Transactional(readOnly = true)
    public Page<ProductResponse> search(String q, Pageable pageable) {
        Page<Product> page = (q == null || q.isBlank())
                ? repo.findAll(pageable)
                : repo.findByNameContainingIgnoreCase(q, pageable);
        return page.map(mapper::toResponse);
    }

    public ProductResponse create(CreateProductRequest req) {
        if (repo.existsBySku(req.sku())) throw new DuplicateSkuException(req.sku());
        return mapper.toResponse(repo.save(mapper.toEntity(req)));
    }
}

@GetMapping
public Page<ProductResponse> search(@RequestParam(required = false) String q,
                                    @PageableDefault(size = 20, sort = "name") Pageable pageable) {
    return service.search(q, pageable);
}

curl -X POST localhost:8080/api/products -H "Content-Type: application/json" -d '{"sku":"ELE-1002","name":"Wireless Keyboard","description":"Hindi + English keys","price":1299.00,"stock":60,"category":"Electronics"}'
curl "localhost:8080/api/products?q=wireless&page=0&size=2&sort=price,desc"

{"id":3,"sku":"ELE-1002","name":"Wireless Keyboard","description":"Hindi + English keys","price":1299.00,"stock":60,"category":"Electronics","inStock":true}
{"content":[{"id":3,"sku":"ELE-1002","name":"Wireless Keyboard","description":"Hindi + English keys","price":1299.00,"stock":60,"category":"Electronics","inStock":true},{"id":1,"sku":"ELE-1001","name":"Wireless Mouse","description":"2.4 GHz, silent clicks","price":799.00,"stock":120,"category":"Electronics","inStock":true}],"page":{"size":2,"number":0,"totalElements":2,"totalPages":1}}

What Hibernate sent to MySQL (with show-sql: true):

Hibernate: select count(*)>0 from products p1_0 where p1_0.sku=?
Hibernate: insert into products (category,description,name,price,sku,stock) values (?,?,?,?,?,?)
Hibernate: select p1_0.id,p1_0.category,p1_0.description,p1_0.name,p1_0.price,p1_0.sku,p1_0.stock from products p1_0 where upper(p1_0.name) like upper(?) escape '\' order by p1_0.price desc limit ?,?