Backend frameworks

Spring

The backbone of enterprise Java. Spring Boot makes Java web apps approachable with auto-configuration, dependency injection, REST controllers and Spring Data JPA — production-grade out of the box.

Demo 01

Spring Initializr — build a project

Every Spring app starts at start.spring.io. Pick your dependencies, click generate, and watch the project skeleton stream in.

Dependencies:

Spring Web — REST controllers & embedded Tomcat Spring Data JPA — repositories & ORM H2 Database — in-memory dev DB Spring Security — auth & access control

Demo 02

A @RestController returns JSON

Annotations do the heavy lifting. @RestController + @GetMapping map an HTTP request to a Java method. Send a request and see the simulated response.

Endpoints: /api/products, /api/products/{id}, /api/health

@RestController
@RequestMapping("/api/products")
public class ProductController {

    private final ProductRepository repo;

    @GetMapping
    public List<Product> all() {
        return repo.findAll();
    }

    @GetMapping("/{id}")
    public Product one(@PathVariable Long id) {
        return repo.findById(id).orElseThrow();
    }
}

Demo 03

Spring Data JPA repositories

Declare an interface method name and Spring writes the query for you. Pick a repository method and see the result table + the SQL Spring generates.

public interface ProductRepository
        extends JpaRepository<Product, Long> {

    List<Product> findByInStockTrue();
    List<Product> findByPriceLessThan(double price);
}

Demo 04

Dependency injection in action

Spring's IoC container creates and wires your objects (beans). You never call new for a service — you ask for it, Spring supplies it. Watch the container boot.

// startup log appears here…

Demo 05

Why Spring?

The default choice for serious Java backends.

Auto-configuration — Spring Boot wires sensible defaults so you write almost no setup.

Dependency injection — loosely-coupled, testable components via the IoC container.

Vast ecosystem — Security, Data, Cloud, Batch, Kafka — one consistent programming model.

Battle-tested — runs huge portions of the enterprise & banking world.

The Initializr generator, REST endpoint console, JPA repository table and DI boot log are simulated with vanilla JavaScript — real Spring runs Java on a JVM server (embedded Tomcat) with a real database. The code blocks show genuine Java/Spring Boot syntax. The shared CSS shell provides page styling.

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