Production-Grade Spring Boot APIs — Part 1: Web, JPA & What Really Happens at Startup

Most Spring Boot tutorials teach you how to build an API.

Very few explain what actually happens when a production Spring Boot application starts — and why those internals matter when systems grow.

This article documents how we actually understand and use Spring Boot foundations in real projects, not demo apps.

This is Part 1 of a 3-part series on Production-Grade Spring Boot API Design, written from real backend experience.

What this post covers

• Why spring-boot-starter-web exists

• starter vs starter-web

• ORM, JPA, Hibernate — without confusion

• Why Spring Data JPA removes DAOs & JDBC

• Spring Boot application lifecycle (startup to request handling)

• How DispatcherServlet fits into the picture

spring-boot-starter-web is the dependency that turns a plain Java application into a web‑ready REST API server.

It provides:

• Spring MVC

• Embedded web server (Tomcat by default)

• DispatcherServlet

• JSON serialization / deserialization

You do not configure servlets, servers, or JSON converters manually.

In production systems, this starter removes boilerplate and enforces convention over configuration.

spring-boot-starter vs spring-boot-starter-web

• spring-boot-starter

  • Core Spring features
  • Dependency Injection
  • Auto‑configuration
  • Logging (SLF4J + Logback)

• spring-boot-starter-web

  • Everything above plus
  • Spring MVC
  • Embedded server
  • REST API support

In short:

starter-web = starter + web capabilities

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2. ORM, JPA & Hibernate (Production clarity)

What is ORM?

ORM (Object Relational Mapping) is a technique that maps:

Java objects ⇄ Database tables

So instead of writing SQL, you work with Java objects.

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JPA vs Hibernate (Interview‑safe explanation)

• JPA

  • A specification (set of rules)
  • Defines annotations and interfaces
  • Does not generate SQL

• Hibernate

  • An implementation of JPA
  • Generates SQL
  • Talks to the database

In Spring Boot, we write code using JPA, while Hibernate does the heavy lifting.

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Why spring-boot-starter-data-jpa is critical

We never use JDBC directly in modern Spring Boot microservices.

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

This starter:

• Integrates Spring Data with JPA

• Uses Hibernate internally

• Provides repository abstractions

• Handles transactions automatically

Result: We persist Java objects without writing SQL or DAO classes.

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Repository abstraction (No DAO, No SQL)

public interface OrderRepository extends JpaRepository<OrderEntity, Long> {}

What this line really means:

“Spring, create a ready‑made database layer for this entity.”

Spring Data JPA:

• Generates implementation at runtime

• Provides CRUD, pagination, sorting

• Manages transactions

This is production‑grade abstraction, not magic.

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3. Spring Boot Application Lifecycle (What really happens)

┌─────────────────────────────┐
│        main() method        │
│ SpringApplication.run()     │
└──────────────┬──────────────┘
               ↓
┌─────────────────────────────┐
│   ApplicationContext        │
│        created              │
└──────────────┬──────────────┘
               ↓
┌─────────────────────────────┐
│     Component Scan          │
│  (@Service, @Controller)    │
└──────────────┬──────────────┘
               ↓
┌─────────────────────────────┐
│        Bean Creation        │
└──────────────┬──────────────┘
               ↓
┌─────────────────────────────┐
│   Dependency Injection      │
└──────────────┬──────────────┘
               ↓
┌─────────────────────────────┐
│   Embedded Server Starts    │
└──────────────┬──────────────┘
               ↓
┌─────────────────────────────┐
│ DispatcherServlet Ready 🚀  │
└─────────────────────────────┘

What matters in production

• Spring controls object creation (IoC)

• Dependencies are injected before usage

• Controllers are mapped after server startup

Developers write business logic — Spring handles infrastructure.

This is Part 1 of a 3-part series on Production-Grade Spring Boot API Design.

👉 Part 2 focuses on clean code structure, controllers, services, DTOs, and dependency injection.