An 8-week journey

Java backend, told as a story.

From the 1970s to Spring Boot — every annotation, every layer, every odd pattern explained as the answer to a problem that came before. Theory first. Code second. Built for an L1→L2 developer aiming to be interview-ready in two months.

56 days~6 hrs per day1 serious projectemployable goal

How this handbook works

Every concept is taught the same way: what existed before, what pain triggered the change, and what shifted. No concept is introduced in isolation. Each one is a reaction to something that came before it.

What we go deep on

Spring Core (IoC, DI, AOP)
Spring Boot & auto-configuration
Spring Data JPA & Hibernate
REST API design
Transactions, validation, security
The Webhook Relay project

What we cover conceptually

Servlets — diagrams, no real coding
JSP — historical bridge only
Raw JDBC — one day of hands-on, then move on
EJBs — story only, no code

⚙️ The locked decision

Project: Webhook Relay. One real, production-realistic backend with live event streaming, retries with exponential backoff, idempotency keys, and a replay endpoint. Built in weeks 5–7.

The 8-week map

Weeks 1 and 2 are fully written. Click any day to begin. Later weeks unlock as you progress.

Week 1 · Foundations

Java refresher & reading fluency

Story of Java backend, JVM internals, OOP re-examined, Collections internals, generics, Java 8 features, exceptions.

Days 1–7 · all written ✓

Week 2 · Web + data

HTTP, SQL, JDBC, Servlets, REST

HTTP deep dive, SQL essentials and transactions, raw JDBC pain, Servlets walkthrough, REST architecture, JSP historical tour.

Days 8–14 · all written ✓

Week 3 · Spring core

IoC, DI, beans, AOP

The core insight that defines Spring, bean lifecycle, AOP & proxies, configuration styles, validation.

Days 15–21

Week 4 · Boot + JPA

Spring Boot & persistence

Auto-configuration demystified, ORM & Hibernate, Spring Data JPA, transactions deep, REST controllers.

Days 22–28

Week 5 · Project v1

Webhook Relay — MVP

Receive endpoint, persistence, dashboard skeleton, WebSocket live stream, basic forwarding.

Days 29–35

Week 6 · Project v2

Reliability & replay

Async queues, exponential backoff, dead-letter queue, replay endpoint, idempotency, rate limiting.

Days 36–42

Week 7 · Production

Auth, observability, deploy

JWT auth, multi-tenancy, OpenAPI docs, testing strategy, observability, Docker, deployment.

Days 43–49

Week 8 · Interview

Sharpening & mock rounds

System design applied to project, top Spring/JPA/HTTP/REST questions, mock interviews, applying.

Days 50–56

Week 1 — Foundations

Day 01The Story of Java backend — Why everything looks the way it does (1970s → today)→Day 02How Java actually runs — JVM, bytecode, classloader — just enough to demystify Spring→Day 03OOP re-examined — Abstract vs interface, marker interfaces, when to use what→Day 04Collections internals — ArrayList vs LinkedList vs HashMap — the why behind every choice→Day 05Generics & type safety — What <T> actually does, type erasure, wildcards, PECS→Day 06Java 8 reading fluency — Streams, lambdas, Optional — fluently read modern Spring code→Day 07Exceptions done right — Checked vs unchecked, design rules, the controversy→

Week 2 — Web + Data

Day 08HTTP, deeply — Methods, status codes, headers, idempotency — the protocol every API speaks→Day 09SQL essentials — The relational mental model, joins, indexes — interview-grade→Day 10SQL deeper — Transactions, isolation levels, cascades, the four anomalies→Day 11Raw JDBC — feel the pain — One full hands-on day. Connections, statements, the boilerplate Spring saves you from→Day 12Servlets — concept walkthrough — Lifecycle, dispatch, sessions, filters — diagrammed, not coded→Day 13REST architecture — What 'RESTful' actually means — Fielding's six constraints, Richardson maturity→Day 14JSP — historical tour — How server-rendered HTML worked. Why it died. What replaced it.→