Java Bean Bag

🧪🧠 TDD vs BDD & 🤔 Why Interviewers Ask “Which Design Pattern Are You Using?” Two interview questions that look simple… but silently decide your fate. 😄☕ If you’re a Java / Spring Boot developer and you’ve attended even 2–3 interviews , you’ve definitely heard these questions: ❓ “Are you using TDD or BDD?” ❓ “What design pattern are you using in your project?” And suddenly your brain goes like… 🧠 “Wait… we are just writing code da… what pattern??” Don’t worry. This blog will spoon-feed you the answer 👶🥄 — slowly, clearly, and in an interview-safe way. 🧪 Question 1: TDD vs BDD – What are you really doing? 🤯 Dumb Question: “Both are testing… then why two names?” 💡 Brilliant Answer (Baby Explanation): Think like this 👇 TDD BDD Developer talking to code 🧑‍💻➡️💻 Business talking to system 🧑‍💼➡️🖥️ 🔵 TDD – Test Driven Development 🧪 👶 One-line concept: Write test first ❌, then write code ✔, then clean it 🔄 @Test...

Handling Transactions in Thread-Based Environments (Java + Spring Boot) 🧠 How Do You Handle Transactions in a Thread-Based Environment? (The ultimate fresher-friendly explanation — with jokes, questions & real-life pain 😂) 1️⃣ First — Why This Question Comes in EVERY Interview? Interviewer thinking: “If this candidate can’t handle concurrent transactions, I’ll hire him and later he’ll break my production database.” 😭 You thinking: “Why this fellow always asking this tough question?” 😫 Reality: 👉 In real applications multiple threads hit the system. 👉 Multiple users click at the same time. 👉 If your code is not transaction-safe, DB becomes “Kaboom 💥”. That’s why interviewers ask: “How do you handle transactions in multi-threaded scenarios?” Because they want to check: ✔ Do you understand data consistency? ✔ Do you know why @Transactional exists?...

🍃 What is MongoDB? MongoDB is a NoSQL document-based database that stores data in JSON-like format. Instead of rows and columns, it uses collections and documents . This makes it super flexible and schema-less — perfect for fast-moving modern apps 🚀. 💡 Difference vs SQL Databases: SQL = Tables, Rows, Columns 📊 MongoDB = Collections, Documents 📚 ❓Why Indexes Matter Imagine searching a phonebook without alphabetical order — painful, right? 😅 Indexes make your searches faster by letting MongoDB skip scanning every document. ⚡ Tip: Without indexes, MongoDB performs a collection scan — meaning it checks every record. That’s fine for 10 docs... not for 10 million! 🧠 Types of Indexes in MongoDB 1️⃣ Single Field Index Most basic and common. You index one field. db.users.createIndex({ "name": 1 }) 1 = ascending , -1 = descending . Used for queries like { name: "Priya" } . 2️⃣ Compound Index Multiple fields combined to improve multi-fi...

🐱 Tomcat vs ⚡ Netty – Which One Should You Use? So recently I got curious about this too 🤔. Everywhere in Spring Boot tutorials we see Tomcat . Then suddenly while exploring Spring WebFlux , the name Netty pops up. And I was like – “Wait, who’s this Netty guy trying to replace Tomcat?” 😅 Let’s break it down with real-time examples , icons , and fun comparisons . 🐱 Tomcat – The Traditional Web Server Type: Servlet Container (blocking I/O) World: Used with Spring MVC Style: Thread-per-request model 👩‍💻 Pros: Stable, widely used, battle-tested Cons: Struggles with huge concurrent connections 👉 Example in real life: Tomcat is like a restaurant with fixed waiters 🍴. - Each customer = one thread/waiter - If too many customers come in at once → waiters run out → customers wait outside 🚪 ⚡ Netty – The Reactive Rockstar Type: Asynchronous Event-Driven Network Framework World: Default for Spring WebFlux Style: Event-lo...

🚀 Spring Batch – Beginner’s Guide with Real-Time Example Ever wondered how large amounts of data are processed in batches, like a boss? 😎 Welcome to Spring Batch – your friend when you need reliable, fast, and scalable batch processing in Java! 1️⃣ What is Spring Batch? 🤔 A framework to process large volumes of data efficiently. Handles batch jobs, transactions, retries, skip logic, and chunk-based processing . Perfect for ETL jobs, report generation, invoice processing – basically, anything your database hates if you run it all at once 😂. 2️⃣ Important Concepts & Flow 🔄 Core Components: Job – The whole batch process (like a movie 🎬). Step – A phase of a job (like a scene in that movie). ItemReader – Reads data from source (DB, CSV, API…think Sherlock reading clues 🕵️‍♂️). ItemProcessor – Processes/validates data (Sherlock deduces 🔍). ItemWriter – Writes data to destination (He reports findings ✉️). Flow: Cont...

🌟 My Understanding on AOP in Spring Boot AOP = Aspect-Oriented Programming 🧩 AOP is like OOP concepts but works on an Aspect model . It was developed for handling common logic like security 🔒, logging 📝, transactions 💰, caching 🗃️, scheduling ⏰, and metrics 📊. These are called cross-cutting concerns . 📌 Core Terms Aspect: A module containing cross-cutting logic (@Aspect class). Join Point: A point during execution of a program, e.g., method call. Pointcut: Expression that defines where the aspect applies. Advice: Action taken at a join point, e.g., logging before a method. Proxy: Wrapper around the actual object that intercepts calls. 📌 Types of Advice Advice Type When it Runs @Before Before method execution @After After method execution (regardless of outcome) @AfterReturning After method successfully returns @AfterThrowing After method throws exception @Around Wraps method execution (before + after) ⚙ How AOP Works Internally in Spring Boot S...