Spring Boot

Secret management (passwords, API keys, user ID...

1) Never hard-code or commit secrets Don’t put secrets in code, application.yml, or sample configs. Add to .gitignore: .env, *.secrets.yml, *.key, keystores. For local dev, load from env vars or...

Spring Bean Lifecycle

  What is a Spring Bean? A Spring Bean is simply an object that is managed by the Spring IoC container. In other words: any Java object that you register...

IoC Containers : ApplicationContext vs BeanFactory

  1. BeanFactory Definition: The simplest IoC container, responsible for instantiating, configuring, and managing beans. Features: Lazy initialization (bean created only when requested). Lightweight, suitable for simple applications with limited...

How a Spring Boot Application Works (Under the ...

1) Launch & bootstrap main() calls SpringApplication.run(App.class, args). SpringApplication decides the app type (Servlet/WebFlux/none), sets up Bootstrap logging, loads ApplicationContext type, banner, listeners, and default converters. 2) Create the ApplicationContext...

Spring Boot - Externalized Configuration

What it is: Spring Boot lets you keep settings (DB URLs, ports, feature flags, etc.) outside your code/jar so you can change behavior without rebuilding. Why it’s useful Different config...

Spring Boot Bean scopes

Default scope: singleton (one instance per Spring ApplicationContext). Spring reuses the same bean for every injection/call. Note: This is not the GoF Singleton pattern—each ApplicationContext has its own instance. Core...