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A servlet acts as a bridge between web browsers and backend logic. It handles requests like logins, registrations, and data retrieval.
Many developers skip servlet fundamentals to learn Spring Boot. This is a mistake. Spring Boot runs on servlet containers like Tomcat. If you do not understand the lifecycle, you will face memory leaks and thread-safety issues.
The servlet container manages three main stages:
Initialization: The init() method The container loads the servlet class and creates one instance. The init() method runs only once. Use it to set up database connections or load configuration files. This prevents the server from reconnecting on every request.
Request Processing: The service() method Every client request triggers the service() method. It identifies the request type like GET or POST. It then sends the request to methods like doGet() or doPost().
Crucial Note on Scalability: The container does not create a new servlet object for every user. It creates one servlet object and uses multiple threads to handle many users.
- 100 Users = 1 Servlet Object + 100 Threads.
Because threads share the same servlet instance, avoid using instance variables for user data. Always use local variables to prevent data conflicts between users.
- Destruction: The destroy() method The container calls this method when the application stops. It runs only once. Use it to close database connections and release resources. This keeps your server stable.
Summary of the Lifecycle: โข init() runs once during setup. โข service() runs for every request. โข destroy() runs once during shutdown. โข The Container (Tomcat) manages everything.
Mastering these steps helps you build scalable, high-performance enterprise applications.
Source: https://dev.to/naveenkumar1/servlet-lifecycle-explained-with-practical-examples-41p
Optional learning community: https://t.me/GyaanSetuAi