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Servlet Roadmap

Here’s a complete Servlet Roadmap — perfect for understanding how to work with Java Servlets for web development, especially if you're aiming to build Java EE or Jakarta EE web applications.

🧭 Java Servlet Roadmap

✅ 1. Prerequisites

Before diving into Servlets, make sure you're comfortable with:

  • Core Java (OOP, collections, exception handling)
  • Basic HTML/CSS
  • HTTP Protocol (methods like GET, POST, etc.)
  • IDE setup (IntelliJ/Eclipse)
  • Basic Maven or Gradle usage
  • Understanding of web servers (Tomcat, Jetty)

✅ 2. Introduction to Servlets

  • What is a Servlet?
  • Servlet vs JSP vs Frameworks
  • Role of a Servlet container (e.g., Apache Tomcat)
  • Servlet lifecycle (init(), service(), destroy())

✅ 3. Servlet Setup

  • Create a simple servlet

  • Web deployment using:

    • web.xml (deployment descriptor)
    • @WebServlet annotation (Servlet 3.0+)

  • Directory structure of a Java web project (WEB-INF, webapp, etc.)

  • Deploy WAR to Tomcat

✅ 4. Handling HTTP Requests & Responses

  • Understanding HttpServletRequest and HttpServletResponse
  • doGet() vs doPost()
  • Handling form data (query params, form POST)
  • Setting content types and response headers
  • Redirect vs Forward

✅ 5. ServletConfig and ServletContext

  • What is ServletConfig and how to use it
  • What is ServletContext and application-level data sharing
  • Init parameters from web.xml

✅ 6. Session Management

  • HTTP is stateless — why sessions are needed
  • Cookies vs URL rewriting vs Hidden Form Fields
  • HttpSession usage (getSession(), invalidate(), setAttribute())
  • Session timeout and tracking

✅ 7. Request Dispatching

  • RequestDispatcher usage

    • Forward
    • Include

  • Chaining servlets and JSPs

  • Including static content

✅ 8. File Upload and Download

  • Multipart form data parsing (Apache Commons FileUpload or Servlet 3.0+ Part)
  • Downloading files using streams
  • MIME types and headers for file operations

✅ 9. Error Handling in Servlets

  • Handling exceptions with web.xml <error-page>
  • Custom error messages
  • Logging exceptions (using Logger or SLF4J)

✅ 10. Filters and Listeners

  • Servlet Filters (pre-processing/post-processing requests)

    • Authentication, logging, compression, etc.

  • Servlet Listeners

    • Lifecycle hooks: context, session, attribute events

✅ 11. Servlet Best Practices

  • Avoid storing sensitive data in plain request/response
  • Thread safety — avoid shared mutable state
  • Proper session handling
  • Use logging libraries
  • Modular project structure with MVC approach

✅ 12. Integrating with JSP

  • When and how to use JSP with Servlets
  • Forwarding from Servlet to JSP for view rendering
  • Expression Language (EL) and JSTL basics

✅ 13. Servlet Security (Basic)

  • Authentication and authorization via web.xml
  • Securing URLs
  • HTTPS and secure cookies
  • Form-based login

✅ 14. Moving Beyond

After mastering Servlets, you can level up with:

  • JSP & JSTL (if not yet)
  • MVC frameworks: Spring MVC, JSF
  • Hibernate or JPA for DB interaction
  • RESTful services using JAX-RS or Spring Boot
  • Jakarta EE for modern enterprise development

🧩 Suggested Tools & Libraries

  • Apache Tomcat (Servlet container)
  • Maven for dependency management
  • SLF4J + Logback for logging
  • Postman or cURL for testing HTTP requests
  • MySQL or H2 for DB integration

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