Visualizing the lifecycle of a request in a Servlet/JSP environment. Understanding the critical difference between the "First Load" compilation and the optimized "Hot Path".
Before analyzing the flow, we must define the roles. In this architecture, strict separation of concerns allows for scalable applications.
The entry point for all requests (e.g., ChatServlet.java). It handles business logic, processes input, and selects the appropriate View.
The data structure (e.g., Mensaje.java). It holds the state of the application, such as the list of chat messages, independent of the UI.
The presentation layer (e.g., chat.jsp). It is purely for rendering HTML. Crucially, it compiles into a Servlet behind the scenes.
This scenario occurs only the first time a JSP is requested (or after a server restart). The system must perform "Just-In-Time" work to convert the human-readable JSP into executable Java bytecode.
Step 5 in this flow represents a significant performance hit compared to standard requests. The JSP engine must translate tags into Java code, compile that code, and load the class into memory.
A huge portion of the initial load time is spent on the Translation & Compilation phase.
User accesses /chat.
Tomcat invokes ChatServlet.doGet().
Servlet prepares session data.
Control transfers to chat.jsp.
JSP -> .java -> .class
The server pauses to build the servlet.
The new _chat_jsp.class runs.
HTML sent to browser.
Form submission to /chat.
ChatServlet.doPost() called.
Message added to list.
No compilation. _chat_jsp.class is reused immediately.
This is the standard operating mode. Once the JSP is compiled, it behaves exactly like a compiled Java Servlet. The "Heavy Lifting" of text parsing is gone.
Subsequent requests skip the most expensive step, resulting in drastically lower latency.
Designers work on JSP (HTML), Developers work on Servlet (Java). Code is cleaner and easier to maintain.
After the initial compilation hit, JSPs are as fast as native Servlets because they become native Servlets.
The Web Container (Tomcat) handles the compilation, loading, and instantiation automatically.