JSP - Life Cycle

A JSP page goes through the following phases from first request to destruction:

1. Translation Phase — .jsp → .java (servlet source)
2. Compilation Phase — .java → .class (bytecode)
3. Servlet Class Loading — load the generated class into the container
4. Servlet Instantiation — create an instance of the generated servlet
5. jspInit() — called once for initialization
6. _jspService() — called for every request
7. jspDestroy() — called once before the servlet is taken out of service

For the first request — all phases execute in order (translation, compilation, loading, instantiation, jspInit, _jspService).

For subsequent requests — only _jspService() is called (since the servlet is already loaded and initialised).

JSP will participate in the Translation Phase in the following cases:

• At the time of the first request
• If the source code of the JSP has been modified compared to earlier requests. The JSP Engine uses a tool (like ARAXIS) to compare timestamps of the .class and .jsp files.

For the first request, the following activities are performed:

1. Translation
2. Compilation
3. Class Loading
4. Instantiation
5. jspInit()

For the second request onwards, only _jspService() is executed.

This means the first request is slower than subsequent requests.

To overcome this problem, we can use pre-compilation of JSP.

Invoke the JSP with the special query parameter:

The jsp_precompile=true request is not a real request to the JSP — it only performs pre-compilation. This triggers:

1. Translation
2. Compilation
3. Class Loading
4. Instantiation
5. jspInit()

Then, when the first real request arrives, only _jspService() executes.

The main advantage: all requests (including the first) are processed with uniform response time. The expensive translation and compilation happen before any real user hits the page.

A JSP page can contain the following elements: