Advance java session 2
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Servlets allow Java code to generate dynamic web content. They have an initialize, service, and destroy lifecycle. Servlets are more efficient than CGI as they are lightweight Java threads that can handle multiple requests, remain in memory, and cache computations. They also have built-in support for parsing requests and setting responses that CGI relies on external libraries for.
Advance java session 2
- 2. Agenda • Introduction to Java Servlets • Servlet Life Cycle • Describe web applications, CGI, and the role of Java • Describe benefits of Java servlet technology • Create a simple Java Servlet
- 3. Introduction to Java Servlets • Read explicit data sent by client (form data) • Read implicit data sent by client (request headers) • Generate the results • Send the explicit data back to client (HTML) • Send the implicit data to client (status codes and response headers)
- 5. Servlets LifeCycle • A servlet passes through the following stages in its life. - Initialize - Service - Destroy
- 6. Servlet’s Life Cycle (Cont)
- 7. Characteristic of Init() stage • Executed once, when the servlet gets loaded for the first time • Not called for each client request • The above two points make it an ideal place to perform the startup tasks which are done in constructor in a normal class.
- 8. Characteristic of service() stage • service() method is the engine of the servlet • It is executed per request in a separate Thread • Hence faster and efficient than CGI • It is an important method to be overridden in GenericServlet
- 9. Benefits of Servlets • Efficient - Servlets are light weight java threads and not a process like CGI - For each request there would be a n no of threads for n no of requests but only a single Object of a Servlet class - When CGI finishes handling request the program terminates making difficult to cache computations ,keep connection open etc - Servlets remain in the memory even after the response is complete.
- 10. Benefits of Servlets • Convenient - Servlets have an extensive infrastructure for • Parsing and decoding • Reading and setting http headers • Handling cookies • Tracking sessions - In CGI we have to depend on Perl for such tasks
- 11. Benefits of Servlets • Powerful - Servlets support several capabilities like • Communicating with Web Server • Translate relative URL’s to concrete Path • Sharing data • Connection Pooling and optimization - In CGI we have to user server specific API
- 12. Benefits of Servlets • Portability - Servlets are written in java and can be deployed in Multiple Servers • Secure - Being written entirely in java. - Does not rely on O/S shell as CGI
- 13. Summary • Demonstrate a simple Servlet example • Overview the Life cycle of a servlet • Benefits of Servlet compared to CGI