Difference Between Servlet and JSP

Key Difference between Servlet and JSP

• Servlet can accept all protocol requests, including HTTP, while JSP can only accept HTTP requests.
• In MVC architecture, the Servlet works as a controller, while JSP works as a view for displaying output.
• Servlet should be used when there is more data processing involved, whereas JSP is generally used when there is less involvement in data processing.
• Servlets run faster than JSP; on the other hand, JSP runs slower than Servlet as it takes time to compile the program and convert it into servlets.
• You can override the service() method in Servlet, but in JSP, you can’t override the service() method.
• In Servlet, you have to implement both business logic and presentation logic in a single file. Whereas in JSP, business logic is split from presentation logic using JavaBeans.

What is Servlet?

Servlet technology, a key part of Java’s toolbox, thrives under the watchful eyes of something called a servlet engine which takes care of it. Imagine a tool that not only cooks up instant, lively updates but also chats you up by tossing questions your way then catching your replies. Servlet extends the functionality of a web server. Though servlets can respond to many types of requests, they generally implement web containers for hosting any website on a web server. Therefore, it is qualified as a server-side servlet web API.

Difference between Servlet vs JSP

Based on my experience, here are the main differences between Servlet and JSP:

Servlet	JSP
Servlets run faster than JSP.	JSP runs slower than Servlet as it takes time to compile the program and convert it into servlets.
It is hard to write code in Servlet.	It’s easier to code in JSP compared to servlets.
In MVC architecture, Servlet works as a controller.	In MVC architecture, JSP works as a view for displaying output.
It should be used when there is more data processing involved.	JSP is generally used when there is no involvement of much data processing.
There is no custom tag writing facility in servlets.	You can easily build custom tags that can directly call Java beans.
Servlet is a java code.	JSP is a HTML-based code.
It’s ready to handle any kind of protocol request, HTTP included.	It’s set up to only handle HTTP requests.
You can override the service() method.	In JSP, you can’t override the service() method.
In Servlet, by default, session management is not enabled; the user has to enable it explicitly.	In JSP, session management is automatically enabled.
In Servlet, you have to implement both business logic and presentation logic in a single file.	In JSP, business logic is split from presentation logic using JavaBeans.
Modification in the Servlet file is time-consuming due to reloading, recompiling, and restarting the server.	JSP modification is fast, as you just need to click on the refresh button.

Why I use Servlet?

From my experience, here are the reasons we use Servlet:

• The performance is much better.
• Servlet is used when you do not like to create a separate process to handle each and every request of the client.
• Developers can use servlets when they have to take advantage of all the features of Java.
• Java class libraries, which are available to a servlet, can communicate with applets, databases, or other software via RMI and socket mechanisms.

Why I use JSP?

Here are the reasons I prefer JSP:

• In Java server pages JSP, the execution is much faster compared to other dynamic languages.
• It is much better than Common Gateway Interface (CGI).
• Java server pages (JSP) are always compiled before it’s processed by the server as it reduces the effort of the server to create process.
• Java server pages are built over Servlets API. Hence, it has access to all Java APIs, JNDI, JDBC EJB, and other components of Java.
• JSP is an important part of Java EE (Enterprise Edition), which is a platform for enterprise-level applications.

Servlet Life Cycle

Servlet life cycle is depicted in the below diagram:

1) Start: Execution of servlet begins.

2) Loading & instantiation void init(): It is called when servlet is first loaded. This method lets you initialize Servlet.

3) Initialized void service(): The purpose of this method is to serve a request. You can call it as many times as you like.

4) Handling request and destroying Servlet: Java application must first determine what code is needed to execute the request URL to provide a response. To destroy the servlet Void destroy method is used at the end of the servlet life cycle.

5) End of Request Thread: When service() finishes its task, either the thread ends or returns to the thread pool that is managed by the servlet container.

6) End: Servlet lifecycle finishes.

7) Stop: Servlet stop executing.

JSP Life Cycle

JSP life cycle is depicted in the diagram below:

1. Translation of JSP page into a servlet.
2. Compilation of JSP page(Compilation of JSP page into _jsp.java)
3. Classloading (_jsp.java is converted to class file _jsp.class)
4. Instantiation(Object of generated servlet is created)
5. Initialisation(_jspinit() method is invoked by container)
6. Request Processing(_jspservice() method is invoked by the container)
7. Destroy (_jspDestroy() method invoked by the container)