Java Servlet

In the early days, web servers used to deliver
static contents that are indifferent to users' requests. But Now-a-days, Java servlets
are server-side programs (running inside a web server) that handle clients' requests and return a
customized or dynamic response for each request. The dynamic response could be based on user's input  (e.g., search, online shopping, online transaction) with data retrieved from databases or other applications, or time-sensitive data (such as news and stock prices).
Java servlets typically run on the HTTP protocol. HTTP is an
asymmetrical request-response protocol.The client sends a request message  to the server, and the server returns a response message  as illustrated.