Internet is a global system of interconnected computer networks that connect various Domain Name System (DNS) servers, web hosting servers, home and business users, etc. Internet is a network of networks.
Lot of data transfer happens in an internet between computers and networks, and there should be some rules to regulate these transfers. A communications protocol is a system of digital rules for data exchange within or between computers.
Similar to scope and lifetime of variables in Java as you have seen in blocks-and-methods-in-java, parameters and attributes in a Java EE web application also have scope and lifetime in the context of the web application. The scope of a parameter/attribute denotes the availability of that parameter/attribute for use. A web application serves multiple requests from clients when it is up and running. These requests can be from same client or different clients.
A servlet is a java class that conform to the servlet specification and need to be deployed to a servlet container to work as a servelt. A servlet’s life cycle consist of Servlet class loading, Servlet instantiation, and then methods init(), service() and destroy().
HTTP is a synchronous request-response application network protocol. Client sends a request specifying one of the seven HTTP methods, the location of the resource to be invoked, a set of optional headers and an optional message body. The server sends back a response containing the version of HTTP we are using, a response code, a description of the response code, a set of optional headers, and an optional message body. HTTP is the primary protocol for most web applications on the Internet, regardless of whether they are written in Java, PHP or ASP.
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