What exactly is Ajax request? Is it different from Servlet Request?

Question

can anyone tell me. What exactly is Ajax request? Is it different from Servlet Request?

Answer 1

The problem is that, like so many terms used in IT¹ there is no clear definition of either an "AJAX request" or a "Servlet request". The best I can come up with this is:

• AJAX is short for "Asynchronous Javascript and XML", but these days the term is stretched to include JSON rather than XML. The key idea is that logic embedded in the web page (in Javascript) makes asynchronous HTTP requests back to the "home" server to request more information, rather than triggering a refresh of the entire webpage.

• An AJAX request is a request made by an AJAX application. Typically, it is an HTTP request made by (browser-resident) Javascript that uses XML to encode the request data and/or response data. The standard way of making an AJAX request in Javascript is to use an XmlHttpRequest object, but that is an implementation detail ... not fundamental to the definition of AJAX.

• A Servlet request is a request made to a Servlet. In theory it need not even be an HTTP request, since Servlet technology is (in theory) designed to work over other protocols as well. To my mind, this is not a particularly useful term.

So ... an AJAX request can be a Servlet request or not, and a Servlet request can be an AJAX request or not.

It is worth pointing out that there is a Java interface called ServletRequest that forms part of the J2EE APIs. This interface is a type of the object that is used to pass details of a web request around in a J2EE-based web application container. So when you see someone use the term "Servlet request" they may actually be talking about a ServletRequest instance.

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^{1 - Actually, this is no different from any other natural language. Words and phrases gain meaning depending on how people use them, not based on any definition you may find in a dictionary. The dictionary "definition" tends to arrive years or decades after a word or phrase comes into common usage, and it gives a meaning based how the word is (or was) used, rather than being a specification of a meaning.}