JEE specifications or technologies in this layer receive requests from the web server and send back the response, typically in HTML format. However, it is also possible to return only data from the presentation layer, for example in JavaScript Object Notation (JSON) or eXtensible Markup Language (XML) format, which could be consumed by Asynchronous JavaScript and XML (AJAX) calls to update only part of the page, instead of rendering the entire HTML page. Classes in the presentation layer are mostly executed in the web container—it is a part of the application server that handles web requests. Tomcat is an example of a popular web container.
Now let's take a look at some of the specifications in this layer.
