To improve development efficiency of Web Application, we need to implement the parallel development between Web Front End and Web Back End. To achieve this goal, first we should determine the data exchange format between Web Front End and Web Back End. In this article, let’s talk about some data exchange formats between them.

Common data exchange formats between Web Front End and Web Back End are as below:
XML
XML stands for EXtensible Markup Language
XML is a markup language much like HTML
XML was designed to carry data, not to display data
XML tags are not predefined. You must define your own tags
XML is designed to be self-descriptive
XML is a W3C Recommendation

JSON
JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999.

XML and JSON, both can be used as data exchange formats. Let’s compare their main advantages and disadvantages between them.
XML
Advantage
XML is better for human reading than JSON.

Disadvantage
XML is not lighter as JSON.

JSON
Advantage
JSON is lighter than XML.

Disadvantage
JSON is not better for human reading as XML.

In my opinion, JSON is a great data exchange format for Web Applications over browsers. It is not the question of XML vs. JSON. It is the question of When XML and When JSON.

From: Jacky Cui's Java Home: Data Exchange Format between Web Front End and Web Back End