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Please dont bash me for asking. I can't find any information that can help me understand this.

I've been programming for two years and I still have never had to use JSON nor XML. What can I do with JSON or XML what I can't do with a database? Do we just use them as configuration files?

user1534664
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    To transfer data between applications or in files. – SLaks Apr 21 '13 at 21:09
  • See also: http://stackoverflow.com/questions/383692/what-is-json-and-why-would-i-use-it and http://stackoverflow.com/questions/3536893/what-are-the-pros-and-cons-of-xml-and-json. – alecxe Apr 21 '13 at 21:14
  • @SLaks Thanks dude, thats what I needed. I didn't understand all the verbose articles. – user1534664 Apr 21 '13 at 21:22

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XML and JSON are generic serialization formats. You can use them whenever you want to exchange data between applications in a simple way. You don't need to invent your own file format. You can use standardized infrastructure (serializers, libraries).

For example, how would you send a structured piece of data (e.g. information about a sale or a customer) to a 3rd party? You would need to agree on a data format. XML and JSON are handy for that. You can easily generate JSON and the other developer will immediately understand its structure and be able to deserialize it using very little code.

usr
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  • Good info, thanks dude. But I still have some questions. So XML and JSON are used for sharing data with 3rd parties and other programs? Like the youtube feeds? – user1534664 Apr 21 '13 at 21:34
  • Yes, that's one important application. You can also store data for yourself for later use, of course. The key question is: How would you exchange or store data *without* these formats? You'd have to roll your own format for very little benefit. (Or use a database, but that is something entirely different). – usr Apr 21 '13 at 22:09
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While the other answer is essentially correct (both are generic options for data exchange), it is worth noting that there are a few important differences. XML was built to handle documents. JSON is built to describe objects.

  1. Character coding, parsing and validation. XML is built to let parsers handle this automatically, JSON not so much.
  2. Simplicity, compactness. XML simply cannot do this nearly as well as JSON.

Therefore, if you have to write something which will dump the data to a file and the file is transferred sans any meta data (describing mime type, character coding or other conventions), XML may be a superior approach because you can embed the necessary meta data in the data using appropriate declarations (and namespaces). This is especially important when it comes to "documents": JSON simply does not have the primitives to describe locale very well and there is no sane standard way to do it that will be understood by all parsers. Therefore if someone did something incredibly silly like converting your UTF-8 coded JSON string to Shift-JIS, well good luck getting any parser to understand that in a generic fashion. XML solves that (and it also provides for language support).

On the other hand if all you ever want to do is exchange a bunch of objects in a highly controlled setting (i.e. character coding, language etc. are all well defined parameters) and you therefore do not have to worry about arbitrary weirdness coming your way -- then JSON offers a much more compact serialisation format, which is also (probably) easier to read for most programmers. Finally JSON is particularly amenable to web applications, because it happens to be valid JavaScript all by itself. While treating JSON as part of your JavaScript code using something like eval, is not a good security practice for consuming arbitrary JSON; it can help to simplify the "getting up and running" stage of any front end for a web application which you do have full control over (all you would need to do is `eval' it, though again for code which has to work with arbitrary JSON this is a terrible idea because that could expose you to security vulnerabilities of other sites as well as your own).

user268396
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  • I'm giving you the accepted answer because with the additional details you also helped me understand the difference between XML and json better. Thanks :) – user1534664 Apr 21 '13 at 21:51
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As a real-life example, I used to work on an iOS app that interacted with a Ruby on Rails server. The server had an SQL database and a lot of the logic for the app. The server took requests from the iOS client, retrieved and operated on the pertinent data and then rendered the result as JSON, sending it back to the client to use for whatever. It was an easy way for the Ruby server application to yield data to the Objective-C iOS app.

davetakahashi
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