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POShould JSON null be preserved?
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copied!<p>I tried to convert the JSON data</p> <pre><code>{ "a": { "b": null } } </code></pre> <p>to XML using <a href="http://jsontoxml.utilities-online.info/" rel="nofollow noreferrer">an online converter</a>. The response was</p> <pre><code><a> <b /> </a> </code></pre> <p>Converting this back to JSON using the same converter gave me</p> <pre><code>{ "a": { } } </code></pre> <p>This made me wonder – if you're explicitly given a null value, are you required to preserve it when dealing with JSON? I'm fairly sure that the XML <code><a><b /></a></code> is <em>not</em> equivalent to <code><a></a></code>, and especially not <code><a /></code> (which happens to be what I get when I continue with the same exercise).</p> <p>In other words, if I'm handed JSON of unknown origin and am supposed to hand it over to an unknown recepient, am I required to preserve the nulls or can I safely remove them? Conversely, can I rely on my nulls to end up in the same way I outputted them when delivered by third-party software?</p> <p>Here's a similar question: <a href="https://stackoverflow.com/questions/11003424/should-json-include-null-values">Should JSON include null values</a> – However, the question there is whether the code should output nulls if <em>you define the format</em> yourself, not what you should do if you don't know anything about the original format.</p> <p><strong>EDIT – Clarification:</strong> The way I asked the question was bad and apparently caused confusion. To rephrase it: I <em>do</em> understand that XML and JSON are different formats and are able to carry different kinds of (meta)data. I <em>do</em> know that <strong>null</strong> is a valid value, as defined by <a href="http://www.ietf.org/rfc/rfc4627.txt?number=4627" rel="nofollow noreferrer">RFC4627</a>. I <em>do</em> understand that there are different ways to convert between XML and JSON since the formats don't have a 1-to-1 relationship. I <em>do</em> understand that the converter I found might be buggy. However, the fact that the <em>same</em> converter didn't provide the same conversion in both directions (no information was lost when converting from <code>"b": null</code> to <code><b /></code> and a similar translation in the opposite direction would have been possible) made me wonder something that I couldn't find an answer to despite attempts:</p> <ul> <li>Is it legal, according to the JSON standard, to treat <code>{"a":{"b":null}}</code> and <code>{"a":{}}</code> as one and the same object when transferring them on behalf of other software?</li> </ul> <p>Note that I'm here assuming that it's legal to add or remove whitespace as I see fit (e.g. pretty-printing, which is okay according to RFC4627), and even to rearrange the name/value pairs in a collection (again according to RFC4627). I simply don't know if a <strong>null</strong> must be preserved in the same way as significant data, or can be dropped in the same way as insignificant whitespace.</p>

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