How to Convert JSON to XML using XSLT 2.0

XSLT 2.0 is powerful enough to process even non-XML input. For example, I have created a transformation that converts JSON text to well structured XML output:

JSON text:

{
     "firstName": "John",
     "lastName": "Smith",
     "age": 25,
     "address": {
         "streetAddress": "21 2nd Street",
         "city": "New York",
         "state": "NY",
         "postalCode": "10021"
     },
     "phoneNumber": [
         { "type": "home", "number": "212 555-1234" },
         { "type": "fax", "number": "646 555-4567" }
     ]
}

It works by employing XML Pipeline technique:

• first mode parses text using regular expressions and generates sequence of tokens in XML format: <comment>, <string>, <number>, <symbol>{</symbol>, etc.
• second mode groups all tokens between “{” and “}” symbols into <object> element, between “[” and “]” symbols into <array> element
• third mode makes a <field> element from <string><symbol>:<symbol>(<string>|<number>|<object>|<array>) sequence
• fourth mode drops comma between consecutive <field> elements

and finally it performs XSD validation check.

This approach is quite exotic and non-standard, because when people hear word “parsing” they think of BNF, state-machine, AST, YACC, etc., but these technologies were created to parse complex programming languages.

I claim that XSLT coupled w/ regexp as tokenizer is powerful enough to convert simple markup languages such as JSON, CSS, MIF, RTF, wiki, etc., into XML.