json-to-xml()

Description

json-to-xml() parses a JSON string and converts it into an XML element tree following the W3C XSLT 3.0 specification for the JSON-to-XML mapping. Every JSON construct is represented as an element in the http://www.w3.org/2005/xpath-functions namespace: objects become <map> elements, arrays become <array> elements, strings become <string>, numbers become <number>, booleans become <boolean>, and null becomes <null>. Object keys are stored in a key attribute.

The result is a proper XML node tree, so it can be queried with standard XPath axis steps, processed with xsl:apply-templates, or further transformed. To go the other way (XML back to JSON text), use xml-to-json(). To obtain an XDM map/array instead of an XML tree, use parse-json().

Parameters

Return value

document-node()? — a document node whose root element is a <map>, <array>, or scalar element in the http://www.w3.org/2005/xpath-functions namespace, or empty sequence if the input is empty.

Examples

Converting a JSON object to XML and reading properties

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<data/>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:fn="http://www.w3.org/2005/xpath-functions">

  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/">
    <xsl:variable name="json"
      select="'{&quot;name&quot;:&quot;Alice&quot;,&quot;age&quot;:30,&quot;active&quot;:true}'"/>
    <xsl:variable name="xml" select="json-to-xml($json)"/>
    <person>
      <name><xsl:value-of select="$xml//fn:string[@key='name']"/></name>
      <age><xsl:value-of select="$xml//fn:number[@key='age']"/></age>
      <active><xsl:value-of select="$xml//fn:boolean[@key='active']"/></active>
    </person>
  </xsl:template>
</xsl:stylesheet>

Output:

<person>
  <name>Alice</name>
  <age>30</age>
  <active>true</active>
</person>

Converting a JSON array and applying templates to each member

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<report/>

Stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="3.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:fn="http://www.w3.org/2005/xpath-functions">

  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/">
    <xsl:variable name="json" select="unparsed-text('cities.json')"/>
    <xsl:variable name="xml" select="json-to-xml($json)"/>
    <cities>
      <xsl:apply-templates select="$xml/fn:array/fn:map"/>
    </cities>
  </xsl:template>

  <xsl:template match="fn:map">
    <city name="{fn:string[@key='city']}">
      <population><xsl:value-of select="fn:number[@key='pop']"/></population>
    </city>
  </xsl:template>
</xsl:stylesheet>

Assuming cities.json contains [{"city":"Paris","pop":2161000},{"city":"Lyon","pop":516092}]:

Output:

<cities>
  <city name="Paris">
    <population>2161000</population>
  </city>
  <city name="Lyon">
    <population>516092</population>
  </city>
</cities>

Notes

• The namespace URI for generated elements is http://www.w3.org/2005/xpath-functions. Bind it to a prefix (commonly fn) in your stylesheet to use axis steps efficiently.
• Object keys that are not valid XML NCName values are still stored verbatim in the key attribute; use @key = 'the-key' to match them.
• For deeply nested or large JSON structures, xsl:apply-templates with mode-based pattern matching is more maintainable than long // descendant paths.
• If you only need value access by key and not full axis navigation, parse-json() returning XDM maps and arrays is simpler.

See also

• xml-to-json()
• parse-json()
• json-doc()