parse-json()

Description

parse-json() converts a JSON string into XDM values following the mapping defined in the XPath 3.1 specification: JSON objects become XDM maps, JSON arrays become XDM arrays, JSON strings become xs:string, JSON numbers become xs:double, JSON booleans become xs:boolean, and JSON null becomes the empty sequence.

The optional options argument is an XDM map controlling parsing behavior. The most commonly used option is "liberal" (a boolean that allows relaxed JSON syntax), and "duplicates" (controlling how duplicate object keys are handled: "reject", "use-first", or "use-last").

The function is the inverse of xml-to-json() combined with parse-xml().

Parameters

Return value

item()? — an XDM map, array, string, double, boolean, or the empty sequence (for JSON null), depending on the JSON content.

Examples

Parsing a JSON object

Input XML:

<?xml version="1.0" encoding="UTF-8"?>
<data>
  <json>{"name": "Alice", "age": 30, "active": true}</json>
</data>

Stylesheet:

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

  <xsl:template match="/data">
    <xsl:variable name="obj" select="parse-json(json)"/>
    <person>
      <name><xsl:value-of select="map:get($obj, 'name')"/></name>
      <age><xsl:value-of select="map:get($obj, 'age')"/></age>
      <active><xsl:value-of select="map:get($obj, 'active')"/></active>
    </person>
  </xsl:template>
</xsl:stylesheet>

Output:

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

Parsing a JSON array

Stylesheet:

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

  <xsl:template match="/">
    <xsl:variable name="arr" select="parse-json('[1, 2, 3, 4, 5]')"/>
    <numbers>
      <xsl:for-each select="1 to array:size($arr)">
        <n><xsl:value-of select="array:get($arr, .)"/></n>
      </xsl:for-each>
    </numbers>
  </xsl:template>
</xsl:stylesheet>

Output:

<numbers>
  <n>1</n>
  <n>2</n>
  <n>3</n>
  <n>4</n>
  <n>5</n>
</numbers>

Notes

• JSON numbers are mapped to xs:double; large integers may lose precision. Use the "number-parser" option in XPath 3.1 to supply a custom number converter.
• JSON null maps to the empty sequence, not to a special null value. This means a JSON object with a null value and a missing key are indistinguishable after parsing with the default options.
• If the input string is not valid JSON, a dynamic error is raised unless "liberal": true() is set.
• The "duplicates" option defaults to "use-first" in most processors.

See also

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