Querying JSON with XSLT, XPath, XQuery

Learn how XPath, XSLT, and XQuery can be used to query JSON documents or transform JSON data to other formats, such as ...

Querying JSON with XSLT, XPath, and XQuery

While XSLT, XPath, and XQuery are traditionally associated with XML, there are ways to work with JSON data using similar concepts. Below is an overview of how to query JSON data using these technologies.

1. Understanding JSON and Its Structure

JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write and easy for machines to parse and generate. A typical JSON structure looks like this:

{
  "books": [
    {
      "title": "Learning XQuery",
      "author": "John Doe",
      "price": 29.99
    },
    {
      "title": "Mastering XPath",
      "author": "Jane Smith",
      "price": 19.99
    }
  ]
}

2. Querying JSON with XPath

XPath is primarily designed for XML, but some JSON processing tools allow the use of XPath-like syntax to query JSON. For example, with tools like JSONPath, you can use similar expressions.

Example JSONPath Query:

To retrieve all book titles:

$.books[*].title

3. Querying JSON with XQuery

XQuery can also be used to query JSON, especially with implementations that support JSON data types and structures, such as MarkLogic.

Example XQuery Query:

Assuming you have JSON data stored in a variable:

let $json := '{"books":[{"title":"Learning XQuery","author":"John Doe","price":29.99},{"title":"Mastering XPath","author":"Jane Smith","price":19.99}]}'
return
  for $book in json:parse($json)/books/book
  return $book/title

4. Querying JSON with XSLT

XSLT is primarily for XML, but you can convert JSON to XML first, then use XSLT to query the data. This is less common and more complex due to the need for conversion.

Example Workflow:

1. Convert JSON to XML: Use a library or service to convert your JSON into XML format.

2. XSLT Transformation: Once in XML format, you can apply XSLT to query the data.

Example XML (Converted from JSON):

<books>
  <book>
    <title>Learning XQuery</title>
    <author>John Doe</author>
    <price>29.99</price>
  </book>
  <book>
    <title>Mastering XPath</title>
    <author>Jane Smith</author>
    <price>19.99</price>
  </book>
</books>

XSLT Example:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
  <xsl:template match="/">
    <xsl:for-each select="books/book">
      <title><xsl:value-of select="title"/></title>
    </xsl:for-each>
  </xsl:template>
</xsl:stylesheet>

Conclusion

While XSLT is not natively designed for JSON, XPath can be applied through JSONPath-like syntax, and XQuery can be adapted for querying JSON data, especially in environments supporting it. Understanding how to work with these technologies in relation to JSON can enhance your data processing capabilities. If you have further questions or need examples, feel free to ask!