XML vs JSON vs YAML — XML Tutorial

Side by side

<order id="1042"><customer>Ada</customer><item qty="2">Tea</item><item qty="1">Mug</item></order>

{"id": 1042, "customer": "Ada", "items": [{"name": "Tea", "qty": 2}, {"name": "Mug", "qty": 1}]}

id: 1042
customer: Ada
items:
  - {name: Tea, qty: 2}
  - {name: Mug, qty: 1}

	XML	JSON	YAML
Data types	Text (types come from a schema)	String, number, boolean, null, object, array	Like JSON, plus dates and more
Comments	Yes	No	Yes
Attributes vs children	Both	Only properties	Only keys
Mixed content (documents)	Natural	Awkward	Awkward
Schema and validation	DTD, XSD, RELAX NG, Schematron	JSON Schema	JSON Schema (usually)
Query and transform	XPath, XSLT, XQuery	JSONPath, jq	Converted to JSON first
Namespaces	Yes	No	No
Size and verbosity	Largest	Small	Smallest to type
Typical use	Documents, standards-based exchange, enterprise, Office/SVG	Web APIs, configuration	Configuration (Kubernetes, CI)

Converting XML to JSON

There is no single correct mapping: you must decide how attributes, repeated elements, text and types become JSON. Write the mapping explicitly for your data:

XML to JSON with an explicit mappingTry it yourself

import json
from lxml import etree

order = etree.fromstring(b'<order id="1042"><customer>Ada</customer><item qty="2">Tea</item><item qty="1">Mug</item></order>')
data = {
    "id": int(order.get("id")),
    "customer": order.findtext("customer"),
    "items": [{"name": i.text, "qty": int(i.get("qty"))} for i in order.findall("item")],
}
print(json.dumps(data, separators=(",", ":")))

Output

{"id":1042,"customer":"Ada","items":[{"name":"Tea","qty":2},{"name":"Mug","qty":1}]}

XML to JSON with an explicit mappingTry it yourself

<?php
$order = simplexml_load_string('<order id="1042"><customer>Ada</customer><item qty="2">Tea</item><item qty="1">Mug</item></order>');
$data = [
    "id" => (int) $order['id'],
    "customer" => (string) $order->customer,
    "items" => [],
];
foreach ($order->item as $item) {
    $data["items"][] = ["name" => (string) $item, "qty" => (int) $item['qty']];
}
echo json_encode($data), "\n";

Output

{"id":1042,"customer":"Ada","items":[{"name":"Tea","qty":2},{"name":"Mug","qty":1}]}

XML to JSON with an explicit mapping

import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.*;
import java.io.ByteArrayInputStream;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        String xml = "<order id=\"1042\"><customer>Ada</customer><item qty=\"2\">Tea</item><item qty=\"1\">Mug</item></order>";
        Element order = DocumentBuilderFactory.newInstance().newDocumentBuilder()
            .parse(new ByteArrayInputStream(xml.getBytes("UTF-8"))).getDocumentElement();
        List<String> items = new ArrayList<>();
        NodeList nodes = order.getElementsByTagName("item");
        for (int i = 0; i < nodes.getLength(); i++) {
            Element item = (Element) nodes.item(i);
            items.add("{\"name\":\"" + item.getTextContent() + "\",\"qty\":" + Integer.parseInt(item.getAttribute("qty")) + "}");
        }
        String customer = order.getElementsByTagName("customer").item(0).getTextContent();
        System.out.println("{\"id\":" + Integer.parseInt(order.getAttribute("id")) + ",\"customer\":\"" + customer
            + "\",\"items\":[" + String.join(",", items) + "]}");
    }
}

import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.*;
import java.io.ByteArrayInputStream;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        String xml = "<order id=\"1042\"><customer>Ada</customer><item qty=\"2\">Tea</item><item qty=\"1\">Mug</item></order>";
        Element order = DocumentBuilderFactory.newInstance().newDocumentBuilder()
            .parse(new ByteArrayInputStream(xml.getBytes("UTF-8"))).getDocumentElement();
        List<String> items = new ArrayList<>();
        NodeList nodes = order.getElementsByTagName("item");
        for (int i = 0; i < nodes.getLength(); i++) {
            Element item = (Element) nodes.item(i);
            items.add("{\"name\":\"" + item.getTextContent() + "\",\"qty\":" + Integer.parseInt(item.getAttribute("qty")) + "}");
        }
        String customer = order.getElementsByTagName("customer").item(0).getTextContent();
        System.out.println("{\"id\":" + Integer.parseInt(order.getAttribute("id")) + ",\"customer\":\"" + customer
            + "\",\"items\":[" + String.join(",", items) + "]}");
    }
}

Output

{"id":1042,"customer":"Ada","items":[{"name":"Tea","qty":2},{"name":"Mug","qty":1}]}

Run this on your computer — see “Get Started” for setup.

In real Java code use Jackson (jackson-dataformat-xml) instead of building JSON by hand; the hand-written version above only keeps the example free of dependencies.

Generic converters (Python's xmltodict, or PHP's json_encode(simplexml_load_string(...))) are quick but lossy and inconsistent: one <item> becomes an object while two become an array, and every value is a string.

Choosing

Public web or mobile API: JSON.
Configuration edited by people: YAML or TOML (JSON if it's generated).
Documents with markup, standards that mandate XML (finance, healthcare, government, publishing), strict schema-validated contracts, or XSLT pipelines: XML.
Don't convert working XML integrations to JSON for fashion; do validate whatever you accept.

Side by side

Converting XML to JSON

Choosing

Test yourself