CODEWITHSUNDEEP
javaxml
Doug
Doug

Reputation: 7107

Control order of XML attributes in outputed file in Java

How do I control the order that the XML attributes are listed within the output file?

It seems by default they are getting alphabetized, which the program I'm sending this XML to apparently isn't handling.

e.g. I want zzzz to show first, then bbbbb in the following code.

DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
Document doc = docBuilder.newDocument();
Element root = doc.createElement("requests");
doc.appendChild(root);
root.appendChild(request);
root.setAttribute("zzzzzz", "My z value");
root.setAttribute("bbbbbbb", "My b value");

TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
DOMSource source = new DOMSource(doc);
StreamResult result = new StreamResult(new File(file));
transformer.transform(source, result);

Upvotes: 3

Views: 5221

Answers (4)

trallnag
trallnag

Reputation: 2386

If you don't want to use another framework just for a custom attribute order you can simply add an order identifier to the attributes.

<someElement a__price="32" b__amount="3"/>

After the XML serializer is done post process the raw XML like so:

public static String removeAttributeOrderIdentifiers(String xml) {
    return xml.replaceAll(
        " [a-z]__(.+?=\")", 
        "$1"
    );
}

And you will get:

<someElement amount="3" price="32"/>

Upvotes: 0

John Jerik
John Jerik

Reputation: 39

XML Canonicalisation results in a consistent attribute ordering, primarily to allow one to check a signature over some or all of the XML, though there are other potential uses. This may suit your purposes.

Upvotes: 0

Alexandr
Alexandr

Reputation: 9515

I had the same issue when I used XML DOM API for writing file. To resolve the problem I had to use XMLStreamWriter. Attributes appear in a xml file in the order you write it using XMLStreamWriter.

Upvotes: 2

Michael Kay
Michael Kay

Reputation: 163655

The order of attributes is defined to be insignificant in XML: no conformant XML application should produce results that depend on the order in which attributes appear. Therefore, serializers (code that produces lexical XML as output) will usually give you no control over the order.

Now, it would sometimes be nice to have that control for cosmetic reasons, because XML is designed to be human-readable. So there's a valid reason for wanting the feature. But the fact is, I know of no serializer that offers it.

Upvotes: 3

Related Questions