How can I maintain XML attribute order after DOM processing?

XML Attribute Order After DOM Processing

When working with XML files using the standard Document Object Model (DOM), maintaining attribute order during serialization back to XML is not guaranteed. This can be problematic for situations where attribute order is crucial.

The reason behind this issue lies in DOM's design. It treats attributes as unordered collections, disregarding their sequence. When the XML is serialized, the attributes are written in an arbitrary order.

Possible Solutions

There are two approaches to address this issue:

1. Using SAX (Simple API for XML)

SAX-based parsers, unlike DOM, provide a way to preserve attribute order. By utilizing a SAX parser, it is possible to control the sequence in which attributes are written to the resulting XML.

2. Custom XSLT Transformation Stylesheet

Alternatively, you can create a custom XSLT transformation stylesheet to specify the desired attribute order. This involves defining output templates that explicitly specify the sequence of attributes.

Reasons for Preserving Attribute Order

While some argue that attribute order is irrelevant in XML, there are legitimate reasons to preserve it:

• Regression Testing: Verifying XML output differences can be easier with maintained attribute order.
• Human Readability: Keeping attributes in their original order improves the readability and maintainability of the XML file, especially for configuration files edited manually.
• Third-Party Tools: Some XML handling tools, such as XML editors, may rely on attribute order for proper functioning.

Example Using SAX

The following SAX code snippet can be used to preserve attribute order during serialization:

SAXParserFactory spf = SAXParserFactoryImpl.newInstance();
spf.setNamespaceAware(true);
spf.setValidating(false);
spf.setFeature("http://xml.org/sax/features/validation", false);
spf.setFeature("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false);
spf.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
SAXParser sp = spf.newSAXParser() ;
Source src = new SAXSource ( sp.getXMLReader(), new InputSource( input.getAbsolutePath() ) ) ;
String resultFileName = input.getAbsolutePath().replaceAll(".xml$", ".cooked.xml" ) ;
Result result = new StreamResult( new File (resultFileName) ) ;
TransformerFactory tf = TransformerFactory.newInstance();
Source xsltSource = new StreamSource( new File ( COOKER_XSL ) );
xsl = tf.newTransformer( xsltSource ) ;
xsl.setParameter( "srcDocumentName", input.getName() ) ;
xsl.setParameter( "srcDocumentPath", input.getAbsolutePath() ) ;

xsl.transform(src, result );

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