I’m generating XML using JAXB and need specific namespace prefixes for my XML elements. Here’s an example of the XML structure I am currently generating, where each namespace has a unique prefix:

<ns4:RequestPayload 
    xmlns:head="urn:iso:std:iso:20022:tech:xsd:head.001.001.03" 
    xmlns:doc="urn:iso:std:iso:20022:tech:xsd:admi.004.001.02"  
    xmlns:ns4="urn:bceao:pi:xsd:payload.1.0.0" 
    xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    <head:AppHdr>
        <!-- Header info --> 
        <head:Sgntr>            
            <ds:Signature>
                <!-- Signature info --> 
            </ds:Signature>
        </head:Sgntr>
    </head:AppHdr>
    <doc:Document>
        <!-- Document info --> 
    </doc:Document>
</ns4:RequestPayload>

When I omit the prefix namespace declarations in my package-info.java, a default naming convention is applied, resulting in prefixes like ns1, ns2, ns3:

<ns4:RequestPayload 
    xmlns:ns1="urn:iso:std:iso:20022:tech:xsd:head.001.001.03" 
    xmlns:ns2="urn:iso:std:iso:20022:tech:xsd:admi.004.001.02"  
    xmlns:ns4="urn:bceao:pi:xsd:payload.1.0.0" 
    xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
    <ns1:AppHdr>
        <!-- Header info --> 
        <ns1:Sgntr>            
            <ds:Signature>
                <!-- Signature info --> 
            </ds:Signature>
        </ns1:Sgntr>
    </ns1:AppHdr>
    <ns2:Document>
        <!-- Document info --> 
    </ns2:Document>
</ns4:RequestPayload>

My goal is to generate an XML without any namespace prefixes, except for the “ds” prefix for the signature elements.

I tried overriding the getPreferredPrefix method in com.sun.xml.bind.marshaller.NamespacePrefixMapper to achieve the desired namespace prefix customization. Here is my implementation:

public class CustomNamespacePrefixMapper extends NamespacePrefixMapper {
    @Override
    public String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix) {
        if ("http://www.w3.org/2000/09/xmldsig#".equals(namespaceUri)) {
            return "ds";
        }
        return "";
    }
}

And adding to :

JAXBContext context = JAXBContext.newInstance(EnvelopeAdmi004.class);
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
marshaller.setProperty("com.sun.xml.bind.namespacePrefixMapper", new CustomNamespacePrefixMapper());

Despite this implementation, the output XML still contains default prefixes like ns1, ns2, and ns3. I expected that my custom NamespacePrefixMapper would result in an XML with no prefixes, except for the ds prefix for the signature elements.

How can I achieve the desired XML format with only the ds prefix and no other prefixes? What am I missing in my approach? Any suggestions or insights would be greatly appreciated.