java - JAXB: How to avoid repeated namespace definition for xmlns:xsi

Question

I have a JAXB setup where I use a @XmlJavaTypeAdapter to replace objects of type Person with objects of type PersonRef that only contains the person's UUID. This works perfectly fine. However, the generated XML redeclares the same namespace (xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance") every time it's used. While this is generally okay, it just doesn't feel right.

How can I configure JAXB to declare xmlns:xsi at the very beginning of the document? Can I manually add namespace declarations to the root element?

Here's an example of what I want to achive:

Current:

<person uuid="6ec0cf24-e880-431b-ada0-a5835e2a565a">
    <relation type="CHILD"> 
        <to xsi:type="personRef" uuid="56a930c0-5499-467f-8263-c2a9f9ecc5a0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/> 
    </relation> 
    <relation type="CHILD"> 
        <to xsi:type="personRef" uuid="6ec0cf24-e880-431b-ada0-a5835e2a565a" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/> 
    </relation>
    <!-- SNIP: some more relations -->
</person>

Wanted:

<person uuid="6ec0cf24-e880-431b-ada0-a5835e2a565a" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <relation type="CHILD"> 
        <to xsi:type="personRef" uuid="56a930c0-5499-467f-8263-c2a9f9ecc5a0"/> 
    </relation> 
    <relation type="CHILD"> 
        <to xsi:type="personRef" uuid="6ec0cf24-e880-431b-ada0-a5835e2a565a"/> 
    </relation>
    <!-- SNIP: some more relations -->
</person>

Answer 1

Not that pretty but you could add an empty schemaLocation to the root element:

marshaller.setProperty(Marshaller.JAXB_SCHEMA_LOCATION, "");