How to configure JAXB so it trims whitespaces when unmarshalling tag value?

Use a custom Adapter class. I was thinking that NormalizedStringAdapter would do the work but it's only for unmarshaling and it doesn't do what you want anyway.

public class MyNormalizedStringAdapter extends XmlAdapter<String, String> {

    @Override
    public String marshal(String text) {
        return text.trim();
    }

    @Override
    public String unmarshal(String v) throws Exception {
        return v.trim();
    }
}

then decorate the field with your adapter like this:

@XmlElement(required=true)
@XmlJavaTypeAdapter(MyNormalizedStringAdapter.class)
String name;

To remove leading and trailing whitespaces during unmarshalling you can use an adapter CollapsedStringAdapter (since Java 1.6).

Built-in XmlAdapter to handle xs:token and its derived types. This adapter removes leading and trailing whitespaces, then truncate any sequnce of tab, CR, LF, and SP by a single whitespace character ' '.

@XmlElement(required=true)
@XmlJavaTypeAdapter(CollapsedStringAdapter.class)
String name;