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

Question

How to configure JAXB unmarshaller so it will trim leading and trailing whitespaces from strings?

For instance let's consider a simple binding between a Java bean and XML using JAXB annotations:

@XmlRootElement(name="bean")
class Bean {

  @XmlElement(required=true)
  String name;

  @XmlElement(required=true)
  int number;
}

I would like to be able to unmarshal XML given bellow so bean.name does not include starting and trailing whitespaces - is "My name", not "\n My name\n ".

<bean>
  <name>
    My name
  </name>
  <number>1</number>
</bean>

Answer 1

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;

Answer 2

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;