Unit testing JAXB marshalling and XJC-generated classes

JAXB – the Java Architecture for Xml Binding provides a simple way of mapping XML to POJOs. It give the ability of painlessly marshalling and unmarshalling objects to and from XML.

JAXB’s usefulness is enhanced by the ‘xjc’ tool that is included in the SDK, which converts an XML schema to a set of Java classes.

A portion of the XML schema (which itself is generated from an XML file):

  <xs:complexType name="MetaType">
      <xs:attribute type="xs:string" name="Name" use="optional"/>
      <xs:attribute type="xs:string" name="Scheme" use="optional"/>
      <xs:attribute type="xs:string" name="Value" use="optional"/>
  </xs:complexType>

Because the XML schema I’m working with has been auto-generated from sample XMLs and not hand-written (and fairly complex!), I’d like to ensure that the XML coming out of the marshalling is what I expect.

The following JUnit 4 test creates and populates the object, then verifies that the object is marshalled to XML properly:

public class MetaTypeTest {
    private final String _xmlHeader = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>";

    @Test
    public void shouldMarshalAllAttributes() throws Exception {
        final MetaType type = new MetaType();
        type.setName("MetaName");
        type.setScheme("MetaScheme");
        type.setValue("MetaValue");

        // Can't be certain @XmlRootElement annotation has been generated, so wrap obj in JAXBElement
        final JAXBElement element = new JAXBElement(new QName("Meta"), MetaType.class, type);

        // Marshal to output stream
        JAXBContext context = JAXBContext.newInstance(MetaType.class);
        final ByteArrayOutputStream outStream = new ByteArrayOutputStream();
        context.createMarshaller().marshal(element, outStream);

        final String xmlContent = "";
        Assert.assertEquals(_xmlHeader + xmlContent, outStream.toString());
    }
}

More..

• Wikipedia
• Unofficial JAXB guide (Hosted on glassfish’s dev.java.net)
• Sample XJC binding guide