Exception "javax.xml.bind.UnmarshalException: unexpected element ..." thrown when mapping XML to Java using JAXB

Issue

• We are using JAXB to map XML to Java objects in my application like the following:

String xml = ...
JAXBContext context = JAXBContext.newInstance("com.example.app.model");
Unmarshaller unmarshaller = context.createUnmarshaller();
unmarshaller.unmarshal(IOUtils.toInputStream(xml, "UTF-8"));

• However, we get the following "javax.xml.bind.UnmarshalException: unexpected element ..." exception:

Caused by: javax.xml.bind.UnmarshalException: unexpected element (uri:"http://model.app.example.com", local:"MyData1"). Expected elements are <{}MyData1>,<{}MyData2>,<{}MyData3>[, ...]
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext.handleEvent(UnmarshallingContext.java:642)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:254)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportError(Loader.java:249)
    at com.sun.xml.bind.v2.runtime.unmarshaller.Loader.reportUnexpectedChildElement(Loader.java:116)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext$DefaultRootLoader.childElement(UnmarshallingContext.java:1049)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext._startElement(UnmarshallingContext.java:478)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallingContext.startElement(UnmarshallingContext.java:459)
    at com.sun.xml.bind.v2.runtime.unmarshaller.InterningXmlVisitor.startElement(InterningXmlVisitor.java:71)
    at com.sun.xml.bind.v2.runtime.unmarshaller.SAXConnector.startElement(SAXConnector.java:148)
    at com.sun.xml.bind.unmarshaller.DOMScanner.visit(DOMScanner.java:239)
    at com.sun.xml.bind.unmarshaller.DOMScanner.scan(DOMScanner.java:122)
    at com.sun.xml.bind.unmarshaller.DOMScanner.scan(DOMScanner.java:105)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:317)
    at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:297)
    at com.example.app.actions.MyAction.process(MyAction.java:106)
    ... 14 more