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POJAXB throwing InstantiationException trying to marshal xsi:type based on abstract class
 

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    <p>I am having an issue with using inheritance and JAXB unmarshalling. I have read the number of examples (specifically a much-reference blog at <a href="http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-xsitype.html" rel="nofollow noreferrer">http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-xsitype.html</a> and a very similar SO question here: <a href="https://stackoverflow.com/questions/11219074/jaxb-xsitype-subclass-unmarshalling-not-working">JAXB xsi:type subclass unmarshalling not working</a>) and am still having difficulties.</p> <p>Like many of these other questions, I am trying to create an XML representation of an object whose fields rely on subclasses for information. I do not know at compile time what the concrete subclass implementation will be, so things like XmlSeeAlso is not really available. </p> <p>In my test case I have a Root class with an abstract class (A) that has a concrete subtype (B):</p> <pre><code>@XmlRootElement @ToString public class Root { private A theClass; public A getTheClass() { return theClass; } public void setTheClass(A theClass) { this.theClass = theClass; } } @ToString public abstract class A { } @XmlRootElement @ToString public class B extends A { private String b = "from B-" + System.currentTimeMillis() public String getB() { return b; } public void setB(String b) { this.b = b; } } </code></pre> <p>Where @ToString are annotations from project Lombok.</p> <p>I can marshall with no problem:</p> <pre><code>@Test public void marshallTest() { try { Root r = new Root(); B b = new B(); r.setTheClass(b); Class&lt;?&gt;[] classArray = new Class&lt;?&gt; [] { Root.class, B.class }; JAXBContext context = JAXBContext.newInstance(classArray); Marshaller marshaller = context.createMarshaller(); try (FileWriter fw = new FileWriter(JAXB_TEST_XML)) { marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); marshaller.marshal(r, fw); } try(StringWriter sw = new StringWriter() ) { marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); marshaller.marshal(r, sw); log.debug("{}", sw.toString()); } } catch (IOException | JAXBException e) { e.printStackTrace(); fail(e.getMessage()); } } </code></pre> <p>Which produces the following xml:</p> <pre><code>&lt;root&gt; &lt;theClass xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="b"&gt; &lt;b&gt;from B-1375211003868&lt;/b&gt; &lt;/theClass&gt; &lt;/root&gt; </code></pre> <p>When I try to unmarshall (using MOXY JAXB implemntation) I get: </p> <pre><code>This class does not define a public default constructor, or the constructor raised an exception. Internal Exception: java.lang.InstantiationException Descriptor: XMLDescriptor(xml.A --&gt; []) </code></pre> <p>With the following code:</p> <pre><code>@Test public void unmarshall() { try { JAXBContext context = JAXBContext.newInstance(new Class&lt;?&gt;[] {Root.class, A.class}); DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance(); documentBuilderFactory.setNamespaceAware(true); DocumentBuilder db = documentBuilderFactory.newDocumentBuilder(); Root r = null; try(BufferedInputStream bis = new BufferedInputStream(new FileInputStream(JAXB_TEST_XML))) { Document doc = db.parse(bis); Unmarshaller unmarshaller = context.createUnmarshaller(); JAXBElement&lt;?&gt; result = unmarshaller.unmarshal(doc, Root.class); r = (Root) result.getValue(); } assertTrue(r != null &amp; r.getTheClass() != null &amp;&amp; r.getTheClass() instanceof B); } catch (Exception e) { e.printStackTrace(); fail(e.getMessage()); } } </code></pre> <p>I have tried making the unmarshalling namespace aware (as with <a href="https://stackoverflow.com/questions/11219074/jaxb-xsitype-subclass-unmarshalling-not-working)a">JAXB xsi:type subclass unmarshalling not working</a> which has not worked. I have tried using XmlElementRef which does not work either. I have tried the latest glassfish api and implementations downloaded from maven central (2.2.8). I have tried the MOXY eclipse persistence JAXB implementation. Neither have worked. I have tried unmarshalling without using a document builder which does not work as well. I have tried passing the Root.class and A.class into the JAXB context which also does not work. </p> <p>I have a feeling that I have a fundamental misconception about what is going on. Any hints or ideas would be appreciated. Thank you.</p> <ul> <li>Chooks</li> </ul>
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