How to force a JAXBException when marshalling for a JUnit test

Question

I haven't been able to find a way to force a JAXBException when marshalling for a JUnit test. Does anyone have any ideas?

Here is my marshalling code:

   public String toXml() {
          log.debug("Entered toXml method");
    String result = null;
    try {
        JAXBContext jaxbContext = JAXBContext.newInstance(Config.class);
        Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
        jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        StringWriter writer = new StringWriter();
        jaxbMarshaller.marshal(this, writer);
        result = writer.toString();
    } catch (JAXBException e) {
          log.error(e);
    }
          log.debug("Exiting toXml method");
    return result;
   }

Answer 1

There are different ways to create a JAXBException during a marshal operation:

1 - Marshal an Invalid Object

You can generate a JAXBException during a marshal operation by marshalling an instance of a class that the JAXBContext isn't aware of (i.e. Take your example and use it to marshal an instance of Foo). This will produce the following exception.

Exception in thread "main" javax.xml.bind.JAXBException: class forum13389277.Foo nor any of its super class is known to this context.
    at com.sun.xml.bind.v2.runtime.JAXBContextImpl.getBeanInfo(JAXBContextImpl.java:594)
    at com.sun.xml.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:482)
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:315)
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:244)
    at javax.xml.bind.helpers.AbstractMarshallerImpl.marshal(AbstractMarshallerImpl.java:95)
    at forum13272288.Demo.main(Demo.java:27)

2 - Marshal to Invalid Output

If you try to marshal to an invalid output such as an OutputStream that has been closed:

    FileOutputStream closedStream = new FileOutputStream("src/foo.xml");
    closedStream.close();
    jaxbMarshaller.marshal(this, closedStream);

Then you will get a MarshalException which is a subclass of JAXBException.

Exception in thread "main" javax.xml.bind.MarshalException
 - with linked exception:
[java.io.IOException: Stream Closed]
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:320)
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:244)
    at javax.xml.bind.helpers.AbstractMarshallerImpl.marshal(AbstractMarshallerImpl.java:95)
    at forum13272288.Demo.main(Demo.java:27)
Caused by: java.io.IOException: Stream Closed
    at java.io.FileOutputStream.writeBytes(Native Method)
    at java.io.FileOutputStream.write(FileOutputStream.java:318)
    at com.sun.xml.bind.v2.runtime.output.UTF8XmlOutput.flushBuffer(UTF8XmlOutput.java:413)
    at com.sun.xml.bind.v2.runtime.output.UTF8XmlOutput.endDocument(UTF8XmlOutput.java:137)
    at com.sun.xml.bind.v2.runtime.output.IndentingUTF8XmlOutput.endDocument(IndentingUTF8XmlOutput.java:165)
    at com.sun.xml.bind.v2.runtime.XMLSerializer.endDocument(XMLSerializer.java:852)
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.postwrite(MarshallerImpl.java:369)
    at com.sun.xml.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:316)
    ... 3 more