Igor Kromin |   Consultant. Coder. Blogger. Tinkerer. Gamer.

I've recently had a requirement to unmarshal an XML fragment that was passed into one of my services. This in itself is typically not and issue and I've written code that does that plenty a time, however in this case I was having to unmarshal a fragment for a complex type, not for an element. That's where it got a little bit more complicated.

Initially my code was throwing the following exception:
javax.xml.bind.UnmarshalException: unexpected element (uri:"http://net.igorkromin/", local:"MyComplexType"). Expected elements are (none)

So that meant that the unmarshaller didn't recognise any valid elements in my XML string that I was trying to unmarshal. I checked the JAXB Context and it definitely had the complex type I was after so it was something else I was doing wrong.

Lets take a step back and look at the schema, my complex type, MyComplexType, was defined as:
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<xsd:schema xmlns="http://net.igorkromin/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" targetNamespace="http://net.igorkromin/" elementFormDefault="qualified">
<xsd:complexType name="MyComplexType">

That resulted in a JAXB generated class that looked like:
 Java Class
name = "MyComplexType",
propOrder = {...}
public class MyComplexType {

So, no XmlRootElement annotation. That's because it was a complex type and not an element of that type. That should have been obvious right away, but I missed it initially. Luckily there was a simple way around it. All I had to do was tell JAXB what complex type I was expecting and wrap the XML fragment as a Source or specifically StreamSource.

So the code that would achieve that looked something like...
String xmlString =
"< MyComplexType xmlns=\"http://net.igorkromin/\">\n" +
" ..." +
"</MyComplexType >";
JAXBContext ctx = JAXBContext.newInstance(MyComplexType.class);
Unmarshaller u = ctx.createUnmarshaller();
ByteArrayInputStream bais = new ByteArrayInputStream(xmlString.getBytes());
Source source = new StreamSource(bais);
JAXBElement<MyComplexType> mct = u.unmarshal(source, MyComplexType.class);

That worked like a charm and I could then get my unmarshalled complex type instance from the JAXBElement instance.


Hope you found this post useful...

...so please read on! I love writing articles that provide beneficial information, tips and examples to my readers. All information on my blog is provided free of charge and I encourage you to share it as you wish. There is a small favour I ask in return however - engage in comments below, provide feedback, and if you see mistakes let me know.

If you want to show additional support and help me pay for web hosting and domain name registration, donations, no matter how small, are always welcome!

Use of any information contained in this blog post/article is subject to this disclaimer.
comments powered by Disqus
Other posts you may like...