TIL: JAXB Marshallers and Unmarshallers are not thread-safe

If you’re using JAXB in Java, be careful because Marshaller and Unmarshaller instances are not thread-safe. The JAXBContext is, however.

That means you shouldn’t reuse them across threads without some kind of synchronization. I ended up fixing this by using ThreadLocal.

I found this today while debugging a weird serialization issue. One of those bugs that only shows up under load…