XML to POJO and back. Horses for courses.

One aspect I've looked at in the recent past was the ability to turn POJOs into XML back into POJOs. There are a myriad of utilities out there to do just that. JAXB, Javolution, XMLBeans, XStream, JiBX and many more. Granted, some of the utilities are way smarter than others and offer different levels of functionality. With some you have to write code in your POJO. Others work of XML Schemas, you feed some sort of compiler a schema and it spits out POJOa galore which you then access using factories and such.

Of the utilities I've mentioned before JAXB and XMLBeans are a notable example of the XML Schema to POJO route. I feed a compiler a schema and it spits out POJOs. So if you are given a schema, go fry your brains with one of these tools. Real easy. Because you work from the schema to a Java representation the content and format of the Java classes created from the schema are out of your hands. It means that if you get an ugly, badly designed schema, you'll end up with ugly, non-intuitive Java. In that case you might have to use a second round of transformations like dozering or hand-written Java to Java transformation. You also have to write schema-centric or XML-centric application code. You are constantly remided that there is a document at stake somewhere. Now what can I say about JAXB and XMLBeans - "XML Schema to Java in 60 seconds" I guess...

Jovolution is somewhat different from the other utilities in that it is part of a high-performance, realtime Java library. So you write your Java code first. You can then add your Java to XML serialization and XML to Java deserialization code. It allows you to produce XML that are more element centric or more attribute centric - depending on your mood or your boss' mood. It is relatively easy to use once you've figured it out. Fortunately there is an eclipse plug-in that makes your life a whole lot easier - that is if you use eclipse of course (why wouldn't you). Don't use Javolution if you have a schema somewhere that the XML needs to adhere to, you'll get depressed and stressed and might suffer a nervous breakdown... What will be a nice catch phrase for Javolution - "kickass performance after you've figured it out". The figuring is the hard part...

If you have Java and want to go to XML you can also use XStream. Boy what a pleasure. Easy as pie. Five lines of code. Really, really easy. Did you get that, simple as sneeze! You do not have a great deal of power to configure what your XML will look like but hey, who cares, with this ease of use who wants to specify in great detail what the XML is produce should look like. Ok, so now we've covered the "extremes" if I may say so - schema driven XML to POJO or Java driven POJO to XML code.

JiBX allows you complete control over the mapping of XML to Java (or Java to XML). Its flexibility may come at a price. You can end up with XML and POJOs that at face value does not look the same. You will also have to work with a mapping compiler and such. From a Java point of view it is totally non-intrusive. Nowhere in your Java will you ever know about the underlying XML (except of course in your marshaler, unmarshaler service). It also has nice functionality like having binding specifications of different versions, so if you want to provide XML for Bob, use your Bob mapping and if you want to provide XML for Sue use your Sue mapping. Very nice. What can I say about JiBX - I guess "hard work, great rewards" sums it up best. Oh yeah, forget the schema - unless you want to use some of the tools supplied with JiBX...