Why are people continuing to use xml mapping files instead of annotations? [closed]

Answer 1

• Lack of overview of what's been mapped. You need to dig in the source code.

Answer 2

The domain layer and the persistence layer are considered by some to be separate concerns. Using the pure XML approach keeps the two layers as loosely coupled as possible; using annotations couples the two layers more tightly as you have persistence-related code embedded in the domain code.

Answer 3

Using XML to complement the annotations, where environment or system specific configuration is needed.

Answer 4

people don't know that annotations are a full-featured replacement of xml mapping.

Ah, but they're not. Three cases off the top of my head (there are probably more) you can't do (well) with annotations:

1. Use formula as part of association key (admittedly, rather esoteric).
2. Join-via-subselect - @Loader is not an adequate replacement. Not too common but quite useful. Envers provides a viable alternate approach.
3. Losing column order for schema generation. This one's an absolute killer. I understand why it's done this way, but it still annoys me to no end.

Don't get me wrong, though - annotations are great; doubly so when they're coupled with Validator (though, again, #3 above kills the buzz on this one). They also provide certain aspects of functionality that XML mappings do not.

Answer 5

I worked on a project where the database would change very frequently and we have to regenerate the java files and configuration files each time it happens. Actually we do not use all the relationships and configurations generated by hibernate tool. So basically we use the tool and then modify/tweak them.

So when you want to modify/tweak the default configurations, it is easier to do in the XML file in comparison to doing it through annotations.

Answer 6

Some information is carried nicely in annotations, such as the cardinality of relationships between entities. These annotations provide more detail about the model itself, rather than how the model relates to something else.

However, bindings, whether to a persistence store or XML or anything else, are extrinsic to the model. They change depending on the context in which the model is used. Including them in the model is as bad as using inline style definitions in HTML. I use external binding (usually—though not necessarily—XML) documents for the same reasons I reference an external CSS.