I want to know why you would use castor as a serialization framework when developing web services.
I understand that you can develop a web service without using an external serialization framework like castor. I would just like to know when it is recommended to use a external serialization framework like castor.
Nowadays we have JAXB, the standard Java API for XML binding. I would prefer to use that, just because it's the standard, instead of something like Castor. A few years ago JAXB didn't exist yet, so Castor was a good choice.
Especially if you use JAX-RS (Jersey) for RESTful webservices, JAXB is a great choice, because it understands JAXB annotations and makes it easy to create RESTful webservices - it can also serialize to JSON instead of XML, using the JAXB annotations.