This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff on-line! See this thread for details.
The "classic approach" is to create one or more XML schemas that describe the data your web service will send and receive.
Then one use the XJC JAXB schema compiler to generate the JAXB bean classes. The XJC schema compiler can be used from Maven or Ant, so it can be part of your build process.
Finally, the JAXB bean classes are used in the code either to interpret received XML or to prepare an object representation of response data, which is later marshalled into XML.
Ask for more details!