All properties in your mapping file must exist in your Java class, and all properties must have getter and setter methods so Hibernate can manipulate these values. So if you map a property "foo" which is of the type
String, your class must have a getter called getFoo() that returns a String and a setter called setFoo(String) that takes a string as a parameter. Associations are the same, if foo is an association to a class called Foo you'll need the same getter and setter methods that deal with Foo objects.