public interface Wrapper
The Wrapper interface is one of the two ways a user can initialize a
Wrapper object.
By default, when schema2beans generates the java classes, a #PCDATA DTD type
is mapped to a java String. Sometime, the user might want to map an
element to either a scalar or a specialized type (user defined class).
For example, a price DTD element specified as #PCDATA could be mapped
to a float or integer data type. Or a date DTD element also specified
as #PCDATA could be mapped to a specialized Date object, that the user might
provide. schema2beans calls these specialized object 'wrappers'.
If the user specifies a wrapper object in the mdd file (see user
documentation for mdd explanations), schema2beans uses the wrapper class
instead of the String type. In this case, schema2beans needs to initialize
the wrapper object using the String value from the XML document, and
also needs to be able to get the String value from the wrapper
object (in order to write back the XML document).
This what this Wrapper interface provides. A wrapper class has
has either to have a String constructor and toString() method,
or implements the Wrapper interface. This is how schema2beans can set/get
the String values of user wrapper/customized object.