The implementation can determine the result based on the actual request
or the data of the parsed page. Typically this would call getNamedDecorator()
which would delegate to a parent DecoratorMapper.
Initialize the mapper. This is always called before the other methods.
Parameters: config - Config supplied by Servlet or Filter. Parameters: properties - Any initialization properties (specific to implementation). exception: java.lang.InstantiationException - should be thrown if the implementationcannot be initialized properly.