def initialize( list = {}, entity = nil )
@entity = entity
@allow_null = list['allow_null']
@name = list['name']
@class_name = list['class_name']
@column_name = list['column_name']
@external_type = list['external_type']
@value_type = list['value_type']
@width = list['width']
@precision = list['precision']
@read_only = list['read_only'] || false
@factory_method = list['factory_method']
@argument_type = list['argument_type']
@conversion_method = list['conversion_method']
@read_format = nil
@write_format = nil
if @allow_null.nil? then
@allow_null = false
end
end