Elementos vacíos para los tipos de datos primitivos prohibidos en XSD

Question

Me encontré con un error de análisis con Apache CXF mientras se procesa una respuesta de servicio web.Lo que se trata de abajo es un elemento vacío que se devuelve:

<myValue />

La definición del elemento es la siguiente:

<xsd:element name="myValue" type="xsd:float" minOccurs="0">

Ahora he leído en la lista de correo CXF que una Valor vacíono está permitido por el XSD-SPET :

Bueno, no hay una solución para Esto, ya que no es un error.Un vacío El elemento no es válido para ningún decimal. o tipo de fecha o algo así.
Así, debería lanzar una excepción.
¿Qué esperas que haga?

AHORA Aquí viene la pregunta: ¿Dónde puedo encontrar exactamente esta restricción en la especificación de esquema XML?

Answer 1

Where exactly can I find this constraint in the XML Schema specification?

http://www.w3.org/TR/xmlschema-2/#float-lexical-representation

float values have a lexical representation consisting of a mantissa followed, optionally, by the character "E" or "e", followed by an exponent.
...
The representations for exponent and mantissa must follow the lexical rules for integer and decimal.
...
The special values positive and negative infinity and not-a-number have lexical representations INF, -INF and NaN, respectively.

So xs:float requires at least a mantissa that is a xs:decimal...

decimal has a lexical representation consisting of a finite-length sequence of decimal digits (#x30-#x39) separated by a period as a decimal indicator. An optional leading sign is allowed.

...and an empty string is not a valid xs:decimal.

If you don't have a value for this element, you should try not including this element, if possible. Your schema seems to allow omitting this element because minOccurs has value 0. Other solution would be to insert a suitable replacement value, like 0 or NaN.

Answer 2

This is not a definitive constraint. You should be able to change your xsd to

<xsd:element name="myValue" type="xsd:float" minOccurs="0" default="0" />

And then be able to supply an empty element for your float without causing your xml to be invalid.

The above example means that if the element is empty, then its value is 0. Beware, default attribute does not apply on missing elements: missing elements are just missing, whether they have a declared default or not. http://www.w3.org/TR/xmlschema-0/#OccurrenceConstraints

if the element appears without any content, the schema processor provides the element with a value equal to that of the default attribute. However, if the element does not appear in the instance document, the schema processor does not provide the element at all.

I have not used this till now, but to guard against a personal miss-reading of w3c specs, I have check with an online validator that an xml with an empty xs:float element having a default was accepted (at least by this online validator: http://www.freeformatter.com/xml-validator-xsd.html ).