Unable to use the default hashmap constructor for groovy classes

Unable to use the default hashmap constructor (Syntaxt : new Person(name:"Martin", firstName:"John") ).

This script show differrent result in groovy (JSR-06) from XWiki.
The script:

class Person

{ def Personne(pName, pFN, pAge, pFeet, pOld) { name = pName firstname = pFN age = pAge old = pOld }

String name
String firstname
int age
int feet
int old
}

mytable=[new Person(name:"Georges",firstname:"Arthur",age:34,feet:2,old:4),
new Person(name:"Schputz",firstname:"Lolo",age:32,feet:2,old:4),
new Person(name:"Moran",firstname:"Marcel",age:11,feet:3,old:5),
new Person(name:"Flutor",firstname:"Jacques",age:23,feet:2,old:8)];

println mytable.size() //
for ( myi in mytable)
{
println myi.firstname
}

Result in grooyv
4
Arthur
Lolo
Marcel
Jacques

Result in XWiki
4 null null null null

I can get around by using an explicit constructor, but its quite verbose.