code: private AbstractConstraint<?> getConstraint(String constraintName) throws PropertyException{
  		String constraintString = props.getProperty(constraintName);
  		if(constraintString == null)
  			throw new PropertyException(ConstraintContextProperty.CONSTRAINT, constraintName, "Unparseable constraint");
  		AbstractConstraint<?> result = null;
  		try{
  			result = NumberConstraint.parse(constraintString);
  		}catch(Exception e){
  			try{
  				result = StringConstraint.parse(constraintString);
  			}catch(Exception e1){
  				throw new PropertyException(ConstraintContextProperty.CONSTRAINT, constraintName, "Unparseable constraint", e1);
  			}
  		}
  		return result;
  	}
docs: Extracts the constraint with the given name in form of a constraint-object.<br>
  @param constraintName The property-name of the constraint (CONSTRAINT_X)
  @return The constraint-representation of the constraint-property
  @throws PropertyException if there is no constraint with the given name or the value cannot be converted into a number- or string-constraint.