Eclipse with Papyrus OCL based JAVA code generation

Question

I have created UML Class Diagram using Eclipse and Papyrus plugin.

In separate file I have defined OCL constraints

import 'model.uml'

package Shop

    context Product

    inv PriceIsNotNegative:
    self.price > 0

endpackage

I am trying to generate JAVA classes (left click > Designer > Generate Java Classes), but recently generated JAVA classes doesn't contain any sign of defined constraints. Where could be the problem?