@Entity
public class User {
    private Long id;

    private int age;

    @Id
    public Long getId() {
        return id;
    }

    public void setId(T id) {
        this.id = id;
    }

    @Min(0)
    @Max(150)
    @Column(nullable = false)
    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

org.hibernate.jpamodelgen.annotation.MetaAttributeGenerationVisitor
public AnnotationMetaAttribute visitPrimitive(PrimitiveType t, Element element) {
    //TypeUtils.toTypeString( t ) will be return null
    return new AnnotationMetaSingleAttribute( entity, element, TypeUtils.toTypeString( t ) );
}

org.hibernate.jpamodelgen.util.TypeUtils
public static String toTypeString(TypeMirror type) {
    if ( type.getKind().isPrimitive() ) {
        //type.toString() will be return @javax.validation.constraints.Min(0L),@javax.validation.constraints.Max(150L) int
        return PRIMITIVES.get( type.toString() ); //throw NullPointException
    }
    return type.toString();
}