Cannot init the @FormBean field type as List<Integer> or Integer[]

Question

import javax.ws.rs.FormParam; import com.alibaba.fastjson.JSON;

Hi guys, The JAX-RS seems cannot init the list field in resteasy 2.x/3.x/4.x automatically,

Here is my VO used in servce

public class OrderVO {  
    @FormParam("id")
    private long id;    
    @FormParam("title")
    private String title;   
    @FormParam("product")
    private List<Integer> product;

    ...
    
    public String toString() {
        return JSON.toJSONString(this);
    }
}

And here is my service method:

@POST
@Consumes(MediaType.APPLICATION_FORM_URLENCODED+";charset=UTF-8")
@Path("/create")
public InsertResult saveOrder(@BeanParam OrderVO order) {
    logger.debug(order.toString());
    
}

Other parameters are auto inited except the List or Integer[], and can anyone tell me why....