Set the Http status code if it is not set

Question

I am trying to build a JSON string as server response with the aid of the Jackson library. If the route is not 0 I am getting tis response {"status":201,"routes":null} but I have problem to set the status variable to 204 in the SDBean class if the routeD is 0 I am getting in the console this output {"status":204,"routes":[1,9,3]} but in POSTMAN chrome extension the respose takes too long and I am getting this output The response status was 0. Check out the W3C XMLHttpRequest Level 2 spec for more details about when this happens. I want to get the following if routeD is not 0 to get {"status":201} else {"routes": {1,3,9}}

How can I manage that with Jakson?

Receiver class:

@Path("/data")
public class Receiver {

    @POST
    @Consumes(MediaType.APPLICATION_JSON)
    public Response storeData(Data data) {
        Database db = new Database();

        String macD = data.getMac();
        int routeD = data.getRoute();
        double latD = data.getLatitude();
        double longD = data.getLongitude();
        double speedD = data.getSpeed();

        SDBean bean = new SDBean();
        if (routeD != 0) {
            bean.status = db.insertData(macD, routeD, latD, longD);
            return Response.status(bean.status).entity(bean.toJson()).build();

        } else {
            bean.routes = db.detectRoute(latD, longD);
            return Response.status(bean.status).entity(bean.toJson()).build();

        }

    }

}

SDBean class:

import java.util.ArrayList;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class SDBean {

    public int status;
    public ArrayList<Integer> routes;

    public String toJson() {

        ObjectMapper mapper = new ObjectMapper();
        String json = null;

        if(status == 0){
            this.status = 204;
        }

        try {
            json = mapper.writeValueAsString(this);
        } catch (JsonProcessingException e) {
            e.printStackTrace();

        }
        return json;
    }

}

Answer 1

Your problem with 0 response due to you don't initialize your int value inside bean. When you try to analize your code :

//Inside Receiver 
return Response.status(bean.status).entity(bean.toJson()).build();

In this line you first get value from status field from bean. It's initialize with default value of 0 (Oracle documentation about primitive data types and default values) and next you map it toJson() where you set it's value to status response 204 in this line :

//Inside SDBean
if(status == 0){
    this.status = 204;
}

I suggest one of this resulutions:

1. Initialize variable inline:

   public int status = 204;

2. If you need some additional logic you could use static initialization block

   static {
       //additional logic here
       status = 204;
   }
   

3. Or simply use constructor in your case:

   public SDBean(){
       //additional logic here
       status = 204;
   }
   

For more info here you have documentation: Initializing fields.

Also you don't add anything to your ArrayList. Try to initialize it inside your bean inline:

public ArrayList<Integer> routes = new ArrayList<Integer>();

or if you use jdk 1.7+ use diamond interfece instead

public ArrayList<Integer> routes = new ArrayList<>();

And now you can use it to add your data inside storeData class:

bean.routes.add(yourIntValue);

// EDIT:

package com.gmail.at.mironiuk.kacper.stack.overflow.wtf;

import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

@Path("/data")
public class Receiver {

    @POST
    @Consumes(MediaType.APPLICATION_JSON)
    public Response storeData(Data data) {
        Database db = new Database();
        SDBean bean = new SDBean();

        String macD = data.getMac();
        int routeD = data.getRoute();
        double latD = data.getLatitude();
        double longD = data.getLongitude();
        double speedD = data.getSpeed();

        if (routeD != 0) { // here you always will have null or empty case you only set your status here
            bean.status = db.insertData(macD, routeD, latD, longD); // In this if try to add sth to your list
            bean.status = 204;
            return Response.status(bean.status).entity(bean.toJson()).build(); //Expected result {"status":"204", "routes": []}
        } else { // here your List will be this whats you returns from
            bean.routes = db.detectRoute(latD, longD); // <- this function and i don't know what function returns
            return Response.status(bean.status).entity(bean.toJson()).build(); //Expected result {"status":"204", "routes": [?,?,?]}
        }
    }

}

I hope that I help you