使用GSON从DistanceMatrix Google Api将嵌套数组Json解析为Java

Question

I need to parsing Json in Java object and save the fields: destination_addresses, origin_addresses and duration. I can not get the values of "duration". This is the json which I have to parse:

{
   "destination_addresses" : [ "Blocco Palma Primo, 95121 Fattoria Sole Delfino CT, Italia" ],
   "origin_addresses" : [
      "Unnamed Road, 95121 Catania CT, Italia",
      "Blocco Palma Primo, 95121 Fattoria Sole Delfino CT, Italia",
      "Contrada Torre Allegra, 95121 Catania CT, Italia",
      "Contrada Pantano d'Arci, Catania CT, Italia",
      "Unnamed Road, 95121 Catania CT, Italia",
      "Via Cassia, 95121 Catania CT, Italia",
      "Contrada Pantano d'Arci, Catania CT, Italia",
      "Contrada Pantano d'Arci, Catania CT, Italia",
      "Contrada Pantano d'Arci, Catania CT, Italia",
      "Contrada Pantano d'Arci, Catania CT, Italia"
   ],
   "rows" : [
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "2,0 km",
                  "value" : 2037
               },
               "duration" : {
                  "text" : "4 min",
                  "value" : 266
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "1 m",
                  "value" : 0
               },
               "duration" : {
                  "text" : "1 min",
                  "value" : 0
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "3,8 km",
                  "value" : 3768
               },
               "duration" : {
                  "text" : "7 min",
                  "value" : 400
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "5,3 km",
                  "value" : 5304
               },
               "duration" : {
                  "text" : "6 min",
                  "value" : 374
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "8,2 km",
                  "value" : 8239
               },
               "duration" : {
                  "text" : "13 min",
                  "value" : 785
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "11,5 km",
                  "value" : 11486
               },
               "duration" : {
                  "text" : "15 min",
                  "value" : 901
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "12,2 km",
                  "value" : 12226
               },
               "duration" : {
                  "text" : "18 min",
                  "value" : 1099
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "12,2 km",
                  "value" : 12226
               },
               "duration" : {
                  "text" : "18 min",
                  "value" : 1099
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "12,2 km",
                  "value" : 12226
               },
               "duration" : {
                  "text" : "18 min",
                  "value" : 1099
               },
               "status" : "OK"
            }
         ]
      },
      {
         "elements" : [
            {
               "distance" : {
                  "text" : "12,2 km",
                  "value" : 12226
               },
               "duration" : {
                  "text" : "18 min",
                  "value" : 1099
               },
               "status" : "OK"
            }
         ]
      }
   ],
   "status" : "OK"
}

And this is what I tried in Java, to get the fields that I need:

public static void main(String[] args) throws Exception {
        // TODO code application logic here
        URL url = new URL(myUrl);
        InputStreamReader reader = new InputStreamReader(url.openStream());
        SRD sr = new Gson().fromJson(reader, SRD.class);

        System.out.println("destination: " + sr.destination_addresses.get(0));
        System.out.println("origins: " + sr.origin_addresses.get(2));
        System.out.println(sr.rows.get(2).elements.get(0).toString());



    }

With these classes:

private class SRD {
        List<String> destination_addresses;
        List<String> origin_addresses;
        List<elements> rows;

    }


    private class elements {
        List<duration> elements;

    }

    private class duration {
        String text;
        int value;


        public String toString() {
            return "duration{" + "text=" + text + ", value=" + value + '}';
        }


    }

Executing this code I get the following output:

destination: Blocco Palma Primo, 95121 Fattoria Sole Delfino CT, Italy

origins: Contrada Torre Allegra, 95121 Catania CT, Italy

duration{text=null, value=0}

Obviously, I can successfully do the parsing of fields destination_addresses and origin_addresses, but not the duration, of which gives me values 0 and null. Where am I wrong? How can I solve this problem and get the correct values (text and value) of duration? Thank for your help.

Answer 1

Here, In java class names should start with uppercase.

If it is problem to access objects just define getter methods.

I didn't make seperate classes of duration and distance objects because of that they are both have same type and name properties.

private class SRD {
    List<String> destination_addresses;
    List<String> origin_addresses;
    List<Row> rows;

}

private class Row{
    List<Element> elements;

}


private class Element {
    General duration;
    General distance;
    String status; 

}

private class General {
    String text;
    int value;


    public String toString() {
        return "duration{" + "text=" + text + ", value=" + value + '}';
    }


}