Question

I have the following Item class:

public class Item {
    public Object item;
}

I am inserting a JSON into this object using GSON.

tmp =

{
    "_id": {
        "$oid": "5076371389d22e8906000000"
    },
    "item": {
        "values": [
            {
                "value1": [
                    4958,
                    3787,
                    344
                ],
                "value2": [
                    4,
                    13,
                    23
                ]
            }
        ], 
        "name": "item1"
    }
}

Java bit:

Item item = new Item();
Gson g = new Gson();
it = g.fromJson(tmp.toString(), Item.class);

it.item becomes a StringMap type (http://code.google.com/p/google-gson/source/browse/trunk/gson/src/main/java/com/google/gson/internal/StringMap.java?r=1131)

I now need to access the sub-objects within this object.
I can use the overridden toString function this type has which prints all objects within this object. But how would I be able to navigate through it?
P.S. The reason I put everything into an object datatype not a structured class is that the JSON structure varies each time, so I can’t really have a class schema.
Any suggestions?

Answer 1

You should create an object structure that reflects the JSON instead (since this is what you’re trying to do anyway). For your example, you could use this:

public class MyObject {
    private Item item;
    private String _id;

    // getters, setters, etc.
}

public class Item {
    private List<Value> values;
    private String name;

    // getters, setters, etc.
}

public class Value {
    private List<Integer> values1;
    private List<Integer> values2;

    // getters, setters, etc.
}

Then pass MyObject.class to Gson:

MyObject myObj = g.fromJson(tmp.toString(), MyObject.class);

You can get the lists in values like so:

List<Integer> values1 = myObj.getItem().getValues().get(0).getValues1();
List<Integer> values2 = myObj.getItem().getValues().get(0).getValues2();

Try that and see if it works.

Also, you should check out my answer to a similar question here, specifically the part at the end about how to write an object structure for Gson based on some JSON object.