How to convert Json String with dynamic fields to Object?

Use a Map!

I would do the following

public class WebObjectResponse {
     private Map<String, DataInfo> networks;
} 

public class DataInfo {
     private String id = null;
     private String name = null;
}

// later
Gson gson = new Gson();
String json = "{\"networks\": {\"tech11\": { \"id\": \"1\",\"name\": \"IDEN\" },  \"tech12\": { \"id\": \"2\", \"name\": \"EVDO_B\" }    }}";

WebObjectResponse response = gson.fromJson(json, WebObjectResponse .class);

For each object in json networks, a new entry will be added to the Map field of your class WebObjectResponse. You then reference them by techXX or iterate through the keyset.

Assuming a structure like this

{
  "networks": {
    "tech11": {
        "id": "1",
        "name": "IDEN"
    },
    "tech12": {
        "id": "2",
        "name": "EVDO_B"
    },
    "tech13": {
        "id": "3",
        "name": "WOHOO"
    }, ...
  }
}

We would need your class structure for more details.

As far as I am aware, I think you will need to have some mappings defined somewhere (I used xml's) and then try to match json with one of the mappings to create objects.

Google gson is good. I did it in Jackson

Also, converting objects should be trivial. But since you might have variable fields like tech11 and tech12 , you might want to store the "network" value as a string and then extract fields out of it when required.

Hope I could help.

Edit : Sotirious nails it.