JSON and Generics in Java - Type safety warning

Question

I have some data stored in Java elements and I need to return it in a given format - JSONObject. While my implementation works fine, I\'m still getting a warning message fro

Answer 1

You could create a map object and then do an explicit cast to JSONObject

Map<String, String> obj =  new HashMap<String, String>();
obj.put("id",way.getId());
JSONObject jsonObj =  (JSONObject) obj;

But note that this will restrict you only include "Strings" in your JSON. and you will see compile errors if you put another data structure. Say an array.

Answer 2

What is your JSONObject, does it inherit from HashMap? If does, the warn probably means that your should declare the JSONObject instance as follows:

JSONObject<String,Object> obj=new JSONObject<String,Object>();

Updated: Look at the definition of the JSONObject:

public class JSONObject extends HashMap

it extends HashMap but doesn't support parameter type, if its definition is

public class JSONObject<K,V> extends HashMap<K,V>

then we could write

JSONObject<String,Object> obj=new JSONObject<String,Object>();

and the put method will no longer generate the warning

Answer 3

public class JSONObject extends HashMap implements Map, JSONAware, JSONStreamAware

But does not have type parameter in class definition, The only option you have is to add the @SuppressWarnings("unchecked")

Answer 4

try to change the put line to other

 JsonPath.parse(jsonObj).set(fieldPath, Value);

Answer 5

FYI org.codehaus.jettison.json.JSONObject will not cause this warning. When using codehaus' JSONObject, you also have the ability to catch parsing errors via org.codehaus.jettison.json.JSONException. See https://github.com/codehaus/jettison for details.

Answer 6

Another option is to initialize the JSONObject with a (parameterized) Map<String, Object>. That way, a value can be of any valid JSON type, and you avoid the unchecked warning. E.g.:

public class WayToJsonConverter{
    ...
    public JSONObject wayToJson(){
        Map<String, Object> forJsonObj = new HashMap<>();
        forJsonObj.put("id",way.getId());  // No warning, hurray!
        forJsonObj.put("integer", 14);
        forJsonObj.put("floating", 1.4);
        JSONObject obj = new JSONObject(forJsonObj);
        ...
        return obj;
    }
    ...
}