Question

I’ve a little problem with GSON-JSON.

Let see the following code:

    public static class ProtoQuery {
    public String action;
    public String token;
    public Object params;

    public ProtoQuery(String action, String token, Object params) {
        this.action = action;
        this.token = token;
        this.params = params;
    }
}


// Authentication Phase
public static class ProtoAuth {
    public String username;
    public String password;

    public ProtoAuth(String username, String password) {
        this.username = username;
        this.password = password;
    }
}


    // Serialize Object
    Gson gson = new Gson();
    ProtoQuery tmp = new ProtoQuery("ProtoAuth", "", new JirckeProtocol.ProtoAuth("ABC", "myPASS"));
    String json = gson.toJson(tmp);

    // Deserialize Object
    ProtoQuery deserializedOBJ = gson.fromJson(json, ProtoQuery.class);

Here the problem:
deserializedOBJ.object return a LinkedHashMap.
I want to convert back into ProtoAuth object..How I can know that is a ProtoAuth? Using the “action” params in ProtoQuery.

I need something like
deserializedOBJ.params = gson.fromJSON(json.object, ProtoAuth.class)

What’s the best way to do this?
There is an alternative to do this, without write my own serializer/deserialer?

Actually I use that code:

deserializedOBJ.params = gson.fromJson(element, Class.forName("MyProtocol$ProtoAuth"));

Answer 1

I would type ProtoQuery as following:

public static class ProtoQuery<T> {
    public String action;
    public String token;
    public T params;

    public ProtoQuery(String action, String token, T params) {
        this.action = action;
        this.token = token;
        this.params = params;
    }
}


// Authentication Phase
public static class ProtoAuth {
    public String username;
    public String password;

    public ProtoAuth(String username, String password) {
        this.username = username;
        this.password = password;
    }
}

and to deserialize with a param of type ProtoAuth, you can call as followed:

Type type = new TypeToken<ProtoQuery<ProtoAuth>>() {}.getType();
ProtoQuery<ProtoAuth> deserializedOBJ = gson.fromJson(json, type);