JSON解析未使用Gson提供正确的值

Question

Hi I tried to parse a JSON like:

{"error":{"code":20,"message":"Transaction not found."}}

The Code is used is :

GulfBoxError errordetails= new Gson().fromJson(json, GulfBoxError.class);
                System.out.println("RESULT   :"+errordetails.getCode()+"   "+errordetails.getMessage());

Class file is:

public class GulfBoxError {
public int code;
public String message;

public int getCode() {
    return code;
}
public String getMessage() {
    return message;
}
}

Every time i tries and i didn't get he value here:

RESULT   :0   null

Any Idea Why?? What i am missing here

Answer 1

• You don't need getters if you don't encapsulate fields.
• You object is mailformed. Top level should contain only one field: error .

The code should look like:

public class GufError{
    public GulfBoxError error;
}

public class GulfBoxError {
    public int code;
    public String message;

    public int getCode() {
        return code;
    }

    public String getMessage() {
        return message;
    }
}

GufError errordetails= new Gson().fromJson(json, GufError.class);

Answer 2

You can try this, In case you don't want to create a separate class as wrapper:

Gson gson = new Gson();
JsonObject jsonObj = gson.fromJson(json,JsonObject.class);
GulfBoxError errordetails= gson.fromJson(jsonObj.get("error"), GulfBoxError.class);
System.out.println("RESULT   :"+errordetails.getCode()+"   "+errordetails.getMessage());

Answer 3

Your GulfBoxError class isn't correct.

You need something like this:

 public class GulfError{
    public GulfBoxError error;
}

 class GulfBoxError {
    public int code;
    public String message;

    public int getCode() {
        return code;
    }

    public String getMessage() {
        return message;
    }
}

And parse it in this way:

    Gson gson = new Gson();
    String filename="/...Pathtoyour/json.json";
    JsonReader reader = new JsonReader(new FileReader(filename));
    GulfError errordetails= gson.fromJson(reader, GulfError.class);
    System.out.print("errordetails: " + gson.toJson(errordetails));

Anyway, if you want to use your GulfBoxError class, you could do this:

      Type listType = new TypeToken<Map<String, GulfBoxError>>(){}.getType();
      Map<String, GulfBoxError> mapGulfBoxError= gson.fromJson(reader,listType);
      for (Map.Entry<String, GulfBoxError> entry : mapGulfBoxError.entrySet())
      {
          System.out.println("Key: " + entry.getKey() + "\nValue:" + gson.toJson(entry.getValue()));

      }

Sometimes this could be useful if you don't want to create exactly the object that represent your Json.