CODEWITHSUNDEEP
androidasp.netjsonjson.netgson
Abijeet Patro
Abijeet Patro

Reputation: 2884

List of user-defined objects from Android to an ASP.NET webservice through JSON

I have a web service written in ASP.NET that accepts a List of type Contact(List).

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    #region List of contacts that need to be created in the database.
    public List<KeyValue> createRecordsInDb(List<Contact> dataToPass)
    {
        return Contact.insertArrayIntoDb(dataToPass);
    } 
    #endregion

On the android device, I am converting a List to a String using the GSON library.

    List<Contact> lstContactsToCreate= retrieveDataFromCursor(cursor,false);
    String jsonString = new Gson().toJson(lstContactsToCreate);
    try {
        callWebService(jsonString, _context.getResources().getString(R.string.updateCreateURL), false);
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (NotFoundException e) {
        e.printStackTrace();
    } catch (JSONException e) {
        e.printStackTrace();
    } catch (IOException e) {           
        e.printStackTrace();
    }

The problem arises when I wish to send the data to the web-service. I'm passing the data through the following method,

private HttpResponse callWebService(String dataToPass, String URL, boolean isUpdate) 
        throws JSONException, ClientProtocolException, IOException{
    HttpPost httpPost = new HttpPost(URL);
    httpPost.setHeader("content-type", "application/json");

    HttpClient httpClient = new DefaultHttpClient(getHttpParameterObj(4000,4000));

    // Building the JSON object.
    JSONObject data = new JSONObject();
    data.put("dataToPass", dataToPass);

    StringEntity entity = new StringEntity(data.toString(), HTTP.UTF_8);

    entity.setContentType("application/json");
    entity.setContentEncoding( "UTF-8");

    httpPost.setEntity(entity);
    // Making the call.
    HttpResponse response = httpClient.execute(httpPost);
    return response;
}

Whenever I call the webservice, it throws the following error - 

{"Message":"Cannot convert object of type \u0027System.String\u0027 to type \u0027System.Collections.Generic.List`1

The problem is that data.toString() returns :-

{"dataToPass":"[{\"address\":\"Himayath Nagar\",\"email\":\"[email protected]\",\"name\":\"Abijeet Patro\",\"server_id\":\"\",\"status\":\"\"},{\"address\":\"himayath naga\",\"email\":\"[email protected]\",\"name\":\"Saravana\",\"server_id\":\"\",\"status\":\"\"},{\"address\":\"hellpo world\",\"email\":\"[email protected]\",\"name\":\"Syai\",\"server_id\":\"\",\"status\":\"\"}]"}

whereas the webservice expects data in the format

{"dataToPass":[{\"address\":\"Himayath Nagar\",\"email\":\"[email protected]\",\"name\":\"Abijeet Patro\",\"server_id\":\"\",\"status\":\"\"},{\"address\":\"himayath naga\",\"email\":\"[email protected]\",\"name\":\"Saravana\",\"server_id\":\"\",\"status\":\"\"},{\"address\":\"hellpo world\",\"email\":\"[email protected]\",\"name\":\"Syai\",\"server_id\":\"\",\"status\":\"\"}]}

I even tried replacing and removing those " " as such :- 

data.toString().replace("\"[","[").replace("]\"","]");
     (java.lang.String) {"dataToPass":[{\"address\":\"Himayath Nagar\",\"email\":\"[email protected]\",\"name\":\"Abijeet Patro\",\"server_id\":\"\",\"status\":\"\"},{\"address\":\"himayath naga\",\"email\":\"[email protected]\",\"name\":\"Saravana\",\"server_id\":\"\",\"status\":\"\"},{\"address\":\"hellpo world\",\"email\":\"[email protected]\",\"name\":\"Syai\",\"server_id\":\"\",\"status\":\"\"}]}

But that does not seem to be working as the Web Server throws an error

{"Message":"Invalid object passed in, member name expected. (16): {\"dataToPass\":[{\\\"address\\\":\\\"Himayath Nagar\\\",\\\"email\\\":\\\"[email protected]\\\",\\\"name\\\":\\\"Abijeet Patro\\\",\\\"server_id\\\":\\\"\\\",\\\"status\\\":\\\"\\\"},{\\\"address\\\":\\\"himayath naga\\\",\\\"email\\\":\\\"[email protected]\\\",\\\"name\\\":\\\"Saravana\\\",\\\"server_id\\\":\\\"\\\",\\\"status\\\":\\\"\\\"},{\\\"address\\\":\\\"hellpo world\\\",\\\"email\\\":\\\"[email protected]\\\",\\\"name\\\":\\\"Syai\\\",\\\"server_id\\\":\\\"\\\",\\\"status\\\":\\\"\\\"}]}","StackTrace":"   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeDictionary(Int32 depth)\r\n   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth)\r\n   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeList(Int32 depth)\r\n   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth)\r\n   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeDictionary(Int32 depth)\r\n   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth)\r\n   at System.Web.Script.Serialization.JavaScriptObjectDeserializer.BasicDeserialize(String input, Int32 depthLimit, JavaScriptSerializer serializer)\r\n   at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit)\r\n   at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize[T](String input)\r\n   at System.Web.Script.Services.RestHandler.GetRawParamsFromPostRequest(HttpContext context, JavaScriptSerializer serializer)\r\n   at System.Web.Script.Services.RestHandler.GetRawParams(WebServiceMethodData methodData, HttpContext context)\r\n   at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.ArgumentException"}

So how do I pass an array of user-defined objects from Java to my ASP.NET web service? Or is there way I can convert the GSON string on the asp.net web server to my List objects?

Can I use JSON.NET to de-serialize the string to my List?

Upvotes: 1

Views: 729

Answers (1)

Abijeet Patro
Abijeet Patro

Reputation: 2884

This link has an answer that worked. I am just getting the data on the server side as string, and then converting it the array that I can process.

Sample JSON:

string json = "[{Name:'John Simith',Age:35},{Name:'Pablo Perez',Age:34}]";

Class:

public class Person
{
 public int Age {get;set;}
 public string Name {get;set;}
}

Deserialization

JavaScriptSerializer js = new JavaScriptSerializer();
Person [] persons =  js.Deserialize<Person[]>(json);

May not be the best answer, since we may not always have access to the code of the Web Server. I'll be leaving this open for a while longer.

Upvotes: 1

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