Consuming RESTful C# Web Service through Java Android

Question

Dears,

I know that the title seems popular and easy but what I'm facing is too strange.

Simply, I have a RESTful C# .NET 4.0 web service published on the server, and I want to consume it through Java in my Android application, easy?

The problem is: whenever I call the .NET web service and get the response, java could not parse the return string into Json.

Error message:

org.json.JSONException: Value {lhs:"1 Euro",rhs: "1.3711 U.S. dollars",error: "",icc: true} of type java.lang.String cannot be converted to JSONObject
    at org.json.JSON.typeMismatch(JSON.java:111)
at org.json.JSONObject.<init>(JSONObject.java:158)
at org.json.JSONObject.<init>(JSONObject.java:171)
at com.itrack21.mobileapp.LoginActivity.getUserInfo(LoginActivity.java:151)
at com.itrack21.mobileapp.LoginActivity$1$1.run(LoginActivity.java:114)
at java.lang.Thread.run(Thread.java:841)
threadid=17: thread exiting with uncaught exception (group=0x4164d700)

Java Code:

public void getRate(String link) {

        try {
                URL url = new URL(link);
                URLConnection connection = url.openConnection();
                InputStream str = connection.getInputStream();
                InputStreamReader reader = new InputStreamReader(str);
                BufferedReader bufReader = new BufferedReader(reader);
                String line=new String();
                StringBuffer buffer = new StringBuffer();

                while( (line=bufReader.readLine()) != null) {
                    buffer.append(line);
                }

            JSONObject obj = null;
            try {
                obj = new JSONObject(buffer.toString());
            } catch (JSONException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }

            String rhs = "";
            try {
                rhs = obj.getString("rhs");
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            Log.i("getRate","Converted Currency = " + rhs.toString());

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

Debugging:

I did many debugging scenarios but with no luck, here I will use strangest one to describe the problem.

1. I use my java code to consume Google web service for currency converting using the following link http://www.google.com/ig/calculator?hl=en&q=1USD=?EUR and I got the response as follows: {lhs: "1 US dollar",rhs: "0.726321906 Euros",error: "",icc: true} . And here my code is working perfectly.

2. I copy exact Json value return from Google web service and working fine with my code, and return it as a HARD CODED String in my RESTful C# service as follows:

C# Code:

public string GetInfo()
{
return "{lhs:\"1 Euro\",rhs: \"1.3711 U.S. dollars\",error: \"\",icc: true}";
}

1. I request my C# .NET web service using the same code used to invoke Google web service bu I got error listed above org.json.JSONException: Value {lhs:"1 Euro",rhs: "1.3711 US dollars",error: "",icc: true} of type java.lang.String cannot be converted to JSONObject at org.json.JSON.typeMismatch(JSON.java:111) .

2. When I copy and paste the return value into my code as a HARD CODE, it works just fine.

    JSONObject obj = null; try { obj = new JSONObject("{lhs:\\"1 Euro\\",rhs: \\"1.3711 US dollars\\",error: \\"\\",icc: true}"); } catch (JSONException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } 

Many "Crazy" debugging scenario done including changing the server itself, but with no luck.

What I'm doing wrong?

Regards,

Answer 1

In JSON, you need to wrap the keys in quotation marks too. So for this:

{lhs: "1 US dollar",rhs: "0.726321906 Euros",error: "",icc: true} ,

you will have to do this:

{"lhs": "1 US dollar","rhs": "0.726321906 Euros","error": "","icc": "true"}

You can check your JSON online at : http://jsonlint.com/

Answer 2

After long debugging process, I got the cause, and then the solution. Here we go:

1. Visit Google Maps Web Service through Chrome browser, and you will get Json response. For debugging purpose, right click on page and select View page source . Note that the string of Json is pure Json with no additions.

2. When you repeat same procedure with the C# .NET response through Chrome browser, you will notice that the response is NOT pure Json, it is surrounded by this: <string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">{JSON String HERE}</string> .

Solution:

To remove this string surrounding the response, you have to return Json string as System.IO.Stream . Here the required code changes:

public System.IO.Stream GetInfo()
{
    OutgoingWebResponseContext context = WebOperationContext.Current.OutgoingResponse;
    context.ContentType = "text/plain";
    return new System.IO.MemoryStream(ASCIIEncoding.Default.GetBytes("{lhs:\"1 Euro\",rhs: \"1.3711 U.S. dollars\",error: \"\",icc: true}"));
}

This solution works fine with me, but is it optimal solution? converting from object to Json, and then from Json string to bytes is little overhead, what do think? suggestions?