Question

I have a Java application communicating with a SQL database via a PHP script, using JSON. I have used JSON before to json_encode an array, that works fine, you can call the values in Java by using the key of each entry. But now, I json_encoded a string in PHP, like this:
json_encode("Succes!");
Now, how do I request that value in the Java side of business? I need something to put into jsonResponse.getString('key'); as a key. What is the key…

I hope you understand my question…

public String send(String username, String password, String database){
    //Create a HTTPClient as the form container
    HttpClient httpclient;

//Use HTTP POST method
HttpPost httppost;

//Create an array list for the input data to be sent
ArrayList<NameValuePair> nameValuePairs;

//Create a HTTP Response and HTTP Entity
HttpResponse response;
HttpEntity entity;

//Create new default HTTPClient
httpclient = new DefaultHttpClient();

//Create new HTTP POST with URL to php file as parameter
httppost = new HttpPost("http://192.168.144.150/login/add.php");

String pass = md5(password);

//Next block of code needs to be surrounded by try/catch block for it to work
try {
    //Create new Array List
    nameValuePairs = new ArrayList<NameValuePair>();

    //place them in an array list
    nameValuePairs.add(new BasicNameValuePair("username", username));
    nameValuePairs.add(new BasicNameValuePair("password", pass));
    nameValuePairs.add(new BasicNameValuePair("database", database));

    //Add array list to http post
    httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

    //assign executed form container to response
    response = httpclient.execute(httppost);

    //check status code, need to check status code 200
    if(response.getStatusLine().getStatusCode()== 200){

        //assign response entity to http entity
        entity = response.getEntity();

        //check if entity is not null
        if(entity != null){


            //Create new input stream with received data assigned
            InputStream instream = entity.getContent();

            //Create new JSON Object. assign converted data as parameter.
            //JSONObject jsonResponse = new JSONObject(convertStreamToString(instream));
            JSONArray a = new JSONArray(convertStreamToString(instream));

            //assign json responses to local strings
            String res = a.getString(0);

            //Return the json response to the gui
            return res;

        } else {
            //Toast.makeText(this, "kapot", Toast.LENGTH_SHORT).show();
            return new String("De entiteit is leeg. Kortom: kapot");
        }


    } else {
        //Toast.makeText(this, "statuscode was niet 200", Toast.LENGTH_SHORT).show();
        return new String("De statuscode was niet 200.");
    }


} catch(Exception e){
    e.printStackTrace();
    //Display toast when there is a connection error
    //Change message to something more friendly
    //Toast.makeText(this, "verbindingsproblemem", Toast.LENGTH_SHORT).show();
    return new String("Er is een fout opgetreden. Controleer a.u.b. uw gegevens en de internetverbinding.");
}

Don’t mind the Dutch parts, it’s unimportant.

Answer 1

The output of json_encode("Success!") is "Success", which isn’t in and of itself a valid JSON document. A valid JSON document’s top-level entity (the root) must be an object or an array.

If you want to just return a single string, you might do that by:

1. Making it the only entry in an array:

   json_encode(array("Success!"))
   

   …which results in ["Success!"], which you can use like this in your Java code (since you say you’re using the org.java library):

   JSONArray a = new JSONArray(jsonStringFromPHP);
   String s = a.getString(0);
   

   or of course

   String s = new JSONArray(jsonStringFromPHP).getString(0);
   

2. Or making it the only property of an object:

   json_encode(array('result' => "Success!")
   

   …which results in {"result":"Success!"}, which you can use like this in your Java code:

   JSONObject o = new JSONObject(jsonStringFromPHP);
   String s = o.getString("result");
   

or of course

    String s = new JSONObject(jsonStringFromPHP).getString("result");

You could probably use JSONTokenizer to read your current JSON fragment ("Success!"), but I wouldn’t suggest going that way. Stick to exchanging valid JSON documents.