Use Google volley api to send HTTP POST request of RDF data - rest

Question

So, I have recently integrated the Volley API in my app in order to provide a Cloud storage solution (REST). Since, i have never used the API before i have some trouble trying to send RDF (text/turtle) data via HTTP POST. The REST server is working perfectly since I send GET and POST requests (via the Postman Chrome app) and every time i receive 200 and 201 responses. Although i managed to send a simple GET request via the API, i get a 400 error when i send an HTTP POST.
The code is the following:
//the RDF turtle payload to send over HTTP POST
final String bodyPost = "#prefix : <http://xxx.xxx.xxx.gr/xxx/schema/xxx#> ." + "\n" +
"#prefix xsd: <http://www.w3.org/2001/XMLSchema#> ." + "\n" +
"[a :Patient ;" + "\n" +
":lastName "+'"'+"Aylakiotis"+'"'+"^^xsd:string ; " + "\n" +
":firstName "+'"'+"Yiannis"+'"'+"^^xsd:string ;" + "\n" +
":dateOfBirth "+'"'+"1970-04-14"+'"'+"^^xsd:date ;" + "\n" +
":amka "+'"'+"12345678903"+'"'+"^^xsd:string ;" + "\n" +
":gender :Male ;" + "\n" +
"] .";
RequestQueue queue = Volley.newRequestQueue(this);
final String URL ="http://xxx.xxx.xxx:8080/xxx/";
EditText folderTitle = (EditText) findViewById(R.id.folderTitle);
StringRequest strReq = new StringRequest(Request.Method.POST, URL,
new Response.Listener() {
#Override
public void onResponse(Object response) {
folderTitle.setText("Response is: " + response.toString().substring(0,500));
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
folderTitle.setText("Error: " + error.getMessage());
}
}) {
#Override
public byte[] getBody() throws AuthFailureError {
System.out.println("string post data: " + bodyPost);
if (params != null && params.size() > 0) {
System.out.println("string post data: " + bodyPost);
return encodeParameters(params, getParamsEncoding());
}
return bodyPost.getBytes();
}
#Override
public Map<String, String> getHeaders() throws AuthFailureError {
Map<String, String> headers = new HashMap<String, String>();
String creds = String.format("%s:%s", "xxx", "xxx");
String auth = "Basic " + Base64.encodeToString(creds.getBytes(), Base64.DEFAULT);
headers.put("Authorization", auth);
headers.put("Content-Type", "text/turtle");
return headers;
}
};
// Add the request to the RequestQueue.
queue.add(strReq);
String bodyPost is the data payload i want to send in a turtle RDF format. I am putting this in my getBody() method, however i still get a 400 bad request. I have already sent this String via POST http through the Postman Chrome app and it works (201 Created). I saw that most implementations had getParams() but this requires key/value pairs whereas i am using triples that i want to send as a whole string of raw data

Answer 1

Set your Content-type to text/turtle. Override your request header like this:
#Override
public Map<String, String> getHeaders() throws AuthFailureError {
final HashMap<String, String> params = new HashMap<String, String>();
params.put("Content-Type", "text/turtle");
return params;
}