cURL e HttpURLConnection - Post JSON Data

Question

Come postare dati JSON utilizzando HttpURLConnection? Sto cercando in questo modo:

HttpURLConnection httpcon = (HttpURLConnection) ((new URL("a url").openConnection())); 
httpcon.setDoOutput(true); 
httpcon.setRequestProperty("Content-Type", "application/json"); 
httpcon.setRequestProperty("Accept", "application/json"); 
httpcon.setRequestMethod("POST"); 
httpcon.connect(); 

StringReader reader = new StringReader("{'value': 7.5}"); 
OutputStream os = httpcon.getOutputStream(); 

char[] buffer = new char[4096]; 
int bytes_read;  
while((bytes_read = reader.read(buffer)) != -1) { 
    os.write(buffer, 0, bytes_read);// I am getting compilation error here 
} 
os.close(); 

sto ottenendo errore di compilazione in linea 14.

La richiesta è cURL:

curl -H "Accept: application/json" \ 
-H "Content-Type: application/json" \ 
-d "{'value': 7.5}" \ 
"a URL" 

È questo il modo di gestire la richiesta cURL? Qualsiasi informazione mi sarà molto utile.

Grazie.

Answer 1

OutputStream prevede di lavorare con i byte e di trasmetterli ai personaggi. Prova questo:

HttpURLConnection httpcon = (HttpURLConnection) ((new URL("a url").openConnection())); 
httpcon.setDoOutput(true); 
httpcon.setRequestProperty("Content-Type", "application/json"); 
httpcon.setRequestProperty("Accept", "application/json"); 
httpcon.setRequestMethod("POST"); 
httpcon.connect(); 

byte[] outputBytes = "{'value': 7.5}".getBytes("UTF-8"); 
OutputStream os = httpcon.getOutputStream(); 
os.write(outputBytes); 

os.close(); 

Answer 2

Si consiglia di utilizzare la classe OutputStreamWriter.

final String toWriteOut = "{'value': 7.5}"; 
final OutputStreamWriter osw = new OutputStreamWriter(connection.getOutputStream()); 
osw.write(toWriteOut); 
osw.close();