Android HttpURLConnection

gistfile1.txt

try {
    URL url = new URL("http://www.caelum.com.br/mobile");
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestProperty("Accept", "application/json");
    connection.setRequestProperty("Content-type", "application/json");

    //coloca o json no corpo do POST
    connection.setDoOutput(true);
    PrintStream printStream = new PrintStream(connection.getOutputStream());
    printStream.println(json);

    //envia para o servidor
    connection.connect();

    //trata resposta (que no nosso caso só tem uma linha)
    String jsonDeResposta = new Scanner(connection.getInputStream()).next();
    return jsonDeResposta;
} catch (Exception e) {
    throw new RuntimeException(e);
}