How to make a Post Json rpc using java.net

I have to make a https post to a json-rpc api which wants to have a variable in the url. In this case:

https://mese.webuntis.com/WebUntis/jsonrpc.do?school=GS+T%C3%BCbingen


(this is a public server not my own so hack away).
The Server only accepts https and refuse to do anything without the Schoolname(GS+T%C3%BCbingen):

"jsonrpc":"2.0","id":"error","error":"message":"invalid schoolname","code":-8500


Additionally want to use the default java.net library.

I Got it to accept the Schoolname with this response:

"jsonrpc":"2.0","id":null,"error":"code":-32700,"message":"Parse error: No content to map due to end-of-inputn at [Source: org.apache.catalina.connector.CoyoteInputStream@396fcdd0; line: 1, column: 0]"


Now i have to add the Json data to my post but when i try to. It gives me the inavid schoolname response agin.

I tryed a few thing but im bad at java, here is my current code.

public class Main {

private final String USER_AGENT = "Mozilla/5.0";


public static void main(String args)

Main http = new Main();
String output;
String data;
String dataEncoded;
String schoolName;
String url;

data = ""id":"ID","method":"authenticate","params":"user":"ANDROID","password":"PASSWORD", "client":"CLIENT","jsonrpc":"2.0"";
dataEncoded = "%7B%22id%22%3A%22ID%22%2C%22method%22%3A%22authenticate%22%2C%22params%22%3A%7B%22user%22%3A%22ANDROID%22%2C%20%20%22password%22%3A%22PASSWORD%22%2C%20%22client%22%3A%22CLIENT%22%7D%2C%22jsonrpc%22%3A%222.0%22%7D";
schoolName = "GS+T%C3%BCbingen";// gs tübingen encoded for http
url = "https://mese.webuntis.com/WebUntis/jsonrpc.do";

System.out.println("nTrying Https Post to: " + url + " with SchoolName: " + schoolName + " with data: " + data);
output = http.sendPost(url,schoolName,data);
System.out.println("---Response Start---n" + output + "n---Response End---");




private String sendPost(String url,String schoolName,String data)
try
URL obj = new URL(url);
HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();

con.setRequestMethod("POST");
con.setRequestProperty("User-Agent", USER_AGENT);
//con.setRequestProperty("Content-Type", "application/json-rpc");
//con.setRequestProperty("", data);

String urlParameters = "school=" + schoolName ;//+ "&" + data;

con.setDoOutput(true);
DataOutputStream wr = new DataOutputStream(con.getOutputStream());
wr.writeBytes(urlParameters);
wr.flush();
wr.close();


BufferedReader in = new BufferedReader(
new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();

while ((inputLine = in.readLine()) != null)
response.append(inputLine);

in.close();
return response.toString();

catch(IOException e)
return "sensPost() failed: "+ e.getMessage();





I found out that i have to insert the json data into the html body but i have no idea how to and if that data also has to be ascii-% encoded.(Sorry for my mesy code but this is just for testing befor proper implementation.)

-Sammy

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