Calling API with JSON format gives the unknown format error

Question

I am calling an API with groovy code with Jason format data and the response we receive "Response code was 500" "��VJ-�/�M-.NLO-V��V��+I-�K�Q(N-K-R+P�Ձ�*������J7" Please help if anybody has faced the same issue.

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def payloadMap = ["project":["id":"12412"], "summary": "Test ticket for testing API 4", "assignee": ["name": "in22915194"], ] def payloadData = JsonOutput.toJson(payloadMap)

def url = new URL(uri);
// NOTE: The following removes all checks against SSL certificates
disableSSL();
def conn = url.openConnection(proxy);
conn.doOutput = true;

BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(conn.getOutputStream()));
writer.write(payloadData.toString().trim());
writer.flush();
writer.close();

     InputStream responseStream = conn.getInputStream();
     result = responseStream.getText();
     responseStream.close();