This is not really a question, however, I would like to share some of my working code here for your reference when you need.
As we know that HttpEntity
For those who are struggling to send utf-8 parameters and still no luck, the problem I had was in the dataOutputStream, and change the code of @RacZo to below code:
private void buildTextPart(DataOutputStream dataOutputStream, String parameterName, String parameterValue) throws IOException {
dataOutputStream.writeBytes(twoHyphens + boundary + lineEnd);
dataOutputStream.writeBytes("Content-Disposition: form-data; name=\"");
dataOutputStream.write(parameterName.getBytes("UTF-8"));
dataOutputStream.writeBytes(lineEnd);
dataOutputStream.writeBytes("Content-Type: text/plain; charset=UTF-8" + lineEnd);
dataOutputStream.writeBytes(lineEnd);
dataOutputStream.write(parameterValue.getBytes("UTF-8"));
dataOutputStream.writeBytes(lineEnd);
}