How to enter to .aspx page by http connection using http POST request

I m facing dificulty with http "POST" request.

i need to login to a website " "
it requires username and password.

i dont know how to enter username and password so that i can access the
page by myjava class.

i m using this code gor gettinh request:

public static String GetRequest() throws IOException {

String urlString = "";;
DataInputStream dis = null;
StringBuffer message = new StringBuffer();
String outputMessage = new String();
URL url = new URL(urlString);
HttpURLConnection httpConnection =
(HttpURLConnection) url.openConnection();
Properties props = System.getProperties();
props.put("http.proxyHost", "SERVER");
props.put("http.proxyPort", "8080");


dis = new DataInputStream(httpConnection.getInputStream());
int ch;
while ((ch = != -1) {
message.append((char) ch);
outputMessage = message.toString();
return outputMessage;

now if i change request method to POST , then plz tell me how can i
enter username and password by my java code.