Java – sending HTTP parameters via POST method easily

In a GET request, the parameters are sent as part of the URL.

In a POST request, the parameters are sent as a body of the request, after the headers.

To do a POST with HttpURLConnection, you need to write the parameters to the connection after you have opened the connection.

This code should get you started:

String urlParameters  = "param1=a&param2=b&param3=c";
byte[] postData       = urlParameters.getBytes( StandardCharsets.UTF_8 );
int    postDataLength = postData.length;
String request        = "http://example.com/index.php";
URL    url            = new URL( request );
HttpURLConnection conn= (HttpURLConnection) url.openConnection();           
conn.setDoOutput( true );
conn.setInstanceFollowRedirects( false );
conn.setRequestMethod( "POST" );
conn.setRequestProperty( "Content-Type", "application/x-www-form-urlencoded"); 
conn.setRequestProperty( "charset", "utf-8");
conn.setRequestProperty( "Content-Length", Integer.toString( postDataLength ));
conn.setUseCaches( false );
try( DataOutputStream wr = new DataOutputStream( conn.getOutputStream())) {
   wr.write( postData );
}