Why do you have to call URLConnection#getInputStream to be able to write out to URLConnection#getOutputStream?
- by John
I'm trying to write out to URLConnection#getOutputStream, however, no data is actually sent until I call URLConnection#getInputStream. Even if I set URLConnnection#doInput to false, it still will not send. Does anyone know why this is? There's nothing in the API documentation that describes this.
Java API Documentation on URLConnection: http://download.oracle.com/javase/6/docs/api/java/net/URLConnection.html
Java's Tutorial on Reading from and Writing to a URLConnection: http://download.oracle.com/javase/tutorial/networking/urls/readingWriting.html
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.URL;
import java.net.URLConnection;
public class UrlConnectionTest {
private static final String TEST_URL = "http://localhost:3000/test/hitme";
public static void main(String[] args) throws IOException {
URLConnection urlCon = null;
URL url = null;
OutputStreamWriter osw = null;
try {
url = new URL(TEST_URL);
urlCon = url.openConnection();
urlCon.setDoOutput(true);
urlCon.setRequestProperty("Content-Type", "text/plain");
////////////////////////////////////////
// SETTING THIS TO FALSE DOES NOTHING //
////////////////////////////////////////
// urlCon.setDoInput(false);
osw = new OutputStreamWriter(urlCon.getOutputStream());
osw.write("HELLO WORLD");
osw.flush();
/////////////////////////////////////////////////
// MUST CALL THIS OTHERWISE WILL NOT WRITE OUT //
/////////////////////////////////////////////////
urlCon.getInputStream();
/////////////////////////////////////////////////////////////////////////////////////////////////////////
// If getInputStream is called while doInput=false, the following exception is thrown: //
// java.net.ProtocolException: Cannot read from URLConnection if doInput=false (call setDoInput(true)) //
/////////////////////////////////////////////////////////////////////////////////////////////////////////
} catch (Exception e) {
e.printStackTrace();
} finally {
if (osw != null) {
osw.close();
}
}
}
}
