Connecting to Servlet Using URLConnection

[Lame, John]

I have a method which opens a connection to a servlet, posts some
data, and reads the output.  If I call the method twice with the same
parameters, it succeeds the first time but fails the second time.

I've moved the offending code to a separate Java Application in which
I execute the connect--read--write sequence inside a loop.  The code
and output are as follows.  I loop 4 times.  The operation succeeds
the first time, fails the second, succeeds the third time, and hangs
the fourth time (very strange).

=========BEGIN CODE===========
import java.util.*;
import java.io.*;
import java.net.*;

public class GetSecret {
  public static void main(String Argv[]) {

    URLConnection uc = null;
    BufferedReader in = null;
    PrintWriter out = null;
    URL u = null;
    boolean success;

    try {
        u = new URL("http://mydomain/MyServlet");
        for (int i=0; i<4; i++) {
           System.out.println("Open connection " + i);

           // Set up the Connection
           uc = u.openConnection();
           uc.setDoInput(true);
           uc.setDoOutput(true);

          // Set the form parameters
          out = new PrintWriter(uc.getOutputStream());
          out.print("secret_key=" + URLEncoder.encode("12-#3"));
          out.close();

          // Get the response.  The NullPointerException happens on
          // the uc.getInputStream() line below which is why I have
          // placed it inside its own try-catch block.
          try {
            in = new BufferedReader(new
InputStreamReader(uc.getInputStream()));
            System.out.println("BEGIN RESPONSE " + i);
            // Normally I would get the entire response, but this is just a
test.
            System.out.println(in.readLine().substring(0,1));
            System.out.println("END RESPONSE " + i);
            in.close();
          }
          catch (java.lang.NullPointerException e) {
            System.out.println("FAILED");
            e.printStackTrace();
          }
          System.out.println("Close connection " + i);
       }
    }
    catch (java.net.MalformedURLException e) {
      e.printStackTrace();
    }
    catch (java.io.IOException e) {
      e.printStackTrace();
    }
  }
}
==========END CODE============


====OUTPUT======
Open connection 0
BEGIN RESPONSE 0
<
END RESPONSE 0
Close connection 0
Open connection 1
FAILED
java.lang.NullPointerException
        at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:473)
        at
sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection
.java:408)
        at GetSecret.main(GetSecret.java:43)
Close connection 1
Open connection 2
BEGIN RESPONSE 2
<
END RESPONSE 2
Close connection 2
Open connection 3
===============

I can fix the problem by sleeping (for about 12 seconds in this case) after
ever iteration of the loop.  However, this is not an acceptable solution
since I have no way of knowing how long to wait.

Any idea what's going on here?

Thanks in advance,
John

___________________________________________________________________________
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff SERVLET-INTEREST".

Archives: http://archives.java.sun.com/archives/servlet-interest.html
Resources: http://java.sun.com/products/servlet/external-resources.html
LISTSERV Help: http://www.lsoft.com/manuals/user/user.html