Keep connection alive?

Question

Hi.
I am trying to make a http connection to a site and reuse the connection to fetch several pages.
Here is the code I copied from java.sun.com and modified
import java.net.*;
import java.io.*;
public class URLConnectionReader {
    public static void main(String[] args) throws Exception {
        URL url= new URL("http://java.sun.com/docs/books/tutorial/networking/urls/readingWriting.html");
        URLConnection conn = url.openConnection();
        BufferedReader in = new BufferedReader(
                                new InputStreamReader(
                                conn.getInputStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null)
            System.out.println(inputLine);
        in.close();
            url  = new URL("http://java.sun.com/docs/books/tutorial/networking/sockets/index.html");
        conn = url.openConnection();
        in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        while ((inputLine = in.readLine()) != null)
            System.out.println(inputLine);
        in.close();
}When I call url.openConnection() again, a new connection is open and assigned to conn.
However, I don't want to have a new connection since the program will be slow if there are a lot of threads are running at the same time....also, there is some overhead time to create a new connection...
Is there anyway to reuse the existing connection?
Thanks.

Answer 1

In 1.4.x (I didn't check the other versions), there is a system property called http.keepAlive (http://java.sun.com/j2se/1.4.2/docs/guide/net/properties.html). By default this property is set to true. This will keep the connection to the server open for a limited time (I think it is in the order of 5 seconds). All this is done underwater in the networking libraries,
You could also checkout http://jakarta.apache.org/commons/httpclient/. It supports keepalive.
Cheers,
--Arnout