Hi,
> -----Original Message-----
> From: David Rault [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, January 31, 2002 11:36 AM
> To: Tomcat Users List
> Subject: Re: multiple init() calls
>
>
> hi
>
> i think there may be a misunderstanding (or i misunderstood your
> message ?!)
> the servlet must create _only_ one instance of each servlet class per web
> application
I believe there is no such MUST in spec.
> then this instance must receive _one_ message init()
> at this point user request may be served
> for each user request, a thread is started and executes the service(...)
> method on the
> _shared_ instance
>
> the singleThreadModel only tells the servlet engine not to serve several
> request simultaneously
> this is the behaviour required by the J2EE specs
>
> as for your problem, i'm doing servlet for about 2 years now and
> i never saw
> that kind of
> behaviour... may be a look at your code would help...
>
So, lets turn to spec (Servlet 2.3)
<cite>
SRV.14.2.20 SingleThreadModel
public interface SingleThreadModel
Ensures that servlets handle only one request at a time. This interface has no
methods.
If a servlet implements this interface, you are guaranteed that no two threads will
execute concurrently in the servlet?s service method. The servlet container can
make this guarantee by synchronizing access to a single instance of the servlet, or
by maintaining a pool of servlet instances and dispatching each new request to a
free servlet.
This interface does not prevent synchronization problems that result from servlets
accessing shared resources such as static class variables or classes outside the
scope of the servlet.
</cite>
I believe TC (at least 4.0.2b2) chose the second variant. The pool of instances.
So any instance have to be properly initialized.
just an example
package webtests;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
public class SingleThread extends HttpServlet implements SingleThreadModel {
private static int cnt = 0;
private static final String CONTENT_TYPE = "text/html; charset=windows-1251";
/**Initialize global variables*/
public void init() throws ServletException {
System.err.println("init at " + Thread.currentThread().toString());
System.err.println("Counter: " + (++cnt));
System.err.println("Instance: " + this.toString());
}
/**Process the HTTP Get request*/
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
response.setContentType(CONTENT_TYPE);
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<head><title>SingleThread</title></head>");
out.println("<body>");
out.println("<p>The servlet has received a GET. This is the reply.</p>");
out.println("</body></html>");
}
}
and TC console:
init at Thread[HttpProcessor[8080][0],5,main]
Counter: 1
Instance: webtests.SingleThread@19dc16
init at Thread[HttpProcessor[8080][0],5,main]
Counter: 2
Instance: webtests.SingleThread@405d3b
BTW, I'm not sure but it looks like TC3.2 creates only one instance.
Sorry, cant use attachments due to some "security" restrictions.
:E
> have fun!
>
> David
>
Anton.
--
To unsubscribe: <mailto:[EMAIL PROTECTED]>
For additional commands: <mailto:[EMAIL PROTECTED]>
Troubles with the list: <mailto:[EMAIL PROTECTED]>
