DO NOT REPLY [Bug 48088] New: Servlet implementing SingleThreadModel are initialized twice

https://issues.apache.org/bugzilla/show_bug.cgi?id=48088

           Summary: Servlet implementing SingleThreadModel are initialized
                    twice
           Product: Tomcat 5
           Version: 5.5.28
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Catalina
        AssignedTo: dev@...
        ReportedBy: anthony.goubard@...


When a Servlet implements javax.servlet.SingleThreadModel the method init is
called twice. This should not happen according to the Servlet specification.

http://developer.java.sun.com/developer/onlineTraining/Servlets/Fundamentals/servlets.html#lifeCycle

I first saw the bug when someone tried when someone submitted a bug in my open
source web services framework "xins"
http://sourceforge.net/tracker/?func=detail&aid=2884574&group_id=71598&atid=531814
(bug submitted from Linux with Tomcat 5.5.25)

Here the petstore demo is initialized at the start-up of Tomcat and with the
first request http://localhost:8080/petstore/. This apparently happens on the
same Servlet object.
I've attached the war file that contains removed code so that the Servlet
initializes correctly the first time without looking for a database.
Source code and Demo available at http://xins.sourceforge.net/

I've tried to reproduce it (See code below) and had a slightly different
behaviour:
The init method is called twice but at the first request and it seems to be
done on 2 different objects as the exception is not thrown. The destroy method
is also called twice at the end.

public class SimpleServlet extends HttpServlet implements
javax.servlet.SingleThreadModel {

    private boolean initialized = false;
    private int initCount = 0;

    public void init(ServletConfig config)
        throws IllegalArgumentException, ServletException {
        if (initialized) {
            throw new ServletException("Servlet already initialized. Should not
happen according to the specs.");
        }
        initialized = true;
        System.err.println("------------ Initialized -");
        initCount++;
    }


    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws ServletException, IOException {

        PrintWriter out = response.getWriter();
        out.println("SimpleServlet Executed " + initCount);
        out.flush();
        out.close();
    }

    public void destroy() {
        initialized = false;
        System.err.println("------------ destroy");
    }
}

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https://issues.apache.org/bugzilla/show_bug.cgi?id=48088

Mark Thomas <markt@...> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WORKSFORME

--- Comment #1 from Mark Thomas <markt@...> 2009-11-06 13:39:44 GMT ---
When a servlet implements javax.servlet.SingleThreadModel multiple instances of
the Servlet will be created to provide a pool of Servlet objects. This looks
like what you are seeing.

If this does not explain what you are seeing, please re-open and attach a test
case that demonstrates the problem.

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