This tagging interface 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 servlets 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
This interface does not prevent synchronization problems that result
from servlets accessing shared resources such as class variables or
classes outside the scope of the servlet.
<B>NOTEB>: No provisions have been made for usage of the Servlet API in
a threaded environment. This interface is only provided for