Raj wrote:
> Hi all,
> I have few doubts to be clarified in designing our Web framework. I will
> appreciate, if you can provide me the guidance in the following issues
> regarding Singleton. ...
Hi Raj,
I also want to know how to use Singleton_type_class in Servlet :-)
but now I am not clear :-) , I just guess the following problems are
very Similar :-)
* cocurrent programming in Servlet
* with SingleThreadModel
* with field to lock the code
* with "synchronized method" to lock the code
* "dynamic data" for every "client requesting"
* how to use Singleton_type_class in Servlet
* where to instantiate it
* when to instantiate it
I think the reason is because that now I don't know some "basic
concepts" of how a special servlet engine works :-) :-)
The following are my guessing and questions :-)
* I think we can instantiate a Singleton_type_class in :
[Initialization] or [static/non-static Initialization block]
please read a new book :-) -- "The Java Programming
Language Third Edition" ISBN:0-201-70433-1 , from
P43 :-)
* "init method" -- ? :-)
* I find I can not write any [class constructor] in my Servlet
class if I use Jsdk2.1(windows), otherwise I will get a
java.lang.InstantiationException :-) , is it because
Servlet is one kind of "let" -- like applet ? :-)
* now I guess perhaps the better way for "sync/lock code"
is "implements SingleThreadModel" if we don't know
the "detail" of Servlet engine, and I guess perhaps all
the Servlet engine will support this way :-)
* and I find the following in the link --
http://forum.java.sun.com/read/16788242/qAoe_a1EClu0AAYpf#LR
...
That means: SingleThreadModel just like declare method
service () synchronized. It's "thread safety".
public synchronized void service (ServletRequest req ,
ServletResponse res) throws ServletException, IOException ;
...
* I also got the similar result from my testing -- I find the "whole
service method" has been locked, and I guess it is "global
locked in Servlet engine"
*But if we only want to lock part of our code in service(or doGet/doPost),
for example, we want to make [the code for "analysing input data"]
"multi-thread", but we want to make [the code for EJB or DB operating]
"singe-thread", now is the following possible? :-)
* put [the code for EJB or DB operating] in another Servlet class which
implements SingleThreadModel - servlet_2
* in servlet_1, after "analysing input data", then
response.sendRedirect(response.encodeRedirectURL("/servlet/servlet_2"));
BTW, I guess perhaps Servlet is one of the "Entrance of the whole Server-side
Java world" :-) -- it is "Jim Morrison -- the Doors :-) :-) , so I want to
know the
above concepts very clearly, could anybody give me direction about that?
thanks very much :-)
Thanks in advance!
Bo
Oct.16, 2000
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