Re: Instantiate expensive object *once* in JSP/Tomcat

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <>
Sat, 27 Jan 2007 22:20:13 -0500
Robert Klemme wrote:

On 27.01.2007 17:15, Arne Vajh?j wrote:

Dave wrote:

I have an object that is very expensive in terms of time (it reads in
an XML mapping file).

How do I load this object into memory once - and once only - when the
server starts? How do I access this object in my standard JSP code?

One idea:
  - make it a singleton
  - create a startup servlet that references it

A more proper solution is to implement the interface that listens to
application events. The startup event would create that object and
place it in the web application's context while the shutdown even would
trigger cleanup code.

Regarding application context instead of singleton: then in general
that is a very bad design because all the code using it becomes
tied to being used in web app context. If it is only to be used
in JSP pages then no problem, they are already tied to web app

Regarding ServletContextListener instead of startup servlet: fine.


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