Thanks for the reply. I thought as much, but regarding your second point, I
wasn't thinking about a second servlet acquiring a reference to the original
servlet, but instead, the original servlet storing a reference to itself.
In such a case, the servlet container could not guarantee that there are no
dangling references.
David
> -----Original Message-----
> From: Craig R. McClanahan [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, November 18, 1999 1:35 PM
> To: David Chisholm
> Cc: [EMAIL PROTECTED]
> Subject: Re: [Fwd: Question about Servlet lifetime]
>
>
> David Chisholm wrote:
>
> > Would the technique for preventing singleton objects from being garbage
> > collected (as described in Doug Leah's Concurrent Programming in Java, I
> > think) also prevent servlets from being unloaded? Basically,
> the technique
> > calls from creating a thread that contains a reference to the singleton.
> > The thread doesn't do anything, but because the VM maintains a
> reference to
> > this thread, the thread cannot be gc'd and thus neither can the
> singleton.
> >
>
> The issue with servlets isn't really the same one. The "garbage
> collection"
> problem on singletons happens because there is no live reference
> to them. With
> servlets, unloading is a deliberate action that the server is
> explicitly allowed
> to take, if it wants to. The servlet container might choose to
> unload a servlet
> that hasn't been used for a long time, in order to make room (in
> memory) for a
> newly requested one that has never been loaded yet.
>
> >
> > So, if a servlet is used in place of the singleton, can a
> servlet container
> > unload the servlet even though a reference to that servlet
> still exists? I
> > would think 'yes, it can', and it would cause unpredictable results.
> >
>
> In the 2.1 and 2.2 servlet APIs, there is no longer any legal way for an
> application-level object (servlet or JavaBean) to acquire a
> reference to another
> servlet instance. Therefore, the server can guarantee that there are no
> dangling references to the servlet instance when it is unloaded,
> as long as it
> manages its own references correctly.
>
> >
> > Just curious if anyone else had considered this and knows for
> certain, or
> > has opinions on, what would happen.
>
> > David
> >
>
> Craig
>
>
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