----- Original Message -----
From: "Dick Zetterberg" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, October 09, 2003 10:07 AM
Subject: Re: [OS-webwork] Bug catching contest...
>
> Can't you just fix this by using a ConcurrentHashMap or a
ConcurrentReaderHashMap from the EDU.oswego.cs.dl.util.concurrent package
for the expressions?
> So the code would be something like:
>
> public static Object compile(String expression) throws OgnlException {
> Object o = null;
>
> o = expressions.get(expression);
>
> if (o == null) {
> o = Ognl.parseExpression(expression);
> expressions.put(expression, o);
> }
>
> return o;
> }
Actually this code wouldn't fix anything. The difference is that this code
is visibly not synchronized, while the previous code was unvisibly not
synchronized.
The point is that to make it working, both get and put must be in the same
synchronized block. Otherwise you may just leave it unsynchronized. In
fact - this code would probably work well even not synchronized. It would
sometimes do unnecessary compilations.
-- Mike
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