Wondering if these 2 patterns could make sense:
- Pass clone of ModelFormField instance to renderer and have each
instanceof ModelFormField implement Cloneable contract. Could provide a
systematic way to improve thread safety
Wondering if that would be too expensive. 2 things that may help:
FlexibleStringExpander instances or any other immutable references could
be shared between cloned and 'this'. FlexibleStringExpander can be
assumed immutable.
Incremental gc in java could mitigate overhead.
- Restrict access or remove setXXX methods in ModelFormField instances.
Had similar problems a while back when i extended renderers/xsd in our
code. So feel the pain. Workaround was to use only context reference to
build pipeline if state needs to be carried and not change the object.
Harmeet
On 19/05/10 1:49 PM, Adrian Crum wrote:
Just a friendly reminder to the OFBiz developers and committers: The
screen widget model classes should not have their state altered by
renderers. That is not thread-safe and it results in undesirable behavior.
I know it's easy to forget - I just deprecated some methods that I wrote
where I made that mistake. :-)
It might help to think of the widget model classes as being immutable
(though technically they aren't). Once they are constructed and put in
the cache, they shouldn't be changed.
If you see code where a renderer calls a model's renderXxxx method, and
inside that method the model's fields are being changed, then that is a
no-no.
-Adrian
