On Tue, 18 Dec 2001, Marcus Crafter wrote:
> Hi Berin,
>
> On Tue, Dec 18, 2001 at 11:20:18AM -0500, Berin Loritsch wrote:
> >
> > In what way are the same set of parameters used by different threads in
> > Cocoon?
> >
> > We never addressed ThreadSafety as one of the Contracts for either
> > Parameters
> > or Configuration.
>
> Have a look at this snippet from a generated sitemap:
>
> ----------------------
> public class sitemap_xmap extends AbstractSitemap {
> static final String LOCATION = "org.apache.cocoon.www.sitemap_xmap";
>
> static {
> dateCreated = 1007984808622L;
> }
>
> /** An empty <code>Parameter</code> used to pass to the sitemap components
> */
> private Parameters emptyParam = new Parameters();
>
> /** HashMap relating labels to view names */
> private HashMap view_label_map = new HashMap(1);
>
> <snip>...
>
> if (isSelected("userstatus", "permitted", listOfMaps,
> emptyParam, objectModel)) {
> ----------------------
>
> The 'emptyParam' is passed into several cocoon components. If a
> developer sets a parameter in a selector for example, then 2
> threads can overwrite each other with different results (the current
> problem we have here).
>
> In Cocoon I think the problem is more fundamental in that the
> parameters object is actually an instance level reference in the
> sitemap object (I'm not sure if that was intended ? ie. to share
> parameters between pipelines), but I think even a thread safe
> parameters object would not fix thread safety there - there
> needs to be a local Parameters object per thread passing through
> the sitemap, or a read-only Parameters object if the developer
> shouldn't be doing this at all.
I see what you mean. I've obviously never really looked at the
Parameters interface but now I've realized that there isn't similarity
with the Configuration class which *is* an interface whereas
Parameters is *not*. I don't know the intention why Parameters are
not designed like Configuration.
Any comments from core Avalonians why Parameters isn't an interface?
Giacomo
>
> If the Parameters object remains thread unsafe, perhaps it should be
> documented in it's class level javadocs like the Collection
> classes so it's obvious to the developer (I'll submit a patch if
> you like ?).
>
> Cheers,
>
> Marcus
>
>
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