[
https://issues.apache.org/jira/browse/TAP5-795?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Peter Stavrinides updated TAP5-795:
-----------------------------------
Summary: Tapestry IoC should provide an OrderedConfiguration for
EagerLoaded services (was: Tapestry IoC should provide an OderedConfiguration
for EagerLoaded services)
> Tapestry IoC should provide an OrderedConfiguration for EagerLoaded services
> ----------------------------------------------------------------------------
>
> Key: TAP5-795
> URL: https://issues.apache.org/jira/browse/TAP5-795
> Project: Tapestry 5
> Issue Type: Improvement
> Components: tapestry-ioc
> Affects Versions: 5.1
> Environment: Any
> Reporter: Peter Stavrinides
> Priority: Critical
>
> It is mentioned in the documentation that the order in which services are
> created is not defined when using eagerLoad().
> You can get into serious trouble If ordering of eagerloaded services is
> important (and it often is) by using :
> binder.bind(ImageService.class).eagerLoad();
> It can produce a NPE or work just fine and go undetected, so is a ticking
> time bomb. Perhaps this method should be renamed to eagerLoadUnordered() or
> removed entirely, and a way of ordering these would be great to have. An
> illustrative example is given below with two eagerloaded services
> (SiteInitialise sets up database connections and the connection pool,
> ImageService loads a cache of image data, so implicitly requires
> SiteInitialise to be loaded first).
> //Example: The shell of the eagerloaded ImageService service
> public class ImageService {
> /** Cache to hold thumbnail images */
> private static ConcurrentHashMap<Integer, Thumbnail>
> imageCache_ = new ConcurrentHashMap<Integer, Thumbnail>();
>
> public void preloadImageCache() {
> DbConnection connection = null;
> try {
> //This can potentially turn into a Null Pointer
> Exception as the startup order is arbitrary
> connection =
> DatabaseConnection.getReadConnection();
> //database query
> } catch (Exception e) {
> //handle exception
> }
> }
> public static ImageService build() {
> return new ImageService();
> }
> public ImageService() {
> preloadImageCache();
> }
> }
> //Workaround: adding a dependency on the other eagerloaded service solves
> it, but this is not a practical solution if there are many of these
> services
> public class ImageService {
> /** Cache to hold thumbnail images */
> private static ConcurrentHashMap<Integer, Thumbnail>
> imageCache_ = new ConcurrentHashMap<Integer, Thumbnail>();
>
> public void preloadImageCache() {
> DbConnection connection = null;
> try {
> connection =
> DatabaseConnection.getReadConnection();
> //database query
> } catch (Exception e) {
> //handle exception
> }
> }
> public static ImageService build(SiteInitialise
> siteInitialise) {
> return new ImageService(siteInitialise);
> }
> public ImageService(SiteInitialise siteInitialise) {
> if(siteInitialise.isConnectionOk())
> preloadImageCache();
> }
> }
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
