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https://issues.apache.org/jira/browse/WICKET-1784?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12622483#action_12622483
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R. Goodwin commented on WICKET-1784:
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Johan,
If only IDataProvider was altered, then yes the call to
onRequestsData(offset,count) requires size() first as the problem has not been
fixed throughout.
I was thinking more of a redesign of the exchange throughout to cope with
services providing an all-in-one Transfer Object.
A good start might be looking again at the order in which things are done in
AbstractPageableView.getItemModels().
Igor,
Subclassing RefreshingView can only be a short term solution, as one loses the
paging functionality from AbstractPageableView downwards.
And anyway, IDataProvider is looks very much like it was meant to be
persistence method agnostic, whether that be a hookup with a database, Lucene
search engine etc.
I am confident with persisting with this request, as we've been running a
number of succesful servlet/JSP web apps rendering Lucene results with paging
for the last few years. And the exchange of data between UI tier and services
tier is not unlike the 'single call' Transfer Object model.
> Enhance IDataProvider to support applications using the Transfer Object J2EE
> pattern
> ------------------------------------------------------------------------------------
>
> Key: WICKET-1784
> URL: https://issues.apache.org/jira/browse/WICKET-1784
> Project: Wicket
> Issue Type: Improvement
> Components: wicket
> Affects Versions: 1.3.3, 1.4-M3
> Environment: Wicket 1.3.3 and 1.4-M3
> Reporter: R. Goodwin
> Assignee: Igor Vaynberg
>
> In some environments searches are performed in 'single call' fashion, using a
> transfer object.
> E.g. two queries performed by the data services tier before returning
> combined results to the UI tier:
> i. Query for paged search results
> ii. Query for a 'count' value representing total possible results
> The contract between DataView and IDataProvider does not support a 'single
> call' environment as the give/take relationship between these classes is
> biased towards DataView.
> DataView expects IDataProvider to provide it's size before providing
> IDataProvider with its offset and count.
> * DataView may have good reasons for needing size before it can provide
> offset/count.
> * But IDataProvider has equally good reasons for needing offset/count before
> it can provide size.
> The circular dependency:
> 1. DataView calls IDataProvider.size()
> 2. IDataProvider cannot return size as it cannot start a query until it
> receives offset/count from DataView
> 3. These it does not receive until DataView calls IDataProvider.iterator()
> later on
> Others who experienced this problem (with CODE examples):
> * http://www.nabble.com/IDataProvider-and-Hibernate-Search-td15546101.html
> * http://www.mail-archive.com/[EMAIL PROTECTED]/msg14266.html
> ---
> The suggested solution of caching the combined search results and count value
> does not work if the search cannot begin until offset and count are
> available. And writing a custom DataView is not feasible either time wise as
> I understand that it cannot be done without needing to write a number of
> other classes too.
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