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https://issues.apache.org/jira/browse/WICKET-5772?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14223098#comment-14223098
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Martin Grigorov commented on WICKET-5772:
-----------------------------------------
Looks like a safe change to me.
The only negative effect I see is that it may make second/third/... attempt to
load the model object in case it fails and the impl of #load() handles this
explicitly.
> LoadableDetachableModel caches null value if load() fails, bug in getObject()
> {attached = true;}
> ------------------------------------------------------------------------------------------------
>
> Key: WICKET-5772
> URL: https://issues.apache.org/jira/browse/WICKET-5772
> Project: Wicket
> Issue Type: Bug
> Components: wicket
> Affects Versions: 1.4.23, 6.18.0, 7.0.0-M4
> Reporter: Martin Makundi
> Assignee: Sven Meier
> Labels: easyfix, easytest, patch
> Original Estimate: 10m
> Remaining Estimate: 10m
>
> If you have a LoadableDetachableModel whose load() operation fails at an
> instance, the LoadableDetachableModel will cache null value because
> getObject() method sets attached = true; before load() invocation has
> returned.
> This results in methods trusting LoadableDetachableModel using the null value
> for their operations which is logically incorrect as null might not be a
> legal value at all. Such behavior would result in unexpected
> difficult-to-debug behavior in depending components.
> Easy fix:
> Move:
> attached = true;
> after line:
> transientModelObject = load();
> Test case:
> /**
> * LoadableDetachableModel must not return null as an attached value if
> load()
> * fails.
> */
> public void testWhenLoadFails() {
> final LoadableDetachableModel<Void> loadableDetachableModel = new
> LoadableDetachableModel<Void>() {
> /**
> * @see org.apache.wicket.model.LoadableDetachableModel#load()
> */
> @Override
> protected Void load() {
> throw new UnsupportedOperationException("Let's assume this fails for
> some reason.");
> }
> };
> try {
> loadableDetachableModel.getObject();
> fail(UnsupportedOperationException.class + " expected.");
> } catch (final UnsupportedOperationException e) {
> LoggerFactory.getLogger(LoadableDetachableModel.class).debug("Expected
> behavior due to " + UnsupportedOperationException.class);
> }
> try {
> assertNotSame(LoadableDetachableModel.class + " should not return null
> if it's load() has failed\n", null,
> loadableDetachableModel.getObject());
> } catch (final UnsupportedOperationException e) {
> LoggerFactory.getLogger(LoadableDetachableModel.class).debug("Expected
> behavior due to " + UnsupportedOperationException.class);
> }
> }
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