PreferencesService might return invalid Preferences object for a user
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Key: FELIX-609
URL: https://issues.apache.org/jira/browse/FELIX-609
Project: Felix
Issue Type: Bug
Components: Preferences Service
Reporter: Angelo van der Sijpt
When a Preferences object has been obtained for a given user, it can be removed
using removeNode(). A following call to getUserPreferences(...) will then
return the old, now invalid, Preferences object, leading to an
IllegalStateException when trying to add new data to the node. From this moment
on, it is not possible to obtain a valid Preferences object for this user.
The spec does not provide a definite answer about this case; 106.4 comes
closest with "getUserPreferences(String) - Return a Preferences object
associated with the user name that is given as argument. If the user does not
exist, a new root is created atomically." Intuitively, one might expect that
removeNode() restores the PreferencesService to the same state it was before
getUserPreferences(...) was called.
The invalid Preferences object is caused by caching behavior in
PreferencesServicesImpl's getUserPreferences(...), which checks whether a
user's root node has already been created; if so, it will be returned, if not,
it will be created.
91 PreferencesImpl result = (PreferencesImpl) this.trees.get(name);
92 // if the tree does not exist yet, create it
93 if (result == null) {
94 result = new PreferencesImpl(new
PreferencesDescription(this.bundleId, name), this.storeManager);
95 this.trees.put(name, result);
96 }
The most plausible solution is to add an extra clause to the if-statement on
line 93, stating something like
93 if (result == null || result.isValid()) {
provided that isValid() will then return the valid field of PreferencesImpl.
An alternative would be to detect the removal of a node which does not have a
parent (is a root node), and then remove it from the PreferencesServiceImpl's
trees; this is not that complicated, but requires some extra code.
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