Martin Desruisseaux created SIS-73:
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Summary: Remove the automatic mapping of UUIDs to objects
Key: SIS-73
URL: https://issues.apache.org/jira/browse/SIS-73
Project: Spatial Information Systems
Issue Type: Task
Components: Utilities
Reporter: Martin Desruisseaux
Assignee: Martin Desruisseaux
Priority: Minor
Fix For: 0.3
For every UUID (_Unique Universal Identifier_) assigned to an
{{IdentifiedObject}}, SIS automatically keeps the association using weak
references in an internal map. This allow to retrieve the object by UUID if the
object is still alive in the JVM. The rational was that if UUID are truly
unique, then there is few risk of ID clash even if we use a system-wide map.
However this cause a number of risks:
* The "truly unique" hypothesis may not hold in practice. Consider for example
the case were the user reloads many times the same ISO 19139 document. If the
document contains an object with {{gco:uuid}} attribute, then the same UUID
will be assigned many times - admitely to equivalent objects, but the user
could have edited a previously loaded instance.
* In order to be truly effective, developers need to provide their own "UUID to
object" mapping anyway, because the universe of UUIDs is large and the
developers probably have some database for them. Our own management of "UUID
assigned in the current JVM" is likely to overlap with the developer's database.
Applying the prudential rule "_in case of doubt, leave it out_", the proposal
is to remove the automatic "UUIDs to objects" mapping, but keep this JIRA task
in the archive in order to make easier to find the Subversion revision number
to revert if this functionality is considered useful in a future SIS version.
As a minor side effect, the {{putIfAbsent}} method from {{WeakValueHashMap}}
should also be removed. It was added for supporting the feature documented in
this JIRA task at the cost of slight complication of implementation. Given that
{{WeakValueHashMap}} is not real concurrent map, we may be better to avoid any
{{ConcurrentMap}} method.
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