CollectionFactory should create empty EnumSets and EnumMaps [SPR-12533]

[spring-projects-issues]

Sam Brannen opened SPR-12533 and commented

Status Quo

#17089 introduced conversion support for EnumSet and EnumMap in CollectionFactory; however, the newly introduced support contradicts the existing contract for the related methods by creating a copy of the supplied set or map, thereby potentially including elements in the returned collection when the returned collection should in fact be empty.

Deliverables

1. Refactor createApproximateCollection() so that it returns an empty EnumSet.
2. Refactor createApproximateMap() so that it returns an empty EnumMap.

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Affects: 4.1.3

Issue Links:

• Default conversion support for EnumSet / EnumMap [SPR-12483] #17089 Default conversion support for EnumSet / EnumMap
• CollectionFactory API is not type-safe [SPR-12537] #17142 CollectionFactory API is not type-safe

Referenced from: commits aec284a

[spring-projects-issues]

Sam Brannen commented

Resolved as described in the comments for GitHub commit aec284a:

Create empty EnumSets & EnumMaps in CollectionFactory

#17089 introduced automatic type conversion support for EnumSet and
EnumMap. However, the corresponding changes in CollectionFactory
contradict the existing contract for the "create approximate" methods
by creating a copy of the supplied set or map, thereby potentially
including elements in the returned collection when the returned
collection should in fact be empty.

This commit addresses this issue by ensuring that the collections
returned by createApproximateCollection() and createApproximateMap()
are always empty.

Furthermore, this commit improves the Javadoc throughout the
CollectionFactory class.