[SHIRO-566] CollectionUtils should use Collections wrappers of arrays if possible

• Type: Improvement
• Status: Resolved
• Priority: Trivial
• Resolution: Fixed
• Affects Version/s: 1.2.4
• Fix Version/s: 1.3.0
• Component/s: Authorization (access control)
• Environment: Any
• Assignee: Unassigned
• Reporter: Matt Bishop
• Created: 30/May/16 17:44
• Updated: 29/Jun/16 22:21
• Resolved: 29/Jun/16 22:21

Description

org.apache.shiro.util.CollectionUtils.asSet() and .asList() could use Collections wrappers for the passed-in elements. These are smaller and faster than copying the contents into other collections.

The editability of the returned Collections is not required as currently it will return either an unmodifiable emptyList() / emptySet() or a modifiable ArrayList / LinkedHashSet. Ideally it would wrap the LinkedHashSet in unmodifiableSet and declare the immutability of the returned collections in the docs.

In my use case for Shiro we create about 6000 - 7000 WildcardPermission objects per second. The great majority of them have a a list of parts with single subparts and thus don't need a proper LinkedHashSet created. This change improve the performance of our system by 10% under heavy load, mostly due to the reduced GC of temporary LinkedHashSet objects.

Issue Links

• links to: GitHub Pull Request #19