Reimplementation of
OFBizPropertySet that caches property entries and values to provide
more efficient access.
Note that
JiraCachingPropertySet is just a decorator around an arbitrary supplied
property set and thus has uncertain behaviour both in a clustered environment and when there
are multiple instances of the caching property set, as the individual caches have no way to
share state.
CachingOfBizPropertySet is different. It is a flyweight around the
OfBizPropertyEntryStore, which caches the operations that it can (such as the
existence, type, and value of an entry) and delegates those it can't cache to the database
directly. The implementation deviates from that of
OFBizPropertySet only in ways
that make it more fault-tolerant, such as by not throwing an exception when removing a
nonexistent property and not throwing an exception when setting a property to a new type
without removing it first.
The only known disadvantage to using this class is that it will eagerly load the value on
a cache miss. This seems to be an acceptable loss, because the main reasons why code
would bother to call
#exists(String) or
#getType(String) seem to be
- To know whether or not the property exists and/or the appropriate getter type to use,
both of which suggest that the value will eventually be retrieved anyway and that
loading it eagerly is not wasteful.
- To guard against the exception that
OFBizPropertySet throws if you attempt
to remove a property that does not exist of change the type of an existing property.
This implementation silently ignores a spurious remove and gracefully updates the type
if it is changed, so these guards are not necessary.
- To use the existence or absence of the key as a
boolean value, where the actual
stored value is a meaningless sentinel. This is a strange thing to do, and it makes
more sense to store an actual
boolean value for the property, instead.
This class is thread-safe, in spite of the difficulties that the
PropertySetcontract imposes upon it. Its only mutable state is the entity definition provided through
PropertySet#init(Map,Map). This is stored in an immutable holder class whose reference
is marked as
volatile to ensure safe publishing.
Although
OFBizPropertySet itself allows for multiple generic delegators to be used,
this implementation ignores this setting. JIRA always uses the
"default" delegator.