Re: [javagroups-users] ReplicatedHashMap question

[Bela B. <be...@ya...>]

Ahrens, Richard (Equity Linked Technology) wrote:
> Since ReplicatedHashMap in jgroups-2.5.0 extends HashMap and none of 
> its methods are synchronized, is there a way to prevent a 
> ConcurrentModificationException if the application code is reading or 
> writing to the map at the same time a JGroups thread is invoking 
> _put(), _remove(), etc.?

No, not by default. ReplicatedHashMap has the same semantics as HashMap, 
which is unsynchronized. However, since RHM delegates all calls to its 
super class, you could do

ReplicatedHashMap rhm=...;
Map map=Collections.synchronizedMap(rhm);

and access the RHM only through 'map'. This should work, as even 
replicator methods such as _put(), _clear() etc delegate to HashMap's 
put(), clear() and so on, and these will be synchronized.

Note that ReplicatedHashMap is quite simple with respect to 
functionality. If you want locking, cache loading etc, I recommend 
JBossCache.
Cheers,

-- 
Bela Ban
Lead JGroups / JBoss Clustering team
JBoss - a division of Red Hat