how serializable is releated to caching a java/command class?

Question

I am working on ibm websphere commerce (wcs). In this framework we have an option to cache our command class, basically they are just a java classes. While having a new cache entry i got to know that these java classes must be serializable (implement the java.io.Serializable interface). Why is that?

is it like caching is basically saving an output of some execution? and in this case it will save the sequence of bytes generated as part of serialization and whenever a requested to that cached object comes then it will just deserialize and returns the object without executing actual program? Can anyone please share knowledge about this??

Thanks in advance, Santosh

gkamal · Accepted Answer · 2012-06-28T19:00:08.677

For caching the result of a method execution and returning it for subsequent calls serialization is not needed.

The most likely reason it needs to be Serializable is that when you cache some data in a clustered environment changes made to the cached data on one node would have to be replicated on other nodes of the cluster. For doing this replication the data needs to be serialized and sent across to another node using some remoting api.

The other reason for requiring the class to be serialiazable is that the cache implementation might overflow the data to a disk. Even in this case the objects in the cache need to be converted to some form that can be stored on the disk and recreated.

The following is a passage from ehcache documentation that explains the overflow scenario in more detail.

When an element is added to a cache and it goes beyond its maximum memory size, an existing element is either deleted, if overflowToDisk is false, or evaluated for spooling to disk, if overflowToDisk is true.

In the latter case, a check for expiry is carried out. If it is expired it is deleted; if not it is spooled. The eviction of an item from the memory store is based on the 'MemoryStoreEvictionPolicy' setting specified in the configuration file.

Thanks for your reply. Can you please explain the second point in your answer? i din't understand how overflow of data will be controlled with the help of serialization? — Santosh Sidnal, Jun 27 '12 at 18:32

score 0 · Answer 2 · answered Jun 27 '12 at 13:37

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Serialization saves the actual object itself, in its current state.

answered Jun 27 '12 at 13:37

user207421

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score 0 · Answer 3 · answered Feb 26 '13 at 00:54

The reason why is due to WebSphere Commerce's use of WebSphere Application Server's Dynacache feature. WAS dynacache is an in-memory java cache that is very similiar to a built in memcached. Out of the box, the starter store uses the dynacache to cache JSP, servlets, controllers, commands, command tasks and other java objects. There is also caching done on the DB side. This is why in performance tests, IBM scales much better at high volumes than other software.

how serializable is releated to caching a java/command class?

3 Answers3