Static variable in session bean

From a Java language perspective, nothing stops you from declaring a static variable in a session

bean class.It will compile as long as its syntactically correct.

From an EJB programming model perspective, the use of *non-final* static variables

is discouraged because it breaks the JVM-transparency that is an important aspect of the

EJB architecture.It should be possible to deploy a single EJB application to a cluster and

have it behave exactly as if it were deployed to only one server instance (albeit with higher

overall throughput/performance).Using non-final static variables breaks this property

because the bean instances in one JVM will see a different value for the static variable

than bean instances in a different JVM.

It also forces you to deal with synchronization

of the shared data, which is a complexity that was carefully avoided in the EJB programming

model by ensuring that each bean instance is single-threaded.

Bottom line is you can have "final static" data members in EJB classes but you should

avoid non-final (mutable) static data.

--ken

ksaksa at 2007-7-9 20:47:34 >