On Jun 16, 2008, at 11:14 AM, Dain Sundstrom wrote:
On Jun 13, 2008, at 1:12 PM, Karsten Ohme wrote:
Hi,
Maybe a very simple question, but I haven't found a solution:
Is it possible to store any data in the SessionContext of a Session
Bean?
Unfortunately, no. The session context is a read only object.
I have a stateless bean which executes a method. In this method
exceptions can be thrown and some critical data is touched. This
data cannot be kept in the persistence layer and rolled back
automatically in the case of an exception (performance reasons and
parallel execution does not allow this). So I have to keep manually
track of this data and roll it back manually. This method is used
in a chain of other services and if any of these services fail, the
rollback must take place. This is the reason I cannot catch it in
the method itself. So there is an interceptor which is placed in
the upper facade implementation which starts the service chain. In
this interceptor I catch all exception, want to read the data, roll
it back and throw the exception. But how to get hold of the data
here?
A stateless bean is shared amongst multiple callers, but only one
caller will have access to the bean at a time. This means that a
stateless bean isn't well suited for storing state. The stateful
session bean was specifically designed to store state in it's
fields. The session bean can be notified of the transaction begin
and completion (commit or rollback), but rollback of the changes to
fields, it the responsibility of the listener code (which is a nice
way of saying you have to do it manually).
Note that stateless beans are fine places for thread locals and statics.
Another API that might be useful is the
javax.interceptor.InvocationContext.getContextData() Map. You're
allowed to get/set anything you like in that map and it will live for
the life of the invocation. Interceptors can pass each other data
this way. As well via the InvocationContext.getTarget() method you
can get the bean instance itself that will be invoked. Any number of
interceptors can call methods directly on the bean instance, so you
can expose any number of bean class methods directly to the
interceptor that you don't have to even add to your business
interface. It's possible to use interceptors to inject data into the
bean instance before an invoke or pull data out of the bean after an
invoke, or other similar things.
-David
