Re: [Springframework-developer] Are there scenarios where EJB is a better option than Spring?

[Juergen H. <ju...@in...>]

Spring Remoting and Remote EJBs are quite different solutions to the =
same
problem - actually, different in style more than different in =
capability.

Spring Remoting follows the philosophy of taking existing POJO service
instances and exporting them under a given protocol, at a given URL, =
with
configurable protocol. Exporting the same service instance with =
different
protocols *at the same time* is straightforward: simply define multiple
exporters at different URLs, with each exporter pointing to the same =
service
but talking a different protocol. The target service instance can be any
existing application service, as long as it's suitable for remoting =
(i.e.
has serializable arguments etc).

The supported protocols include Hessian, Burlap, HTTP invoker, =
traditional
RMI and RMI invoker - both using any RMI protocol internally, be it =
JRMP,
IIOP or WebLogic's T3. Furthermore, there's also support for Web =
Services
via a JAX-RPC provider (such as Axis). The only environment required is =
a
plain Servlet container, or even just a plain JVM in the case of RMI. No
special class loaders get created; Spring's remoting seamlessly nestes =
into
an existing environment, exporting existing local application services =
where
needed.

Remote EJBs on the other hand are based on the explicit notion of a =
remote
component that you have to implement based on a strict component model. =
Such
a component then gets deployed; binding it do a specific protocol and =
URL is
part of the (partly server-specific) deployment step. Binding to =
multiple
protocols at the same time means deploying your Remote EJB multiple =
times,
with different EJB instances representing each deployment.

Of course, remote EJBs just work within an explicit EJB container, based =
on
a specific deployment unit and running in their own class loader. EJBs =
get
deployed separately; they are effectively not plain remote service =
facades
but rather fully self-contained application components that natively =
have a
remote service interface. EJBs are not made for exposing some existing
application service but rather for building self-contained remote =
services.

So the main difference is essentially the configuration and deployment
model. If all you want is export some remote services from an existing
application, take Spring Remoting, in particular if the existing =
application
is a WAR file or a standalone application (running outside of a J2EE
server). If you want to build self-contained remote components that you =
can
deploy on their own and that are not an inherent part of an overall
application, take remote EJBs.

Remote EJBs also offer stateful remoting as a central part of the =
component
model, while Spring Remoting is primarily about stateless remoting - =
just
like Web Services are stateless. So if you have a strong need for remote
sessions, remote stateful session EJBs are a straightforward solution.
However, double-check whether you actually need stateful remote =
sessions;
stateless remoting is inherently much more scalable.

A further advanced feature of remote EJBs is remote transaction =
propagation,
that is, a client-side transaction getting propagated to remote =
services.
This is in most cases architecturally undesirable, though, and not =
generally
supported by all J2EE servers. If you really need this feature, you =
could
also consider using Spring's RMI support in conjunction with your J2EE
server's RMI subsystem: for example, with WebLogic RMI, which offers
seamless propagation of the transaction and security context.

Juergen


-----Original Message-----
From: spr...@li...
[mailto:spr...@li...] On Behalf =
Of
Garvey, Paul M (GE Commercial Finance)
Sent: Friday, November 04, 2005 2:03 PM
To: spr...@li...
Subject: RE: [Springframework-developer] Are there scenarios where EJB =
is a
better option than Spring?

=20

Yes, I was actually on page 9 :-) Anyway, thx

On page 11 of "Expert One-On-One J2EE Development without EJB" it States
that EJBs is the best solutions for application that need object
distributed.
Why is this a better solution than Spring Remoting? Is it the the EJB
container provides Better support for distribution than Spring?


-----Original Message-----
From: spr...@li...
[mailto:spr...@li...] On Behalf =
Of
James Cook
Sent: Thursday, November 03, 2005 2:51 PM
To: spr...@li...
Subject: RE: [Springframework-developer] Are there scenarios where EJB =
is a
better option than Spring?

You must be in the single digits of your reading! :-)

Try Page 11, "Should We Ever Use EJB?"


-----Original Message-----
From: spr...@li...
[mailto:spr...@li...] On Behalf =
Of
Garvey, Paul M (GE Commercial Finance)
Sent: Thursday, November 03, 2005 10:19 AM
To: spr...@li...
Subject: [Springframework-developer] Are there scenarios where EJB is a
better option than Spring?


All,
I am fairly new to Spring and I have started reading "Expert One-On-One =
J2EE
Development without EJB"=20
1.=A0=A0=A0=A0=A0 I am trying to find senarios where EJB is a better =
option
=A0=A0=A0=A0=A0=A0=A0 than Spring but so far I haven't found any in the =
book.=20
=A0=A0=A0=A0=A0 Just started reading BTW.=20
2.=A0=A0 =A0=A0 What are some of the weaknesses of Spring? The =
weasknesses
=A0=A0=A0=A0=A0 of EJB is well documented by the book.=20
BTW, very good book, I intend to read it in its entirety.=20

- Paul=20




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