On Apr 21, 2006, at 1:28 PM, Duong BaTien wrote:
Please see in-line comments:
On Fri, 2006-04-21 at 10:22 -0700, Jim Marino wrote:
On Apr 21, 2006, at 9:40 AM, Duong BaTien wrote:
On Fri, 2006-04-21 at 08:12 -0700, Jean-Sebastien Delfino wrote:
This came up on our April 19th IRC chat:
For our JavaOne release we are thinking about dropping the
Portable Web
Application integration approach (also discussed on this list as
Shallow
Integration).
We would only support the SCA Aware Container integration approach,
where we configure Tomcat with a custom Host implementation that
bootstraps the Tuscany runtime (aka Deep Integration).
What do people in the group thing about this direction? any
opinions?
1) I assume that this direct approach can still work with other
portable
approach plugins such as Jsf, Spring, Facelets, and Shale all
together?
I think the portable web container approach is something slightly
different (i.e. how to plug into a servlet container using generic
Servlet APIs). Spring and JSF would integrate using different
mechanisms. For spring, we are planning on using our extensibility
mechanism (we are working on that now and will post to the list as
progress is made). JSF should be rather straightforward. SCA local
services map 1:1 to JSF backing beans. There is some factory class
defined by JSF for integrating third-part containers as backing beans
hosts - I forget the class off the top of my head but this is how I
would approach it. Any contributions would be appreciated for this.
Spring has a nice integration with Jsf that we use for DI (except
session scope that we must use jsf)
org.springframework.web.context.ContextLoaderListener This enables the
mixing of Spring bean and Jsf. Please make sure that Tuscany, Jsf and
Spring can play well together.
I believe the approach I mentioned would achieve this using just JSF.
In this case, SCA components would be backing beans that were located
by the JSF factory I mentioned.
Also, BigBank has some examples of taglib integration that places
local services in a JSP page context (which can then be accessed by
JSP expressions).
I don't know much about Shale except that it is some kind of state
machine for UI components. Not knowing more detail, I probably would
do one of the following:
- just call SCA through ModuleContext.locate in whatever Shale uses
to handle incoming requests and dispatch to services. As long as the
SCA context is set prior to the Shale code is executed (this should
be automatic in Tomcat; in a generic J2EE container it would be a
matter of setting the proper order for Servlet filters).
- for a more complicated integration, I would look for a plug point
in shale that would allow one dispatch out to SCA local services to
handle incoming requests. This would be similar to JSF.
Shale is just an extension of Jsf and acts as an application
controller
org.apache.shale.faces.ShaleApplicationFilter to enable seveal
additional features at the UI side such as Dialog or remote for ajax.
Dialog is just a bean in user session to maintain UI state for
conversation longer than 1 request and less than 1 session. It is
popped
out of the session scope at Dialog exit point. Tuscany has module
scope
in addition to other standard scopes. It would be nice to have some
source of integration to maintain the flexibility of choice and well
integrated when used together i.e. co-ordination of state
management at
both the UI and backend processing.
Yes that is intended. There is a way to extend Tuscany ScopeContexts
which could be used to achieve this.
2) Does this approach mean that for every tomcat version, Tuscany
still
needs the way it is currently doing? Will the portable way be
supported
sometime after JavaOne?
Yes we intend to support the portable way. If you would like to
contribute (in order to have it sooner), we would be happy to help
with questions, etc.
Jim
It is good to hear this for the freedom of mix and match of selected
components and features. For contribution, let's see how it turns out
based on available time i can devote to it. There are 2 areas i am
intended to spend some time:
1) It is nice to turn SCA components into SCA/CoR components using
Apache commons-chain so chain features of commands/filters/chains
can be
part of the component assembly. If Ejb session bean is used as
business
logic, the beans can be assembled in both SCA and CoR (simple re-
usable
components without the need of BPEL).
I'm not sure where BPEL plays into this.
Our wire architecture can be used to do both one-way and around style
interception on an invocation so that may achieve some of what you
are looking for. I've also thought about the possibility of some
type of "instance construction" interceptor that would be invoked
when a component implementation is instantiated by the container. Do
you have specific use cases in mind?
For EJB, the SCA specification will be defining a standard
integration for that (i.e. the ability to wire to and from session
EJBs). I imagine this would be the approach Tuscany would look at.
Again, chain has its DI, but we
can wrap around and use Spring beans.
2) Ejb3 persistence is an important technology. Tuscany will be useful
with Ejb3 DAS. Apache OpenJPA is already there. Since entity bean
can be
Jsf backing bean, DTO is eliminated if all components are in the same
server.
Yes this is a good architecture for "traditional" web apps that
Tuscany should support. I think there are another set of web
applications (something like Ajax) where SDO may provide some of the
heavy lifting you mentioned in cases where DTOs are needed (i.e.
serialization to clients that manipulate data and send it back).
SCA/CoR business components will drive Jsf entity beans using
Ejb3 DAS.
Integrating with EJB3 persistence would be a good thing. If you are
interested in contributing, I could point you to some things that may
be helpful.
The framework does most of the heavy lifting;-)
Hope to hear more about these 2 areas.
BaTien
DBGROUPS
Thanks
BaTien
DBGROUPS
[snip]
Jeremy Boynes wrote:
There are two ways we can run as part of a web application:
1) Using pure J2EE APIs and running as a portable web application
2) Running as SCA module within an SCA aware web container
== Portable Web Application ==
In this mode we want to run as a self-contained application in a
stock
web container - all we can rely on are the J2EE APIs and that we
have
been granted sufficient privileges to run.
In this mode all classes need to be bundled with or made
available to
the web application - all JAR files will be included in WEB-INF/
lib or
WEB-INF/classes, made available as references to JARs in a
containing
EAR file, or added to the application classpath using some
container-specific mechanism.
Application isolation will make it difficult/impossible for
different
web applications to share information so each web application
will be a
standlone unit, either a subsystem with all module components
present in
the application or a single module component.
The runtime can be booted on application startup from
ServletContextListener. This listener will boot the runtime,
load the
system definition, and load the application modules. It can bind
the
system or module definitions as attributes in the ServletContext.
Each request needs to be associated with the module context
for the
invoked servlet (in the subsystem case different servlets could
map to
different module components). This can be done by a Filter that
binds
the appropriate ModuleContext to the Thread for use by
CurrentModuleContext.getContext().
Each web-service entry point must be bound so a web-service
endpoint,
which if we are using the Axis transport, done by configuring
the Axis
servlet. The configuration of the Axis engine can be built
during the
bootstrap above and passed to the servlet as a ServletContext
attribute.
Finally, session expiration needs to be detected and a
notification sent
to the runtime. This can be done using a HttpSessionListener and
may be
combinable with the ServletContextListener above.
All of this must be configured by the user in their web.xml file
- a
little configuration here being the price for portability across
container. Specifically, the following entries must be added:
* A <listener> configured to boot the runtime
* A <filter> configured for the request filter
* A <filter-mapping> for each path associated with a module
* A <servlet> for the axis servlet
* A <servlet-mapping> for the axis servlet
* A <listener> for session expiration (if not combined)
In this configuration, RuntimeContext is a non-priviledged API
(it runs
with the permissions of application) but although it is exposed
for use
by these infrastructure artifacts there is still no need for the
application to use it. We can't stop application code from doing
so but
this is not harmful as everything is running with application-
level
permissions.
== SCA Aware Container ==
To avoid the need for users to explicitly configure their web
applications to enable SCA, we may be able to integrate the
runtime
directly with the web container. In this mode, the runtime would
run as
a privileged extension to the container and would automatically
configure the SCA environment for a deployed web application. We
have
started to do this with Apache Tomcat.
All classes for the runtime would be placed in the appropriate
location
for the container (e.g. Tomcat's server/lib) and would not be
exposed to
the application. The only access the application would have
would be via
the standard SCA APIs.
The runtime would bootstrap with the container, before any
applications
were deployed. How this is configured is container-specific -
with the
current Tomcat integration we have a specialized implementation
of Host
that is activated by specifying the appropriate class name in
server.xml
When an application is deployed, the container extension detects
this,
inspects the application to see if it requires SCA and if so
configures
the container as necessary. The user only place the sca.module
file in
the application for this to happen - there are no SCA-specific
entires
in web.xml
The container will need to configure the same sort of entry-
points as
described above but may do so in container-specific ways. For
example,
the Tomcat integration adds a Valve to the processing pipeline
instead
of a Filter as a Valve has access to internals that a Filter
does not
(for example, it is able to attach notes to the request).
For web-services, the extension code needs to examine the SCA
module and
make sure all the entry-points are bound. One way it could do
this is to
configure a single Axis servlet with a engine configuration that
maps
each request to the appropriate entry-point; another is to
define a
separate servlet (or internal equivalent e.g. in Tomcat's case a
custom
Wrapper) for each entry-point that is attached directly to the
entry
point's context in the runtime.
In this type of configuration, the RuntimeContext is a
privileged API
which should not be (and does not need to be) exposed to the
application.
--
Jeremy
[snip]
