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Ok..I
have solved my problem. I added a little bit to my MVC framework to handle
web-app context forwarding.
As for
your questions, you can use JNDI to share data between app servers. How exactly,
I don't know..I read or someone told me that it can be done. EJB's are done in
this manner, and I'd imagine you can do it from servlets. I don't have the
API in front of me, but look to see if there is a setAttribute() or something
for JNDI. I think the Context or InitialContext classes have these methods.
Other than that, each web-app has its own "memory" space in a single JVM. J2EE
allows one (or more) EAR files to run in one application server on one JVM, and
in each EAR file you can have one (or more) web apps running (and EJBs, etc).
Each EAR I believe is a completely separate application, and each web-app in
that ear is separate from other web-apps in that ear or in other ears deployed
in the same JVM. Again, I think JNDI and perhaps the JVM Context are the only
ways to share data between apps running in the same JVM. Although, if your
working in a clusterable environment, I wouldn't program your app to expect data
from within the same JVM. EJB 2.0 has added "local" EJBs so that if the app
server sees the EJB being retrieved is in the same JVM, it can return a local
reference and avoid the network hit.
As for
deploying in one app server..I think that depends. First, what is your hardware
limit? Second, does it make sense to deploy them in one server? For example, in
my case, I am deploying 3 separate but somewhat related web-apps. It needs to be
possible that a link from one web-app can traverse into another web-app.
Therefore, it is absolutely required for me to deploy the 3 web-apps in the same
container. Each can be clustered as needed. Infact, I only need to cluster the
/inside web-app, as its the only one that really uses the session state. The
/outside is mostly static, and the /admin is related to internal employees that
is not necessary to cluster. Infact, the /admin site can run completely on
its own, but I can provide a connector from my /inside site to the /admin site
should the logged in user have the right priveleges to access
it.
HTH.
Can
you point me to where the spec talks about sharing data between
web-apps. We are dealing with some of the same issues also. I
didnt dig deep enough into the spec but was under the impression that
there was ways to pass the data between apps. I may be completely
wrong. What about between appservers?
Is
it a good idea generally to try to deploy all your web-apps in one appserver
or should you use multiple (instances) of the appservers. I guess this
is really more of a J2EE question than an orion question .... but
maybe someone wants to give it a whirl.
Thanks.
Casey Helbling
Hi
all,
Deploying 3 web-apps in one application in Orion; Outside, Inside and
Admin. Outside is mostly static, with a login section. The login section
takes the user to the Inside app by calling
into it via a /inside/Login.do?command=Login (using the popular Struts MVC
syntax). This all works. Using
Struts MVC (and even with my own), it appears that when trying to forward to
a different web-app context, its not possible. At least not yet..could be my
code. In MVC, the ControllerServlet running in one context, tries to forward
to a resource. Almost always this is in the same servlet-context (web-app)
as the ControllerServlet. In my case, I want a user to log out, which takes
them to the outside index.jsp page again. The normal RequestDispatcher() is
part of the Inside web-app context, so when it tries to forward to a
/index.jsp, I would think the / would indicate the context to forward to.
This doesn't appear to work. So then I tried using the
ServletContext.getContext(url) call where the url is the same as the
forwarding resource. Thus, to forward from any web-app to the outside "root"
index.jsp page, I do something like:
getServletContext().getContext("/index.jsp").getRequestDispatcher("/index.jsp").forward(request,
response); This gets the right ServletContext of the root app. I have
tested this by creating an object and setting it as an attribute in the
/index.jsp, and in the ControllerServlet I get the ServletContext and look
up the attribute (before trying to forward), and it finds it. So when using
that ServletContext and trying to forward, its still not finding the page. I
continue to get 404 not found
errors.
My
question is..is it possible to forward from one web-app to another? It
appears to work when I go from the / to the /inside context just fine (at
least it appears that on the JSP page using a href or form action url path
of /inside/Action.do, it does work by calling into the /inside web-app). I
can't imagine that deploying multiple web-apps limits you to not even
forwarding to another web-app. I do know you can't share any data between
web-apps, but being able to jump from one web-app to another via links and
via forwarding should work..shouldn't it? The API isn't exactly clear on
this..but I will look at it again.
Thanks.
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