That would work. Sometimes, you?re not allowed to check system properties
inside an app server though. Another approach would be to call
System.exit(1) if you find out that they?re not running a 1.4+ JVM. Then,
if that happens enough times, maybe they?ll go ahead and upgrade the server
to a 1.4+ JVM in hopes of fixing the problem! :-)
-----Original Message-----
From: Herbers, Joe [mailto:herbers@xxxxxxx]
Sent: Wednesday, September 01, 2004 4:32 PM
To: users@xxxxxxxxxx
Subject: RE: [cinjug-users] WebApps: how not to deploy?
-->
Another option that I meant to mention is having the jsps that are hit
initially (probably only one in our case), do a check for JDK 1.4 (assuming
there?s a decent, inexpensive way to do this ? check a system property?) If
the appserver is not running 1.4, then send a meaningful message to the
client that the app requires 1.4 (contact your administrator, whatever)
This doesn?t address finding out before the first client hits the
appserver. But anyone deploying the war will at least connect to the app
once, at which time they will see a nice clear message in their browser, not
buried in some appserver log file, or scrolled off the window where some
appservers display stdout.
What do you think about the two approaches? How about both? You could do
the jsp message for the user and also have a servlet init check the jdk
version (via system property?) and print a message if it fails, with or
without throwing ServletException (if your jsp can run without the servlet
in place).
From: Herbers, Joe [mailto:herbers@xxxxxxx]
Sent: Wednesday, September 01, 2004 3:48 PM
To: users@xxxxxxxxxx
Subject: [cinjug-users] WebApps: how not to deploy?
Let?s say you have a web application that requires Java 1.4. Is there a
good way to prevent it from deploying on an appserver if the appserver is
only running 1.3?
What I?ve noticed by default on at least one appserver is that you won?t see
an issue till a client hits a JSP page that references a class file, at
which point the client gets a message like ?The major.minor version '48.0'
is too recent for this tool to understand.?
This isn?t very clear! Rather than this appearing to the first user who
hits the server, we?re thinking perhaps it would be better to print an error
message on startup. However, since the output may be buried in a log file
somewhere (for example on Oracle 9i?s AppServer) it seems like the only way
to get attention is to prevent deployment of the war as well. What do you
think?
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