How to run the dynamic jnlp generate by jsp, but cache one is not dynamic?

Question

Hi Web Start expert,
I need some urgent help on this issue. I want to pass some session info from my protal web app to my java app through web start. I have tried to use a servlet or jsp to generate a dynamic JNLP which will include all the necessary properties. It works fine if I don't include a href attribute in my jnlp tag. but I won't be able to launch the application off line. So I include the href to point to a static jnlp file resides in the same directory where jars are installed. This time when web start launches, my Java application does not seem to recognize all the login properties I passed through web application, and launch the Login Dialog. What I want to do is, if I come from the portal, since I had signed on to the portal, I don't need to login again to the java app. but when next time I click on the offline shortcut on my desktop for my Java app, I need to sign on to launch my Java app that was cached on the client machine. What is the best way to do this? Please help!
Thanks in advance.
Jenny

Answer 1

The problem here is, when you acess the servlet from the browser, the servlet generates the jnlp file with the properties based on the full reference to the servelt (ie: http://myhost.com/servlet?arguments=xxx;yyy).
If you put the href in the jnlp file:
<jnlp codebase="http://myhost.com" href="servlet">, When Java Web Start is invoked, it will re-download the jnlp file using just "http://myhost.com/servlet", This will cause the servlet to generate jnlp file w/o the propertys that were based on the arguments and parameters to the url.
On the other hand, if you try to add the arguments and parameters to the href wirh <jnlp codebase="http://myhost.com" href="servlet?arguments=xxx;yyy"> two problems occur.
1.) java web start (all versions thru 1.4.2) will generate the cache directory based on the whole string "servlet?arguments=xxx;yyy" this means that every invocation is a seperately cached app, and you will get lots of entries in the download applications page in the Application Manager.
2.) on some platforms, generating cache directory with "?" or ";" can cause IOExceptions.
These problems will be addressed in 1.5:
1 - the cache directory will be based only on the string up to the first "?" or ";".
2 - jnlp files w/o href, will still be shown in the downloaded applications, and can be launched offline (if offline-allowed)
In the mean time the only work around I have heard, is someone tried modifying the servlet, to first download the jnlp file with the correct parameters and args but with href="servlet", but caching the jnlp file generated, and then when java web start requested the servlet with no args, a few seconds later, sending it back the cached version.
/Dietz