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Running a Java Web Start application without Java Web Start

I want to run a fat client delivered as a Java web start application without Java web start. I launched it via javaws and managed to get all the jar files mentioned in the JNLP file from the cache after they were downloaded.
I tried running the jar file that contains the main class according to the JNLP file, but I get the 'Could not find or load main class' error. Were I just trying to run a class I'd set the classpath accordingly, but since I'm running a jar file with java -jar, as far as I know the classpath settings will be ignored anyway. Now I'm not sure what to do, does anybody know how to tackle this?

I'll answer this myself now, turns out it is stupidly simple: Get all the jar files, unzip them to get the content, merge all the content (best done with rsync), create a new MANIFEST.MF file that contains the main class to be loaded and the merged hashes for all existing files from all MANIFEST.MF files, zip again to create a jar. That's it.

Java app deployment and updating in a Remove Desktop Services environment

I have a Java app which needs to be used in a Remote Desktop Services environment.
As the javaw.exe process holds a file handle of the JAR file, I can not replace the JAR as long as other users are working with it.
I can also not see the current users as there might be many other javaw.exe processes for other JAR files running on the same server. And in a server farm I would have to check every single server for open instances.
Is there a best practice to deploy and update Java apps in this environment?
Some ideas:
use a launcher app which has a configuration file which specifies the location of the JAR file
modify the entry in the start menu to point to the new JAR file location
copy the jar to a user-specific work folder on logon
use JWS
Option 3 and 4 however would mean that Log4J output needs to be directed to a location in a folder which can be accessed by operations / developers

Is there a way to get the application directory in Java?

This likely isn't possible, but I thought I would ask just to be sure. I have a batch file which starts my java app using relative paths. Ie. i have:
Application\start.bat
Application\lib*.jar
My application creates a configuration file in the Application directory. My batch script uses relative paths to point to the lib directory jars. This has worked really well for me because I can move the program wherever I want and it will just run. However now I would like to be able to call the same app from command line as well not just from a shortcut which has the working directory set to Application. The problem is that I want to be able to call my application from any directory on the command line and right now this doesn't work because the working directory will be different.
I know I can always add another parameter to my app for the working directory but then I still have to create a batch script with a hard coded path to my application. Is there any way around this in Java, for example to get the directory that my main java file is in on top of the working directory? Is there a launcher app perhaps?
I can't bundle my app as a jar because it creates configuration files which I want to be in the same directory as the application.

Consider just changing current dir in start.bat:
#cd /d %~dp0
java ...
This would change it to the folder where script is located.
pushd/popd commands can also be used to preserve current dir for calling script if needed.
Alternatively getClass().getProtectionDomain().getCodeSource().getLocation() can be used from java to get path to jar/classes.
There is also path-independent approach with config path system property:
java "-DconfigDir=%~dp0" ...

There is no portable solution that is going to work in all cases. Indeed, the notion of an application directory does not necessarily make sense; e.g. consider applets and applications launched using WebStart.
If the notion of an application or installation directory does make sense, then the simplest way to support it is to have the application's launcher / launch script pass it to the application Java code via an application specific -D property.

why doesn't my jar file run outside netbeans?

I built a jar file that can run perfectly within netbeans when I click run,
but when I try to run the jar file by double clicking it it does not run, nothing happens..

Double-clicking the jar starts it, but unless you have a GUI application that opens a new window (in a different thread), it most likely finishes and closes before you can see anything.
In these cases you normally run the jar from the console (java -jar ..) to see if there are any exceptions/errors.

Starting an application from the command line would let you debug the problem as Bozho said. But you need to check if you have all the files in dist folder that you need to run your program. For example if you are using a database file to get the data, you need to place this file in the dist folder after program is built. I think the jar file is using a relative path when looking for files.

Add files in jar during runtime

Project is to create exe file. If we run exe file it will open one admin page (designed in Swing) that page contains browse button, max install, max install sys, and create build, while click the browse button we need to select one exe file from system and that file need to save it inside one folder of jar file. The maxinstall, max install sys value is stored in SQL lite database. This admin page will open for first time only,to get condition from admin. Next if we run the exe file it must check maxinstall and all parameter and then install that selected exe file.
My problem is, I created jar from my java program. While running the jar each time, the admin page only opening (i.e) the database file is not updated inside jar, but its works fine in eclipse. After that I need to create jar to exe.

..it is possible to extract jar in runtime,addfile in the extracted jar and create a new jar in runtime..?
Most JREs will place a file lock on the Jars. Therefore they cannot be updated while the JRE is running. Check a sub-directory of user.home for an altered version of the resource. If it is not found, use the one in the Jar. If it is altered, save the changed data to the sub-dir.
Use a sub-directory based on the package name of the main class, to help avoid overwriting the resources of another app. (or other apps. over-writing your resources).

I think that I understand your problem. Your application stores its state into its own jar file. the fact that you are using SQLite etc. does not matter. It works from Eclipse because in this case the class files and resources are not packaged into archive and your program changes files on file system easily.
The answer is: yes, you can change jar file programmatically. Jar is just a zip. You can use ZipInputStream, ZipOutputStream, JarInputStream, JarOutputStream to modify any zip including your own.
But it is very very not recommended for too many reasons. The right solution is to separate your data from your application. You have to store runtime data on file system, DB etc. For example you can create files in user home directory. It is platform independent. You can also use Preferences class that has portable implementations for all platforms.
Yet another reason to do this is your requirement to create exe. OK, you can change jar file but once you created exe file from your jar you cannot change it anymore.

Once an executable .jar is created it will be "locked". I you add more files to a locked .jar, those files will not be recognized internally by the .jar itself at runtime. So, the better approach is to extract your dependent .jar and then add it to a new, executible .jar containing the new file(s) that you need. Then moving forward you can run this new .jar.