Updating a running JAR file without using JDK

Question

Hi guys, I have been stuck on this problem for days. I have a program that allows the user to log in and encrypt/decrypt files. This program must be stored on the removable drive and it should work on any operating system without requiring any installation of files. In order to store their login data, I wrote it to a shadow.txt file. My idea was to pack this shadow file into the JAR file so as not to create unnecessary files. I understand that in order to update JAR files, all I need to do is to do
Runtime.getRuntime().exec("jar uf login.jar shadow.txt");However, here's the problem. I cannot assume that every user PC has JDK installed. As JRE doesn't have jar.exe, that command won't work anymore. Furthermore, the JAR is currently in use. So even if the user has JDK, windows will never allow this command to go through. Anyone has any ideas?

Answer 1

I had similar requirement, except that, i used a war file.
Had a client.war file in JBoss deploy directory, and i needed to update client.jnlp file present in it.
But as jar.exe comes only with jdk, could not use jar -uf command.
But not sure if it works with other application server too,
in jboss we can explode the war file, meaning we can create a directory "client.war" in deploy directory and extract your client.war contents to it. Now when server starts, it considers the extracted directory as web archive application.
This extraction can be done with out using jar.exe. can be done using jarinputstream aswell.
Once the contents are extracted , the files in it can be modified with out jar.exe.
For my case it worked as my client.war file is not signed, although the resources inside are signed.