How do you remotely update Java applications?

Question

We\'ve got a Java server application that runs on a number of computers, all connected to the Internet, some behind firewalls. We need to remotely update the JAR files and start

Answer 1

Jars cannot be modified while the JVM is running on top of it and will result in errors. I have tried similar tasks and the best I came up with is making a copy of the updated Jar and transition the start up script to look at that Jar. Once you have the updated Jar, start it up and wait on the old Jar to end after giving it the signal to do so. Unfortunately this means a loss of GUI etc. for a sec but serializing most of the structures in java is easy and the current GUI could be transferred to the updated application before actually closing (some things may not be serializable though!).