Dynamic update of java program launch

Question

For new software, we are currently evaluating ways to update software.

Basically, the software is a tiny graphical application written in Java that interacts with the server and often runs 24x7.

The requirements for updating the program are as follows:

• Check for updates at startup
• Check for updates and dynamically update them during operation (at the request of the user, periodically or initiate from the server)

Current Results:

• JWS is designed to download and install applications at startup and has some well-known limitations.
• Install4j is much more than we need and therefore too complicated for our application.
• Getdown? Not sure if you can dynamically check for updates at startup

Are there other ways to meet the requirements? Is it possible to achieve using getdown (I have not found a lot of documentation on this topic)?

Thanks in advance for the helpful answers.