Same applies for me = not sure I understand the question.
But in principle for using GetElementById, create a B4J Server App with a WebSocket. GetElementById is described
here, for that.
An example project download
here = WebApp adding a button Dynamically.
Note:
- You do not need Apache to be setup on the Raspberry Pi, as B4J Servers run autarkic = just run java -jar yourapp.jar, then access via browser with HostAddress : Port. In the latest Raspian versions, Java is by default installed.
- B4J Server Apps run very well on Raspberry Pi's (based on my experience so far with several apps running for monthes on various Pi's)