Shameless plug: this seems like a good application for Doppio: https://github.com/int3/doppio https://github.com/int3/doppio The whole JVM lives in the browser

Shameless plug: this seems like a good application for Doppio: https://github.com/int3/doppio https://github.com/int3/doppio The whole JVM lives in the browser, so you don't need to rely on hacks to "sanitize" user programs.