Hacker News new | ask | show | jobs
by greyboy 4649 days ago
Interesting about keeping a JVM running for compilation. I'm curious about doing just this for my day job but can't seem to find a good explanation. Do you have any resources to point me to?
2 comments
jared314 4649 days ago
For a persistent JVM, take a look at Nailgun [1].

Additionally, the Drip project [2] uses a swapping strategy, by keeping an additional JVM spun up in the background. It was apparently built because the authors had trouble with persistent JVMs containing old dependencies.

[1] http://www.martiansoftware.com/nailgun/

[2] https://github.com/flatland/drip

link
6ren 4649 days ago
javac is itself written in java, so you can write a little program that does that in a loop, waiting for some trigger. I actually just had it in a shell, waiting for you to hit return, which also called my code after compilation.

An unexpected benefit (unexpected to me, anyway) was that not only do you avoid the startup penalty, but you also benefit from JIT compilation of javac itself - every time it compiles, it gets faster! IIRC it's fairly substantial the first 10 times, but still improving at 50.

Here's a working minimal starting point I just put together for you (check docs, google, stackoverflow etc):

  import javax.tools.*;
  import java.io.*;

  class Demo {
    public static void main(String args[]) throws IOException {
      JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
      int result = compiler.run(null, System.out, System.out, args);
    }
  }

 java Demo Foo.java     # compiles Foo.java
Here's a stackoverflow answer suggesting something similar http://stackoverflow.com/a/793913/50979

BTW: I called out to a bash script to work out which source files had changed, because it's easier than writing that bit in java (and this compiler doesn't do that for you - it just compiles the explicitly listed source files).

HTH - let me know if you need more info. I've been thinking of using Jnotify to watch for source files being written to, so it's 100% automatic - one issue is that I save quite often, and each will trigger a compile (I'm doing this with plain javac and inotify at the moment).

link