Run SBT 1.2.8 project with Java -D options on Windows

Question

I have been running my Play projects using the deprecated Activator wrapper for SBT, and it allows me to specify -D options for the JVM it launches like so:

> activator -Dhttp.port=9000 -Dplay.server.websocket.frame.maxLength=10485760 "run 9000"

This is very useful as it allows me to create separate .bat files for running a given project on different ports, which is great as I'm working on several different websites in parallel.

However, I've been unable to transition this command line to use SBT directly:

> sbt -Dhttp.port=9000 -Dplay.server.websocket.frame.maxLength=10485760 "run 9000"
...
[error] Expected letter
[error] Expected symbol
[error] Expected '+'
[error] Expected '++'
[error] Expected 'java++'
[error] Expected 'java+'
[error] Expected '^'
[error] Expected '^^'
[error] Expected '+-'
[error] Expected 'debug'
[error] Expected 'info'
[error] Expected 'warn'
[error] Expected 'error'
[error] Expected 'addPluginSbtFile'
[error] Expected 'show'
[error] Expected 'all'
[error] Expected 'Global'
[error] Expected '*'
[error] Expected 'Zero'
[error] Expected 'ThisBuild'
[error] Expected 'ProjectRef('
[error] Expected '{'
[error] Expected project ID
[error] Expected configuration
[error] Expected configuration ident
[error] Expected key
[error] Expected end of input.
[error] Expected ';'
[error] Expected 'early('
[error] Expected '-'
[error] Expected '--'
[error] Expected '!'
[error] .port
[error] ^

Adding -J as suggested by https://stackoverflow.com/a/47914062/708381

> sbt -J-Dhttp.port=9000 -J-Dplay.server.websocket.frame.maxLength=10485760 "run 9000"
...
[error] Expected symbol
[error] Not a valid command: -
[error] Expected end of input.
[error] Expected '--'
[error] Expected 'debug'
[error] Expected 'info'
[error] Expected 'warn'
[error] Expected 'error'
[error] Expected 'addPluginSbtFile'
[error] -J-Dhttp
[error]  ^

The SBT documentation lists many properties (all of which contain dots) but fails to provide any full command line examples of how to actually specify them. It seems like you should be able to "just" do -Dprop=value as in my first example: https://www.scala-sbt.org/1.x/docs/Command-Line-Reference.html

(Yes, there are more recent versions of SBT available, but I'm blocked on this bug: https://github.com/sbt/sbt/issues/5046 - ideally any solution works with any recent-ish version of SBT)

Answer 1

First, some background...

There are different ways to install SBT. Usually it comes with a wrapper shell script which makes it convenient to run so you don't have to specify sbt jar file location. However, depending on your installation method you might have a very simple or much more advanced sbt wrapper script.

I suggest to actually check your sbt runner script once to see what it does. Some basic scripts or manually created ones do NOT pass cmd args to JVM at all!

Here is one popular sbt runner script you can use: https://github.com/paulp/sbt-extras.

To get it simply make a script like this get_sbt.sh:

#!/bin/bash
curl -s https://raw.githubusercontent.com/paulp/sbt-extras/master/sbt > sbt \
  && chmod 0755 sbt

and it will download it for you.

On Fedora Linux (and other non-windows OSes) you can simply install sbt with package manager:

dnf install sbt

Here is a help page from my fedora sbt package:

$ sbt --help

...
  # jvm options and output control
  JAVA_OPTS           environment variable, if unset uses "-Dfile.encoding=UTF-8"
  .jvmopts            if this file exists in the current directory, its contents
                      are appended to JAVA_OPTS
  SBT_OPTS            environment variable, if unset uses ""
  .sbtopts            if this file exists in the current directory, its contents
                      are prepended to the runner args
  /etc/sbt/sbtopts    if this file exists, it is prepended to the runner args
  -Dkey=val           pass -Dkey=val directly to the java runtime
  -J-X                pass option -X directly to the java runtime
                      (-J is stripped)
  -S-X                add -X to sbt's scalacOptions (-S is stripped)

And a similar help from the github script above:

$ ./sbt -h

...

  # passing options to the jvm - note it does NOT use JAVA_OPTS due to pollution
  # The default set is used if JVM_OPTS is unset and no -jvm-opts file is found
  <default>         -Xms512m -Xss2m -XX:MaxInlineLevel=18
  JVM_OPTS          environment variable holding either the jvm args directly, or
                    the reference to a file containing jvm args if given path is prepended by '@' (e.g. '@/etc/jvmopts')
                    Note: "@"-file is overridden by local '.jvmopts' or '-jvm-opts' argument.
  -jvm-opts <path>  file containing jvm args (if not given, .jvmopts in project root is used if present)
  -Dkey=val         pass -Dkey=val directly to the jvm
  -J-X              pass option -X directly to the jvm (-J is stripped)

  # passing options to sbt, OR to this runner
  SBT_OPTS          environment variable holding either the sbt args directly, or
                    the reference to a file containing sbt args if given path is prepended by '@' (e.g. '@/etc/sbtopts')
                    Note: "@"-file is overridden by local '.sbtopts' or '-sbt-opts' argument.
  -sbt-opts <path>  file containing sbt args (if not given, .sbtopts in project root is used if present)
  -S-X              add -X to sbt's scalacOptions (-S is stripped)

... Now the answer:

You can test whether the properties are passed correctly to sbt like so:

$ echo 'sys.props.get("test")' | sbt -Dtest=works console
...
scala> sys.props.get("test")
res0: Option[String] = Some(works)

If you see None then your runner script is not doing its job, reinstall SBT or replace the script.

If that works but your port doesn't change, then perhaps the path in your config is different. Each dot in typesafe config represents a level of hierarchy (in json). You can print full config on start to see how it's structured.