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SBT Plugin to create a "start" script to run the program
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README.md

Consider sbt-native-packager instead

The more general native-packager plugin may replace this one in the future: https://github.com/sbt/sbt-native-packager

The rough way to get a start script with sbt-native-packager, modulo any details of your app, is:

  1. add sbt-native-packager plugin to your project
  2. remove start-script-plugin
  3. add settings(com.typesafe.sbt.SbtNativePackager.packageArchetype.java_application: _*)
  4. stage task will now generate a script target/universal/stage/bin/project-name instead of target/start
  5. the sbt-native-packager-generated script looks at a java_opts env var but you cannot pass Java opts as parameters to the script as you could with target/start
  6. the sbt-native-packager-generated script copies dependency jars into target/, so you don't need the Ivy cache

Many were using sbt-start-script with Heroku, sbt-native-packager has two tricky things on Heroku right now:

  1. Heroku sets JAVA_OPTS and not java_opts. See https://github.com/sbt/sbt-native-packager/issues/47 and https://github.com/sbt/sbt-native-packager/issues/48 ... for now you have to manually configure java_opts and not specify memory options, or hack sbt-native-packager.
  2. You need to hack the build pack to drop the Ivy cache, or your slug will be bloated or even exceed the max size.

Also of course you have to change your Procfile for the new name of the script.

About this plugin (sbt-start-script)

This plugin allows you to generate a script target/start for a project. The script will run the project "in-place" (without having to build a package first).

The target/start script is similar to sbt run but it doesn't rely on SBT. sbt run is not recommended for production use because it keeps SBT itself in-memory. target/start is intended to run an app in production.

The plugin adds a task start-script which generates target/start. It also adds a stage task, aliased to the start-script task.

stage by convention performs any tasks needed to prepare an app to be run in-place. Other plugins that use a different approach to prepare an app to run could define stage as well, while start-script is specific to this plugin.

The target/start script must be run from the root build directory (note: NOT the root project directory). This allows inter-project dependencies within your build to work properly.

Details

To use the plugin with SBT 0.12.x:

addSbtPlugin("com.typesafe.sbt" % "sbt-start-script" % "0.9.0")

You can place that code in ~/.sbt/plugins/build.sbt to install the plugin globally, or in YOURPROJECT/project/plugins.sbt to install the plugin for your project.

To use with SBT 0.13.x:

addSbtPlugin("com.typesafe.sbt" % "sbt-start-script" % "0.10.0")

Note: the global directory for 0.13.x is ~/.sbt/0.13 instead of ~/.sbt.

If you install the plugin globally, it will add a command add-start-script-tasks to every project using SBT. You can run this command to add the tasks from the plugin, such as start-script (the start-script task won't exist until you add-start-script-tasks).

If you incorporate the plugin into your project, then you'll want to explicitly add the settings from the plugin, such as the start-script task, to your project. In this case there's no need to use add-start-script-tasks since you'll already add them in your build.

Here's how you add the settings from the plugin in a build.sbt:

import com.typesafe.sbt.SbtStartScript

seq(SbtStartScript.startScriptForClassesSettings: _*)

In an SBT "full configuration" you would do something like:

settings = SbtStartScript.startScriptForClassesSettings

You have to choose which settings to add from these options:

  • startScriptForClassesSettings (the script will run from .class files)
  • startScriptForJarSettings (the script will run from .jar file from 'package')
  • startScriptForWarSettings (the script will run a .war with Jetty)

startScriptForWarSettings requires https://github.com/siasia/xsbt-web-plugin/ to provide the package-war task.

If you have an aggregate project, you may want a stage task even though there's nothing to run, just so it will recurse into sub-projects. One way to get a stage task that does nothing is:

SbtStartScript.stage in Compile := Unit

which sets the stage key to Unit.

Key names

Note that all the keys (except stage) are in the SbtStartScript.StartScriptKeys object, so the scala version of the start-script key is SbtStartScript.StartScriptKeys.startScript. This is the standard convention for sbt plugins. Do an import SbtStartScript.StartScriptKeys._ if you want all the keys unprefixed in your scope. Then, if you want to change a setting, you can simply reference the key directly in your `build.sbt'.

For example, to change the filename of the generated script to something other than target/start (which is controlled by the key SbtStartScript.StartScriptKeys.startScriptName), add the following to build.sbt after the above import statement:

startScriptName <<= target / "run"

Migration from earlier versions of xsbt-start-script-plugin

After 0.5.2, the plugin and its APIs were renamed to use consistent conventions (matching other plugins). The renamings were:

  • the plugin itself is now sbt-start-script not xsbt-start-script-plugin; update this in your plugins.sbt
  • the Maven group and Java package are now com.typesafe.sbt rather than com.typesafe.startscript; update this in your plugins.sbt and in your build files
  • the plugin object is now SbtStartScript rather than StartScriptPlugin, update this in your build files
  • if you used any keys directly, they are now inside a nested object StartScriptKeys so for example rather than writing startScriptFile you would write StartScriptKeys.startScriptFile or you need to import StartScriptKeys._
  • StartScriptKeys.startScriptFile did not match the string name of that settings start-script-name so now you should use StartScriptKeys.startScriptName

License

sbt-start-script is open source software licensed under the Apache 2.0 License.

Contribution policy

Contributions via GitHub pull requests are gladly accepted from their original author. Before sending the pull request, please agree to the Contributor License Agreement at http://typesafe.com/contribute/cla (it takes 30 seconds; you use your GitHub account to sign the agreement).

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