Customize Spring Boot launch script

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I have a typical Spring Boot 2.x application. I'm currently deploying the application using Docker. I'm also using the built-in shell script that a "distribution" provides — when done via Gradle, read: assembleBootDist, installBootDist, etc.

The issue is that I have to execute (a) some other shell script before starting the application, (b) insert this shell script somehow the built-in one, (c) or something else that achieves the same.

So I wonder if there is a way to accomplish this in a clean way, without introducing any security concerns, etc. I've been trying to plug into the bootStartScripts (Gradle) task, but no luck there. I'm aware there is a launchScript property within bootJar, but as far as I can tell it replaces altogether the actual built-in script provided by Spring Boot — and I'm avoiding that.

Any other shell-fu would also work, provided nothing around security is compromised.

spring-boot gradle
2 Answers

This is kind of hack but with spring boot default script customization provided - may be you can use "inlinedConfScript" ( explained here) which basically points to a script meant to provide configuration but since it is a script file technically you can write scripting code as usual.

inlinedConfScript

Reference to a file script that should be inlined in the default launch script. This can be used to set environmental variables such as JAVA_OPTS before any external config files are loaded.

user_14430840

Another solution could be to (still) use the shell script that provides the custom logic and then execute (in the end) the built-in shell script generated by the Spring Boot "distribution" (Gradle) task:

#!/usr/bin/env sh

printf "%s\n" "Running some initialization steps..."
# ...

# This is the shell script generated by the Spring Boot "distribution" (Gradle) task
exec /path/to/application "$@"

Save this as, for instance: docker-entrypoint, and use it as usual in the Dockerfile's ENTRYPOINT instruction.

user_46952710
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