Programmatically restart Spring Boot application / Refresh Spring Context

Even though Alex’s solution works, I don’t believe in including 2 additional dependencies (Actuator and Cloud Context) just to be able to do one operation. Instead, I have combined his answer and modified my code in order to do what I wanted.

So, first of all, it is crucial that the code is executed using new Thread() and setDaemon(false);. I have the following endpoint method that handles the restart:

val restartThread = Thread {
    logger.info("Restarting...")
    Thread.sleep(1000)
    SpringMain.restartToMode(AppMode.valueOf(change.newMode.toUpperCase()))
    logger.info("Restarting... Done.")
}
restartThread.isDaemon = false
restartThread.start()

The Thread.sleep(1000) is not required, but I want my controller to output the view before actually restarting the application.

SpringMain.restartToMode has the following:

@Synchronized fun restartToMode(mode: AppMode) {
    requireNotNull(context)
    requireNotNull(application)

    // internal logic to potentially produce a new arguments array

    // close previous context
    context.close()

    // and build new one using the new mode
    val builder = SpringApplicationBuilder(SpringMain::class.java)
    application = builder.application()
    context = builder.build().run(*argsArray)
}

Where context and application come from the main method upon starting the application:

val args = ArrayList<String>()
lateinit var context: ConfigurableApplicationContext
lateinit var application: SpringApplication

@Throws(Exception::class)
@JvmStatic fun main(args: Array<String>) {
    this.args += args

    val builder = SpringApplicationBuilder(SpringMain::class.java)
    application = builder.application()
    context = builder.build().run(*args)
}

I am not entirely sure if this produces any problems. If there will be, I will update this answer. Hopefully this will be of any help to others.