Programmatically restart Spring Boot application / Refresh Spring Context

In case it might help someone, here's a pura Java translation of Crembo's accepted answer.

Controller method:

@GetMapping("/restart")
void restart() {
    Thread restartThread = new Thread(() -> {
        try {
            Thread.sleep(1000);
            Main.restart();
        } catch (InterruptedException ignored) {
        }
    });
    restartThread.setDaemon(false);
    restartThread.start();
}

Main class (significant bits only):

private static String[] args;
private static ConfigurableApplicationContext context;

public static void main(String[] args) {
    Main.args = args;
    Main.context = SpringApplication.run(Main.class, args);
}

public static void restart() {
    // close previous context
    context.close();

    // and build new one
    Main.context = SpringApplication.run(Main.class, args);

}

I've solved this issue by using Restarter from Spring Devtools. Add this to pom.xml:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
    <scope>runtime</scope>
</dependency>

Then use org.springframework.boot.devtools.restart.Restarter to call this:

Restarter.getInstance().restart();

It works for me. Hope this help.

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.