Programmatically restart Spring Boot application / Refresh Spring Context

Question

I am trying to programmatically restart my Spring Application without having the user to intervene.

Basically, I have a page which allows to switch the mode of the application (actually meaning switching the currently active profile) and as far as I understand I must restart the context.

Currently my code is very simple, it's just for the restarting bit (this is Kotlin by the way):

    context.close()
    application.setEnvironment(context.environment)
    ClassUtils.overrideThreadContextClassLoader(application.javaClass.classLoader)
    context = application.run(*argsArray)

However the moment I do context.close() the JVM exists immediately. I have also tried context.refresh() but that seems to simply kill Tomcat/Jetty (tried both just in case it was a Tomcat problem) and then nothing happens.

I have also seen Programmatically restart Spring Boot application but nothing seems to work for me from those answers. Furthermore, I looked into Spring Actuator which supposedly has the /restart endpoint, but that doesn't seem to be there anymore?

Answer 1

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.

Answer 2

As was commented already, the restart-via-thread implementations given before only work once, and second time around throw a NPE because context is null.

This NPE can be avoided by having the restart thread use the same class loader as the initial main-invoking thread:

private static volatile ConfigurableApplicationContext context;
private static ClassLoader mainThreadClassLoader;

public static void main(String[] args) {
    mainThreadClassLoader = Thread.currentThread().getContextClassLoader();
    context = SpringApplication.run(Application.class, args);
}

public static void restart() {
    ApplicationArguments args = context.getBean(ApplicationArguments.class);

    Thread thread = new Thread(() -> {
        context.close();
        context = SpringApplication.run(Application.class, args.getSourceArgs());
    });

    thread.setContextClassLoader(mainThreadClassLoader);
    thread.setDaemon(false);
    thread.start();
}