I have a spring boot 3 snapshots app with nothing on the classpath save spring-boot-starter with spring boot 3 aot and graalvm apps.

if I use the code:

package shutdown.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class DemoApplication {

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

    @Bean
    Controller myController  (){
        return new ControllerManager();
    }
}

class ControllerManager implements Controller {

    @Override
    public void shutdown() {
        System.out.println("calling ControllerManager#shutdown" );
    }
}

interface Controller {

    void shutdown() ;
}

and then compile/run in a graalvm application, I get the following error:

022-11-21T17:56:24.631-08:00 INFO 66325 --- [ main] shutdown.demo.DemoApplication : No active profile set, falling back to 1 default profile: "default" 2022-11-21T17:56:24.633-08:00 WARN 66325 --- [ main] o.s.c.support.GenericApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'myController': Invalid destruction signature 2022-11-21T17:56:24.633-08:00 ERROR 66325 --- [ main] o.s.boot.SpringApplication : Application run failed

If I return ControllerManager from the @Bean method, that works.

It's still pretty dissatisfying when I have a builder that returns Controller, and not the subclass, and I have no way of knowing what subclass it is. Plus, it works on the JVM with no issues even with just the interface.

I know there is a best practice that we should use direct subclasses in @Bean method return types, but this feels like a different kind of bug, especially since shutdown is visible on the interface and the subclass.

The other issue here is that it is not my intent that this shutdown be used to clean up the bean when the application context shuts down. That is, I don’t want this to be used as the spring bean destroyMethod; it’s just a method that happened to be on the class. So to get these inscrutable errors about Invalid destruction signature is weird.

Comment From: snicoll

Thanks for the sample. I am afraid there's nothing we can do as the actual type is not exposed for AOT inference. This sample works on the JVM with AOT. It also works in Native if you add the following to the application:

hints.reflection().registerMethod(
        ReflectionUtils.findMethod(ControllerManager.class, "shutdown"),
        ExecutableMode.INVOKE);

It also works, as you found out yourself, if you expose the actual type (which is what you should be doing regardless of AOT).

It's still pretty dissatisfying when I have a builder that returns Controller, and not the subclass, and I have no way of knowing what subclass it is. Plus, it works on the JVM with no issues even with just the interface.

I can see how that can be problematic but it is the very nature of building a native image where things have to be known at build time. The shutdown method on ControllerManager simply doesn't exist because there's no way for us to know that type needs to be harvested.

The only thing I can see us doing is failing early if we detect a shutdown method on a type that isn't concrete. Flagging for team attention to see what the rest of the team thinks.

Comment From: snicoll

I forgot to mention that a proper fix for this would be to generate code for the method invocation, something like:

bd.onShutdown((instance) -> instance.shutdown());

@poutsma is considering exposing an API (#29553) that could help with this, I think.

Comment From: sbrannen

The other issue here is that it is not my intent that this shutdown be used to clean up the bean when the application context shuts down. That is, I don’t want this to be used as the spring bean destroyMethod; it’s just a method that happened to be on the class. So to get these inscrutable errors about Invalid destruction signature is weird.

@joshlong, are you aware that the shutdown() method is being invoked due to default destroy method inference which looks for close() and shutdown() methods?

You can disable that inference by annotating your bean factory method with @Bean(destroyMethod = "").

If you run the following test class, you will not see ControllerManager#shutdown() invoked! printed to the console; however, if you switch back to @Bean you'll see the message printed to the console again.

@SpringJUnitConfig
class ShutdownTests {

    @Test
    void test() {
    }

    @Configuration
    static class Config {

        @Bean(destroyMethod = "")
        Controller myController() {
            return new ControllerManager();
        }
    }

    interface Controller {
        void shutdown();
    }

    static class ControllerManager implements Controller {

        @Override
        public void shutdown() {
            System.err.println("ControllerManager#shutdown() invoked!");
        }
    }

}

Comment From: moray95

Hello, I am facing a similar issue while trying to migrate an application to GraalVM native image and would like to give an alternate view as this issue appears to me to be much more troublesome then mentioned here.

I am trying to migrate an application using Spring Boot 3.0.4 and Hazelcast 5.2.1. When I boot up the application, I get a similar error for HazelcastInstance.shutdown method. When I look at the generated reflect-config.json, I can properly see a related entry:

{
  "name": "com.hazelcast.core.HazelcastInstance",
  "methods": [
    {
      "name": "shutdown",
      "parameterTypes": [ ]
    }
  ]
}

Possible workarounds: - Removing the destroyMethod: I am unable to easily do this as this bean is created by Spring Boot auto-configurations (and it probably wouldn't be a good idea anyway). - Exposing a bean with the concrete type: this is not practical as it's not really possible to determine the concrete type of the bean, again coming from Sprint Boot auto-configurations. Even the Spring Boot auto-configuration is unable to tell the concrete type as it's an implementation detail within the Hazelcast dependency. - Adding reflection configuration for the concrete types: Even though it's probably the best approach for now, it's very cumbersome since there are 7 different known concrete implementation of this interface. Moreover, new implementations might break the application. This method also takes away the abstraction provided by using an interface as it leaks implementation details.

Adding the fact there are probably many other auto-configurations that might cause similar issues, I think it's best if this can be solved within Spring.

Cause and possible solution:

After some trials with GraalVM native images, I have found that defining an interface in reflect-config does work when accessing the method trough the interface but not from the concrete type.

Example:

reflect-config.json:

[
  {
    "name": "org.example.Printer",
    "methods": [
      {
        "name": "print",
        "parameterTypes": [ ]
      }
    ]
  }
]

interface Printer {
    fun print()
}

class HelloWorldPrinter: Printer {
    override fun print() {
        println("Hello world")
    }
}

val printer: Printer = HelloWorldPrinter()

// This works
Printer::class.java.getMethod("print").invoke(printer)

// This doesn't work
HelloWorldPrinter::class.java.getMethod("print").invoke(printer)

It looks like Spring is using the second approach while searching for destroy methods. Transitioning to the first approach would most likely fix this issue. The bean definition type looks like is present in RootBeanDefinition as targetType, resolvedTargetType or factoryMethodReturnType (I might be wrong wrong on this as I am not familiar with Spring internals).