Cleanly destroy Spring Application Context

Question

I have been running in to problems making sure that a spring application context that i am destroying has completely gone away, and cant see the object being garbage collected. When i look at the instance in VisualVM i can see that there are a number of outstanding references to both the context and it's bean factory that remain once the context is closed and destroyed. These all to be in relation to the initial set up of the bean factory (during the refresh method of AbstractApplicationContext) which registers the bean factory and the context with various bean post processors etc.

There do not appear to be any methods on the bean factory or on the application contexts (even the refreshable ones) that do more than remove the lowest level reference to the bean factory. The result is that it appears to be leaking memory, and in certain circumstances preventing the clean re-creation of a context.

I am asking as the software i am working on at the moment may dynamically create / destroy and then re-create the context (as modules are dynamically loaded and unloaded) and the leftover elements of the context and bean factory are causing problems with components such as spring-data-jpa (especially the proxy that binds the repository interfaces to the repository implementations).

Does anyone know of a way whereby i can cleanly and completely remove a context and bean factory without having to completely close down the VM that initially created it?

score 1 · Answer 1 · edited Jan 04 '17 at 11:23

Having looked into this again recently, i noticed that i was overriding the doClose() method of the context to make sure beans were completely destroyed, but was not calling the super.doClose() method, which meant that LiveBeansView.unregisterApplicationContext() / destroyBeans() / getLifecycleProcessor().onClose() and closeBeanFactory() were not being called.

I added this in, and (most) if not all contexts are now cleanly destroyed and garbage collected. I will assume that any outstanding contexts that are not destroyed are more probably issues in our own code with dangling references.

score 0 · Answer 2 · edited Dec 23 '16 at 13:07

If you are using Spring's IoC container in a non-web application environment; for example, in a rich client desktop environment; you register a shutdown hook with the JVM. Doing so ensures a graceful shutdown and calls the relevant destroy methods on your singleton beans so that all resources are released. Of course, you must still configure and implement these destroy callbacks correctly.

To register a shutdown hook, you should call the registerShutdownHook() method that is declared on the AbstractApplicationContext class:

Code

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public final class startup {

  public static void main(final String[] args) throws Exception {
      AbstractApplicationContext ctx
          = new ClassPathXmlApplicationContext(new String []{"beans.xml"});

      // add a shutdown hook for the above context... 
      ctx.registerShutdownHook();

      // app runs here...

      // main method exits, hook is called prior to the app shutting down...
  }
}

Thanks, but as i mentioned this has nothing to do with the shutdown of the overall container. This is a creation/destruction of an application context without shutting down the container, so a shutdown hook wont help. — Mike, Dec 28 '16 at 20:53

score 0 · Answer 3 · answered Dec 27 '16 at 16:56

0

Call destroy on context and set null to all variables referencing instance of your application context:

AbstractApplicationContext context = new ClassPathXmlApplicationContext(new String []{"beans.xml"});

// ... do your stuff

context.destroy();
context = null;

answered Dec 27 '16 at 16:56

walkeros

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Thanks, but i have looked into destroy and it is there only as a very special case (where a context is a bean inside another bean factory) and in any event the default implementation just calls close(); I am most definately closing the context and removing any references to the context, but the point is that the bean factory inside the application context registers itself (or is registered by) a number of other internal instances in Spring and therefore the overall reference is never released (setting it to null everywhere in our code has no effect. – Mike Dec 28 '16 at 20:55

Cleanly destroy Spring Application Context

3 Answers3