Improve reference documentation for Task Execution and Scheduling about bean scopes [SPR-14167]

[spring-projects-issues]

Manuel Jordan opened SPR-14167 and commented

I am doing some experiments about Task Execution and Scheduling

In XML I have the following:

<bean id="processServiceImpl"
           scope="prototype"
           class="com.manuel.jordan.service.impl.ProcessServiceImpl" />

<task:scheduler id="scheduler" pool-size="4" />

<task:scheduled-tasks scheduler="scheduler" >
	
                <task:scheduled ref="processServiceImpl" 
					   method="executeRunnable" 
                                           initial-delay=3000"						 
                                           fixed-rate="10000"   
						/>						
                <task:scheduled ref="processServiceImpl" 
                                           method="executeCallable" 
                                           initial-delay="30000"						 
                                           fixed-rate="10000"   
						/>
						
</task:scheduled-tasks>

Until here my processServiceImpl bean is prototype

My code works well how is expected, I can see two instances working well, it about the executeRunnable and executeCallable methods... I can confirm this through the terminal and with visualVM.

Until here, I can assume I can work in peace with a prototype object with scheduling

But in JavaConfig I have a situation:

@Configuration
@EnableScheduling
public class SchedulingConfig implements SchedulingConfigurer {

	@Override
	public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
		taskRegistrar.setScheduler(taskScheduler());
	}
	
	@Bean(destroyMethod="shutdown")
    public TaskScheduler taskScheduler() {
		
		ThreadPoolTaskScheduler threadPoolTaskScheduler = new ThreadPoolTaskScheduler();
		threadPoolTaskScheduler.setPoolSize(4);
		
		return threadPoolTaskScheduler;
    }

}

And with:

@Service
//@Scope(value=ConfigurableBeanFactory.SCOPE_SINGLETON)
@Scope(value=ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public class ProcessServiceImpl implements ProcessService, Runnable, Callable<String> {

	private static final Logger logger = LoggerFactory.getLogger(ProcessServiceImpl.class.getSimpleName());
	
	@Override
	@Scheduled(initialDelay=3000, fixedRate=10000)
	public void executeRunnable() {
		new MessageRunnableWithSleep().run();
	}
...

When I execute the code

public static void main(String[] args) throws Exception {
				
		ConfigurableApplicationContext applicationContext = new AnnotationConfigApplicationContext(CentralConfig.class);
		
		MainScheduleSupport.sleep();
		
		applicationContext.close();
		
}

I did realise only works on Singleton, but not Prototype.

(1) I am confused, why prototype did work on XML and not in JavaConfig + Annotations. Did I forget something?
(2) On 33. Task Execution and Scheduling, there is no mention neither about Singleton nor Prototype

From (1) If scheduling is only valid on Singleton, I am assuming that on XML even when the bean is prototype the two <task:scheduled declarations work with one instance...

The point, the explanation should be added in the reference documentation and javadoc to avoid confusions.

---

Affects: 4.2 GA, 4.2.4

Issue Links:

• @Scheduled methods in @Lazy beans are not scheduled [SPR-12872] #17470 @Scheduled methods in @Lazy beans are not scheduled
• ScheduledAnnotationBeanPostProcessor should unregister tasks on destruction of individual beans [SPR-12216] #16830 ScheduledAnnotationBeanPostProcessor should unregister tasks on destruction of individual beans

Referenced from: commits d628420

[spring-projects-issues]

Manuel Jordan commented

Just to confirm

I have re-tested my two projects, based on:

• XML
• JavaConfig

All works fine with singleton

[spring-projects-issues]

Juergen Hoeller commented

As of 4.3 RC2, ScheduledAnnotationBeanPostProcessor features a revised registration mechanism capable of tracking individual bean instances, both on creation for beans of any scope and on destruction of each individual bean. In other words, @Scheduled works on any Spring-managed bean now, not just on non-lazy singleton beans anymore.

So I suppose that there aren't any restrictions left to document. If there is nevertheless something you'd like to see improved in the wording or the examples, let me know.

[spring-projects-issues]

Manuel Jordan commented

Hi Juergen

In other words, @Scheduled works on any Spring-managed bean now, not just on non-lazy singleton beans anymore.

If that means now that @Scheduled (from 4.3 RC2) can be applied to prototypes beans. Has sense to left the documentation without changes, but perhaps add a note for XML and annotations sections indicating it has been improved would be nice, it of course because it is a new feature.