Spring: How to ensure order of bean registration to container?

Question

I have a set of service classes that are spread across different maven modules in my application.

public class ServiceA implements IsService
{
   public void startA()
   {
       ....
   }
}

public class ServiceB implements IsService
{
   public void startB()
   {
       ....
   }
}

Creating a configuration class to detect and register only the classes that implement the IsService interface.

@Configuration
@ComponentScan(basePackages = {"com.subex.roc"} , 
              useDefaultFilters = false , 
              includeFilters = {@Filter(type = FilterType.ASSIGNABLE_TYPE,value = IsService.class)})
public class ServiceRegisterConfig 
{
}

Fetching the registered classes and calling start() polymorphically.

  public void initServerServices()
    {
        AnnotationConfigApplicationContext context = new  AnnotationConfigApplicationContext();
        context.register(ServiceRegisterConfig.class);
        context.refresh();

        for (String beanDfn : context.getBeanDefinitionNames()) 
        {
          if (context.getBean(beanDfn) instanceof IsService) {
          IsService service = (IsService) context.getBean(beanDfn);
          service.start();
        }
     } 
    }

However I want to ensure that ServiceA 's start() is called first and then ServiceB as ServiceB depends on the initialization of ServiceA. Can the container somehow ensure this?

Tried DependsOn. But start() of services being called in the order of their encounter in classpath.DependsOn not being honoured.

Possible duplicate of [Spring: Make sure a particular bean gets initialized first](http://stackoverflow.com/questions/7868335/spring-make-sure-a-particular-bean-gets-initialized-first) — Software Engineer, Mar 28 '16 at 03:37

score 1 · Answer 1 · answered Mar 28 '16 at 03:40

1

Use the depends-on attribute, but if you get into trouble you can always hack in a post processor factory...

public class PreInitializer implements BeanFactoryPostProcessor, PriorityOrdered {  
 @Override  
 public int getOrder() {  
  return Ordered.HIGHEST_PRECEDENCE;  
 }  
 @Override  
 public void postProcessBeanFactory(  
   ConfigurableListableBeanFactory beanFactory) throws BeansException {  
  /* put initialization code here */  
 }  
}

answered Mar 28 '16 at 03:40

Software Engineer

15,457
7
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Implementing PriorityOrdered would mean I have to go and update the services classes.I'm looking for a solution where I can define this order externally.depends-on seems viable.Is there is java-based or annotation based alternative for depends-on? – Priyanka.Patil Mar 28 '16 at 03:52
@Priyanka.Patil you can use `DependsOn` annotation on declarations of your beans. But in this case you have to declare every bean manually in configuration class. – Ken Bekov Mar 28 '16 at 04:04
Tried `DependsOn`. But start() of services being called in the order of their encounter in classpath.`DependsOn` not being honoured. – Priyanka.Patil Mar 28 '16 at 07:00

Sanj · Answer 2 · 2016-03-28T05:14:53.117

0

BeanFactoryPostProcessor can be used to set dependencies

public class DependencyConfigurer implements BeanFactoryPostProcessor, PriorityOrdered {

    @Override  
 public int getOrder() {  
  return Ordered.HIGHEST_PRECEDENCE;  
 } 

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

            BeanDefinition bd = beanFactory.getBeanDefinition("serviceB");
            bd.setDependsOn("serviceA");


    }



}

Alternatively you can use DependsOn annotation

@Bean(name="ServiceA") 
   public class ServiceA implements IsService
    {
       public void startA()
       {
           ....
       }
    }

@Bean(name="ServiceB")
@DependsOn("ServiceA")
public class ServiceB implements IsService
{
   public void startB()
   {
       ....
   }
}

Finally XML configuration can be used

<bean class="com.foo.ServiceA" name="serviceA"/>

<bean class="com.foo.ServiceB" depends-on="serviceA"/>

edited Mar 28 '16 at 05:14

answered Mar 28 '16 at 03:52

Sanj

3,879
2
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Can `@DependsOn` be used in a `@configuration` annotated class (which will have a list of service class declarations) instead of `@bean` annotated class. – Priyanka.Patil Mar 28 '16 at 03:56
any reason you want it that way? – Sanj Mar 28 '16 at 03:57
Want to keep the service classes clean of dependency management. – Priyanka.Patil Mar 28 '16 at 03:58
xml configuration is an option too. – Sanj Mar 28 '16 at 04:39
updated my post. BeanFactoryPostProcessor can work for you. – Sanj Mar 28 '16 at 05:29
Tried `DependsOn`. But start() of services being called in the order of their encounter in classpath.`DependsOn` not being honoured. – Priyanka.Patil Mar 28 '16 at 07:02
start methods are configured as init-method/@PostConstruct? How are start methods invoked? – Sanj Mar 28 '16 at 16:58
In the question I have mentioned initServerServices() methods which gets the registered bean definition names and iterated over that list to start the services. – Priyanka.Patil Mar 29 '16 at 02:01
There is no need for initServerServices() if you make the start methods as @PostConstruct/init-method? – Sanj Mar 29 '16 at 02:12

Spring: How to ensure order of bean registration to container?

2 Answers2