[Springframework-developer] Reversed dependencies

[Hagen O. <hag...@hp...>]

Hi all,


after looking at pico and hivemind, I finally took the time to dive in 
to spring. I got scared of at first, because I just wanted a container 
and there is soooo much else in the framework... but after finding 
spring-core.jar I got up to speed.

Anyway this it what I want to do:

large pool of containers
	| 1
	| *
specific pool, that has a component the the parent components depend on.


I am evaluating this design, because I don't want to replicate the 
parent pool each time, but its components are dependent on a use case 
specific component.

This is what I came up with:

package testing;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import 
org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
import org.springframework.core.io.Resource;


public class ReversedDependencyBeanFactory extends 
DefaultListableBeanFactory {
     private Map dependentSingeltonCache = new HashMap();

     public ReversedDependencyBeanFactory(BeanFactory aParent) {
         super(aParent);
     }

	public ReversedDependencyBeanFactory(Resource aResource, BeanFactory 
aParent) throws BeansException {
	    this(aParent);
	    (new XmlBeanDefinitionReader(this)).loadBeanDefinitions(aResource);
     }

	public ReversedDependencyBeanFactory(Resource aResource) throws 
BeansException {
	    this(aResource, null);
     }

     public Object getBean(String aName) throws BeansException {
         String theBeanName = transformedBeanName(aName);

         if (dependentSingeltonCache.containsKey(theBeanName)) {
             return dependentSingeltonCache.get(theBeanName);
         }
         try {
            return super.getBean(aName);
         } catch (BeansException ex) {
			RootBeanDefinition theDefinition = 
getMergedBeanDefinition(theBeanName, true);
			Object theBean = createBean(theBeanName, theDefinition);
			if (theDefinition.isSingleton()) {
			    dependentSingeltonCache.put(theBeanName, theBean);
			}
			return theBean;
         }
	}

     public void destroySingletons() {
		Set singletonCacheKeys = new 
HashSet(dependentSingeltonCache.keySet());
		for (Iterator theIterator = singletonCacheKeys.iterator(); 
theIterator.hasNext();) {
		    String theBeanName = (String) theIterator.next();
			Object theInstance = dependentSingeltonCache.remove(theBeanName);
			if (theInstance != null) {
				destroyBean(theBeanName, theInstance);
			}
		}
         super.destroySingletons();
     }
}

I also looked at a BeanFactoryAware FactoryBean, but it get's passed in 
the parent container only...

Anyway, this does pass my test cases (create a parent container, that 
has a dependency in the child and play around with it). Since I am very 
new to spring (2h in the source), I'd like feedback from the group.

Also, I am looking for a way to ask the child, which components of the 
parent (with a certain interface) it can instanciate (because it 
satifies its dependencies). I get a little confused about the 
Root/ChildBeanDefinition... and this has to perform also ;-)

Any suggestions greatly appreciated

Cheers
	)-(agen