NPE if BeanPostProcessor returns null [SPR-6926]

[spring-projects-issues]

Daniel Walcher opened SPR-6926 and commented

We have a BeanPostProcessor that converts configuration beans into their actual value, sometimes the value is a 'null'. This causes a NPE as other internal spring BeanPostProcessor's do not correctly handle a null value.

Is this a bug or are we doing something wrong?

For example the org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor#postProcessBeforeInitialization does not validate the bean, attempting to call 'bean.getClass()' which causes a NPE.

Should it not prevent running other post processors if the bean has been nulled? i.e.:

	public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
			throws BeansException {

		Object result = existingBean;
		for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
			if (result == null) return;
			result = beanProcessor.postProcessBeforeInitialization(result, beanName);
		}
		return result;
	}

Also can someone confirm that the org.springframework.core.Ordered interface works for BeanPostProcessor. We have been unable to use this to create a work around, investigation has indicated that the logic seems to be missing to enforce ordering.

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Affects: 3.0 GA, 3.0.1

Referenced from: commits 6118d67, 8975554

[spring-projects-issues]

Daniel Walcher commented

Further investigation has shown that AbstractAutowireCapableBeanFactory#applyBeanPostProcessorsAfterInitialization also suffers from the same issue.

[spring-projects-issues]

Juergen Hoeller commented

Fixed for 3.0.2: BeanPostProcessors are allowed to return a null bean value in the middle of the chain now.

As for your ordering question: BeanPostProcessors will only honor the Ordered interface when autodetected as beans (see AbstractApplicationContext's "registerBeanPostProcessors"). Objects registered through addBeanPostProcessor do not participate in that ordering; the addBeanPostProcessor call order is significant there.

Juergen