Introduce supports() method in BeanPostProcessor

[huifer]

When writing an implementation class for the BeanPostProcessor interface, you usually have the following code:

@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    if (bean instanceof People) {
        // do something
    }
    return bean;
}

The BeanPostProcessor interface implementation class needs to enter this code each time it passes through each if block, and some of these entries don't do anything to the bean object, but return it directly.

Maybe the BeanPostProcessor interface can have a supports() method to judge whether to support processing in the postProcessBeforeInitialization method.

The improved code is as follows.

public interface BeanPostProcessor  {
    @Nullable
    default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

    @Nullable
    default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

    default boolean supports(Object bean, String beanName) {
        return true;
    }
}

[sbrannen]

Related Issues

• Provide a mechanism to be notified that a bean has been created [SPR-16822] #21362 (comment)

[huifer]

Some of my thoughts

#21362 (comment)

[snicoll]

Thanks for the suggestion but BeanPostProcessor is a low-level interface and we'd rather not make it more complex at this time. Some improvements are scheduled in a separate issue, see #21362 (comment).