Using Spring & Java Annotations to Inject Reusable Capabilities – Part II

In an earlier post, I wrote about using the Spring BeanPostProcessor to inject cross-cutting concerns. That can easily be extended to inject a proxy more transparently across all beans in the application context. The key is to use the BeanFactoryPostProcessor in conjunction with the post-processor.  Define a custom class that implements the factory post processor like the following:

package learn;

public class ExampleBeanPostProcessorFactory implements BeanPostProcessorFactory {

	@Override
	void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {

		beanFactory.addBeanPostProcessor(new ExampleBeanPostProcessor());
	}

}

Define this bean alongside the the rest of your declarations. For instance:

<bean class="learn.ExampleBeanPostProcessorFactory" />

The post processor can be injected with required dependencies per your needs – this could be a bean that wraps all annotated objects with instrumentation via the Java Dynamic proxy. The key benefit is that the beans in your context can all be transparently examined and proxied – how to decide which beans need to be proxied can be determined by annotations or beans implementing certain interfaces or custom decision logic using a class.