Spring trying to understanding BeanPostProcessor

[Kim Ming Yap]

I'm newbie to Spring and i'm trying to understand the BeanPostProcessor - postProcessBeforeInitialization and postProcessAfterInitialization.

In short:

1) spring.xml

     <?xml version="1.0" encoding="UTF-8"?>
     <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd">
     <beans>
      <bean id="triangle1" class="org.tutorial.spring.TrianglePostProcessor">
		<property name="pointA">
			<bean class="org.tutorial.spring.Point">
				<property name="x" value="-100" />
				<property name="y" value="-200" />
			</bean>
		</property>
      </bean>
      <bean class="org.tutorial.spring.DisplayBeanNamePostProcessor" />
     </beans>

2) TrianglePostProcessor.java

    package org.tutorial.spring;

    public class TrianglePostProcessor  {

	private Point pointA;

	public Point getPointA() {
		return pointA;
	}

	public void setPointA(Point pointA) {
		System.out.println("setPointA");
		this.pointA = pointA;
	}
	
    }

3) DisplayBeanNamePostProcessor.java

    package org.tutorial.spring;

    import org.springframework.beans.BeansException;
    import org.springframework.beans.factory.config.BeanPostProcessor;

    public class DisplayBeanNamePostProcessor implements BeanPostProcessor {

	@Override
	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
		System.out.println("In postProcessAfterInitialization bean = " + beanName);
		return bean;
	}

	@Override
	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
		System.out.println("In postProcessBeforeInitialization bean = " + beanName);
		return bean;
	}

    }

4) DrawingApp.java

    package org.tutorial.spring;

    import org.springframework.context.support.AbstractApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;

    public class DrawingApp {

	public static void main(String[] args) {
		AbstractApplicationContext context = new ClassPathXmlApplicationContext("springPostProcessor.xml");
		context.registerShutdownHook();
		TrianglePostProcessor triangle = (TrianglePostProcessor)   context.getBean("triangle1");
    //		triangle.draw();
		context.close();
	}

    }

Now when i run the DrawingApp, i got the following messages:


In postProcessBeforeInitialization bean = org.tutorial.spring.Point#5f0101fb
In postProcessAfterInitialization bean = org.tutorial.spring.Point#5f0101fb
setPointA
In postProcessBeforeInitialization bean = triangle1
In postProcessAfterInitialization bean = triangle1

The `postProcessBeforeInitialization` as its word says should be before initialization but as you can see from the log, the setPointA is executed first and then the `postProcessBeforeInitialization` ..

Did I miss something?

[Jayesh A Lalwani]

The properties of the bean are set right after the bean is created. The BeanPostProcessor.processBeforeInitialization is called before calling the init method of the bean

[Kim Ming Yap]

So the BeanPostProcessor and InitializingBean is pretty much the same except that the former can be done for a large group of beans instead of per bean.
Also i noticed that BeanPostProcessor is done before the initializingBean if both of this exists.
But in theory they are the same.
am i right?