[Spring] 스프링 BeanPostProcessor

BeanPostProcessor

Bean 객체를 정의할 때  init-method 속성을 설정하면 객체가 생성될 때 자동으로 호출될 메서드를 지정할 수 있다.

 

이때 BeanPostProcessor 인터페이스를 구현한 클래스를 정의하면 Bean 객체를 생성할 때 호출될 init 메서드 호출을 가로채 다른 메서드를 호출할 수 있도록 할 수 있다.

 

Spring에서는 객체가 생성될 때 init-method로 지정된 메서드가 호출되기 전, 후에 다른 메서드를 호출할수 있도록 지원하고 있다. 

 

관련예제 ↓

 

메인클래스

package sanghoon.main;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import sanghoon.beans.TestBean1;
import sanghoon.beans.TestBean2;

public class MainClass {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		ClassPathXmlApplicationContext ctx= new ClassPathXmlApplicationContext("sanghoon/config/beans.xml");
		
		TestBean1 t1 = ctx.getBean("t1",TestBean1.class);
		System.out.printf("t1: %s\n",t1);
		
		System.out.println("-----------------------------------");
		

		TestBean2 t2 = ctx.getBean("t2",TestBean2.class);
		System.out.printf("t2: %s\n",t2);
		
		ctx.close();
	}

}

package sanghoon.beans;

public class TestBean1 {
	
	public TestBean1() {
		System.out.println("TestBean1의 생성자");
	}

	public void bean1_init() {
		System.out.println("TestBean1의 init 메서드");
	}
}

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://www.springframework.org/schema/beans 
http://www.springframework.org/schema/beans/spring-beans.xsd"> 

	<bean id='t1' class= 'sanghoon.beans.TestBean1' lazy-init='true' init-method="bean1_init"/>
	<bean id='t2' class= 'sanghoon.beans.TestBean2' lazy-init='true' init-method="bean2_init"/>
	<bean class='sanghoon.processor.TestBeanPostProcessor'/>
</beans>

package sanghoon.beans;

public class TestBean2 {
	
	public TestBean2() {
		System.out.println("TestBean2의 생성자");
	}

	public void bean2_init() {
		System.out.println("TestBean2의 init 메서드");
	}
}

TestBeanPostProcessor

package sanghoon.processor;

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

public class TestBeanPostProcessor implements BeanPostProcessor{
	
	//init-method 호출 전 
	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
		// TODO Auto-generated method stub
		System.out.println("before");
		switch(beanName) {
		case"t1" :
			System.out.println("id가 t1인 bean객체 생성");
			break;
		case"t2" :
			System.out.println("id가 t2인 bean객체 생성");
			break;
		}
		return bean;
	}
	
	//init-method 후 
	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
		// TODO Auto-generated method stub
		System.out.println("after");
		return bean;
	}
}