Spring BeanPostProcessor Example
October 29, 2021
BeanPostProcessor interface. The BeanPostProcessor interface works as factory hook that allows for custom modification of new bean instances. The BeanPostProcessor interface has following methods.
1.
Object postProcessBeforeInitialization(Object bean, String beanName)
afterPropertiesSet method of InitializingBean or a custom init-method. The properties of bean will already be populated before calling postProcessBeforeInitialization method. The returned bean by this method can be a wrapper around the original.
2.
Object postProcessAfterInitialization(Object bean, String beanName)
afterPropertiesSet method of InitializingBean or a custom init-method.
The
BeanPostProcessor can be used for following purposes.
1. Checking for marker interfaces using
postProcessBeforeInitialization() method.
2. Wrapping beans with proxies using
postProcessAfterInitialization method.
BeanPostProcessor with XML Configuration
Find the code to useBeanPostProcessor with XML configuration.
MyBeanPostProcessor.java
package com.concretepage;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
public class MyBeanPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException {
System.out.println("Inside post process after initialization: "+beanName);
return bean;
}
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName)
throws BeansException {
System.out.println("Inside post process before initialization: "+beanName);
return bean;
}
}
<?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="animal" class="com.concretepage.Animal" init-method="init" destroy-method="destroy">
<property name="name" value="Lion"/>
</bean>
<bean class="com.concretepage.MyBeanPostProcessor"/>
</beans>
package com.concretepage;
public class Animal {
private String name;
public void init() {
System.out.println("Inside init method");
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public void destroy() {
System.out.println("Inside destroy method");
}
}
package com.concretepage;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpringDemo {
public static void main(String[] args) {
AbstractApplicationContext context = new ClassPathXmlApplicationContext("app-conf.xml");
Animal animal=(Animal)context.getBean("animal");
System.out.println(animal.getName());
context.registerShutdownHook();
}
}
Inside post process before initialization: animal Inside init method Inside post process after initialization: animal Lion Inside destroy method
BeanPostProcessor with JavaConfig
Find the code to useBeanPostProcessor with JavaConfig.
MyBeanPostProcessor.java
package com.concretepage;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;
@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName)
throws BeansException {
System.out.println("Inside post process before initialization: "+beanName);
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException {
System.out.println("Inside post process after initialization: "+beanName);
return bean;
}
}
package com.concretepage;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import org.springframework.stereotype.Component;
@Component
public class ElephantService {
@PostConstruct
public void init() {
System.out.println("Inside init method");
}
public void print() {
System.out.println("Hello World!");
}
@PreDestroy
public void destroy() {
System.out.println("Inside destroy method");
}
}
package com.concretepage;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan(basePackages="com.concretepage")
public class AppConfig {
}
package com.concretepage;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class SpringDemo {
public static void main(String[] args) {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
ctx.register(AppConfig.class);
ctx.refresh();
ElephantService service = ctx.getBean(ElephantService.class);
service.print();
ctx.registerShutdownHook();
}
}
Inside post process before initialization: appConfig Inside post process after initialization: appConfig Inside post process before initialization: elephantService Inside init method Inside post process after initialization: elephantService Hello World! Inside destroy method
