Ordering multiple BeanPostProcessor implementations example

In this post under Spring Core, I will show with example how to order multiple “BeanPostProcessor” interface implementations.

To order multiple “BeanPostProcessor” implementations, each implementations much implement “Ordered” interface and provide order number in the interface “getOrder” method.

Note: Ordering of “BeanPostProcessor” implementations only work with “@Component” annotation and not with “@Bean” annotation.

For our example, I will use the below “BeanPostProcessor” interface implementations

LogbackBeanPostProcessor

package core.package55;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.core.Ordered;
import org.springframework.core.PriorityOrdered;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Component
public class LogbackBeanPostProcessor implements BeanPostProcessor, Ordered {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("Logging by Logback before initialization of bean: " + beanName);
        return BeanPostProcessor.super.postProcessBeforeInitialization(bean, beanName);
    }
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("Logging by Logback after initialization of bean: " + beanName);
        return BeanPostProcessor.super.postProcessAfterInitialization(bean, beanName);
    }
    @Override
    public int getOrder() {
        return 1;
    }
}

Log4jBeanPostProcessor

package core.package55;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.core.Ordered;
import org.springframework.core.PriorityOrdered;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Component
public class Log4jBeanPostProcessor implements BeanPostProcessor, Ordered {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("Logging by Log4j before initialization of bean: " + beanName);
        return BeanPostProcessor.super.postProcessBeforeInitialization(bean, beanName);
    }
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("Logging by Log4j after initialization of bean: " + beanName);
        return BeanPostProcessor.super.postProcessAfterInitialization(bean, beanName);
    }
    @Override
    public int getOrder() {
        return 2;
    }
}

As you can see from the above code, both “BeanPostProcessor” implementations “Log4jBeanPostProcessor” and “LogbackBeanPostProcessor” implements “Ordered” interface and provide order number in “getOrder”
method. “Log4jBeanPostProcessor” return 2 in “getOrder” method, whereas “LogbackBeanPostProcessor” return 1 in “getOrder” method.

As a result, “LogbackBeanPostProcessor” is called first before “Log4jBeanPostProcessor” class.

Below are the classes to which “BeanPostProcessor” implementations are to be applied.

FileManager

package core.package55;
import org.springframework.stereotype.Component;
@Component
public class FileManager {
    public void upload(String fileName) {
        System.out.println("Uploading file with name: " + fileName);
    }
}

Main class

package core.package55;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan(basePackages = "core.package55")
public class Example55 {
    public static void main(String[] args) {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(Example55.class);
    }
}

Below is the output

Output

			
Logging by Logback before initialization of bean: example55
Logging by Log4j before initialization of bean: example55
Logging by Logback after initialization of bean: example55
Logging by Log4j after initialization of bean: example55
Logging by Logback before initialization of bean: fileManager
Logging by Log4j before initialization of bean: fileManager
Logging by Logback after initialization of bean: fileManager
Logging by Log4j after initialization of bean: fileManager

		

In this way we can order multiple “BeanPostProcessor” implementations.

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