https://jstobigdata.com/spring/spring-beanpostprocessor-to-customize-beans/

Author: Bikraji

pom.xml

@@ -13,6 +13,7 @@
     <module>spring-tutorial-bom</module>
     <module>spring-core-ioc</module>
     <module>spring-bean-lifecycle</module>
+    <module>spring-core-beanpostprocessor</module>
   </modules>
 
   <properties>

spring-core-beanpostprocessor/pom.xml

@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <parent>
+    <artifactId>spring-framework-tutorial-parent</artifactId>
+    <groupId>com.jstobigdata</groupId>
+    <version>1.0-SNAPSHOT</version>
+  </parent>
+  <modelVersion>4.0.0</modelVersion>
+
+  <artifactId>spring-core-beanpostprocessor</artifactId>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework</groupId>
+      <artifactId>spring-core</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.springframework</groupId>
+      <artifactId>spring-context</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>javax.annotation</groupId>
+      <artifactId>javax.annotation-api</artifactId>
+    </dependency>
+  </dependencies>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>com.jstobigdata</groupId>
+        <artifactId>spring-tutorial-boms</artifactId>
+        <type>pom</type>
+        <scope>import</scope>
+        <version>1.0-SNAPSHOT</version>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+</project>

spring-core-beanpostprocessor/src/main/java/core/bean/postprocessor/ExampleBean.java

@@ -0,0 +1,20 @@
+package core.bean.postprocessor;
+
+import org.springframework.stereotype.Component;
+
+import javax.annotation.PostConstruct;
+import javax.annotation.PreDestroy;
+
+@Component
+public class ExampleBean {
+
+  @PostConstruct
+  public void initData() {
+    System.out.println("Your custom initialization code goes here...");
+  }
+
+  @PreDestroy
+  public void clearData() {
+    System.out.println("Your custom destroy code goes here...");
+  }
+}

spring-core-beanpostprocessor/src/main/java/core/bean/postprocessor/ExampleConfig.java

@@ -0,0 +1,10 @@
+package core.bean.postprocessor;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("core.bean.postprocessor")
+public class ExampleConfig {
+  //Extra config goes
+}

spring-core-beanpostprocessor/src/main/java/core/bean/postprocessor/TestExampleBean.java

@@ -0,0 +1,16 @@
+package core.bean.postprocessor;
+
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+public class TestExampleBean {
+  public static void main(String[] args) {
+
+    ConfigurableApplicationContext context
+        = new AnnotationConfigApplicationContext(ExampleConfig.class);
+    context.getBean(ExampleBean.class);
+
+    //This is important
+    context.registerShutdownHook();
+  }
+}

spring-core-beanpostprocessor/src/main/java/core/bean/postprocessor/TraceBeanPostProcessor.java

@@ -0,0 +1,23 @@
+package core.bean.postprocessor;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanPostProcessor;
+import org.springframework.stereotype.Component;
+
+@Component
+public class TraceBeanPostProcessor implements BeanPostProcessor {
+
+  @Override
+  public Object postProcessBeforeInitialization(Object bean, String beanName)
+      throws BeansException {
+    System.out.println("Inside postProcessBeforeInitialization - " + beanName);
+    return bean;
+  }
+
+  @Override
+  public Object postProcessAfterInitialization(Object bean, String beanName)
+      throws BeansException {
+    System.out.println("Inside postProcessAfterInitialization - " + beanName);
+    return bean;
+  }
+}