Merge pull request #8880 from vikasrajput6035/BAEL-3832

Bael 3832 : Difference between BeanFactory and ApplicationContext - First draft completed

spring-core-3/src/main/java/com/baeldung/ioccontainer/bean/CustomBeanFactoryPostProcessor.java

@@ -0,0 +1,21 @@
+package com.baeldung.ioccontainer.bean;
+
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+
+public class CustomBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
+    private static boolean isBeanFactoryPostProcessorRegistered = false;
+    
+    @Override
+    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory){
+        setBeanFactoryPostProcessorRegistered(true);
+    }
+
+    public static boolean isBeanFactoryPostProcessorRegistered() {
+        return isBeanFactoryPostProcessorRegistered;
+    }
+
+    public static void setBeanFactoryPostProcessorRegistered(boolean isBeanFactoryPostProcessorRegistered) {
+        CustomBeanFactoryPostProcessor.isBeanFactoryPostProcessorRegistered = isBeanFactoryPostProcessorRegistered;
+    }
+}

spring-core-3/src/main/java/com/baeldung/ioccontainer/bean/CustomBeanPostProcessor.java

@@ -0,0 +1,21 @@
+package com.baeldung.ioccontainer.bean;
+
+import org.springframework.beans.factory.config.BeanPostProcessor;
+
+public class CustomBeanPostProcessor implements BeanPostProcessor {
+    private static boolean isBeanPostProcessorRegistered = false;
+    
+    @Override
+    public Object postProcessBeforeInitialization(Object bean, String beanName){
+        setBeanPostProcessorRegistered(true);
+        return bean;
+    }
+
+    public static boolean isBeanPostProcessorRegistered() {
+        return isBeanPostProcessorRegistered;
+    }
+
+    public static void setBeanPostProcessorRegistered(boolean isBeanPostProcessorRegistered) {
+        CustomBeanPostProcessor.isBeanPostProcessorRegistered = isBeanPostProcessorRegistered;
+    }
+}

spring-core-3/src/main/java/com/baeldung/ioccontainer/bean/Student.java

@@ -0,0 +1,17 @@
+package com.baeldung.ioccontainer.bean;
+
+public class Student {
+    private static boolean isBeanInstantiated = false;
+
+    public void postConstruct() {
+        setBeanInstantiated(true);
+    }
+
+    public static boolean isBeanInstantiated() {
+        return isBeanInstantiated;
+    }
+
+    public static void setBeanInstantiated(boolean isBeanInstantiated) {
+        Student.isBeanInstantiated = isBeanInstantiated;
+    }
+}

spring-core-3/src/test/java/com/baeldung/ioccontainer/IOCContainerAppUnitTest.java

@@ -0,0 +1,86 @@
+package com.baeldung.ioccontainer;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.xml.XmlBeanFactory;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
+
+import com.baeldung.ioccontainer.bean.CustomBeanFactoryPostProcessor;
+import com.baeldung.ioccontainer.bean.CustomBeanPostProcessor;
+import com.baeldung.ioccontainer.bean.Student;
+
+public class IOCContainerAppUnitTest {
+
+    @BeforeEach
+    @AfterEach
+    public void resetInstantiationFlag() {
+        Student.setBeanInstantiated(false);
+        CustomBeanPostProcessor.setBeanPostProcessorRegistered(false);
+        CustomBeanFactoryPostProcessor.setBeanFactoryPostProcessorRegistered(false);
+    }
+
+    @Test
+    public void whenBFInitialized_thenStudentNotInitialized() {
+        Resource res = new ClassPathResource("ioc-container-difference-example.xml");
+        BeanFactory factory = new XmlBeanFactory(res);
+        
+        assertFalse(Student.isBeanInstantiated());
+    }
+
+    @Test
+    public void whenBFInitialized_thenStudentInitialized() {
+        Resource res = new ClassPathResource("ioc-container-difference-example.xml");
+        BeanFactory factory = new XmlBeanFactory(res);
+        Student student = (Student) factory.getBean("student");
+    
+        assertTrue(Student.isBeanInstantiated());
+    }
+    
+    @Test
+    public void whenAppContInitialized_thenStudentInitialized() {
+        ApplicationContext context = new ClassPathXmlApplicationContext("ioc-container-difference-example.xml");
+        
+        assertTrue(Student.isBeanInstantiated());
+    }
+
+    @Test
+    public void whenBFInitialized_thenBFPProcessorAndBPProcessorNotRegAutomatically() {
+        Resource res = new ClassPathResource("ioc-container-difference-example.xml");
+        ConfigurableListableBeanFactory factory = new XmlBeanFactory(res);
+
+        assertFalse(CustomBeanFactoryPostProcessor.isBeanFactoryPostProcessorRegistered());
+        assertFalse(CustomBeanPostProcessor.isBeanPostProcessorRegistered());
+    }
+
+    @Test
+    public void whenBFPostProcessorAndBPProcessorRegisteredManually_thenReturnTrue() {
+        Resource res = new ClassPathResource("ioc-container-difference-example.xml");
+        ConfigurableListableBeanFactory factory = new XmlBeanFactory(res);
+
+        CustomBeanFactoryPostProcessor beanFactoryPostProcessor = new CustomBeanFactoryPostProcessor();
+        beanFactoryPostProcessor.postProcessBeanFactory(factory);
+        assertTrue(CustomBeanFactoryPostProcessor.isBeanFactoryPostProcessorRegistered());
+
+        CustomBeanPostProcessor beanPostProcessor = new CustomBeanPostProcessor();
+        factory.addBeanPostProcessor(beanPostProcessor);
+        Student student = (Student) factory.getBean("student");
+        assertTrue(CustomBeanPostProcessor.isBeanPostProcessorRegistered());
+    }
+    
+    @Test
+    public void whenAppContInitialized_thenBFPostProcessorAndBPostProcessorRegisteredAutomatically() {
+        ApplicationContext context = new ClassPathXmlApplicationContext("ioc-container-difference-example.xml");
+
+        assertTrue(CustomBeanFactoryPostProcessor.isBeanFactoryPostProcessorRegistered());
+        assertTrue(CustomBeanPostProcessor.isBeanPostProcessorRegistered());
+    }
+}

spring-core-3/src/test/resources/ioc-container-difference-example.xml

@@ -0,0 +1,10 @@
+<?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-3.0.xsd">
+
+    <bean id="student" class="com.baeldung.ioccontainer.bean.Student" init-method="postConstruct"/>
+    <bean id="customBeanPostProcessor" class="com.baeldung.ioccontainer.bean.CustomBeanPostProcessor" />
+    <bean id="customBeanFactoryPostProcessor" class="com.baeldung.ioccontainer.bean.CustomBeanFactoryPostProcessor" />
+</beans>