BAEL-3091: The Prototype Pattern in Java (changed code based on valid comments from a reader)

spring-boot-di/README.MD

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+## Spring Boot Dependency Inject
+
+This module contains articles about dependency injection with Spring Boot
+
+### The Course
+The "REST With Spring" Classes: http://bit.ly/restwithspring
+
+### Relevant Articles:
+
+- [Spring Component Scanning](https://www.baeldung.com/spring-component-scanning)

spring-boot-di/pom.xml

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+<?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">
+	<modelVersion>4.0.0</modelVersion>
+	<artifactId>spring-boot-di</artifactId>
+	<name>spring-boot-di</name>
+	<packaging>jar</packaging>
+	<description>Module For Spring Boot DI</description>
+
+	<parent>
+		<artifactId>parent-boot-2</artifactId>
+		<groupId>com.baeldung</groupId>
+		<version>0.0.1-SNAPSHOT</version>
+		<relativePath>../parent-boot-2</relativePath>
+	</parent>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.aspectj</groupId>
+			<artifactId>aspectjweaver</artifactId>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-tomcat</artifactId>
+			<scope>provided</scope>
+		</dependency>
+
+		<dependency>
+			<groupId>org.apache.tomcat.embed</groupId>
+			<artifactId>tomcat-embed-jasper</artifactId>
+			<scope>provided</scope>
+		</dependency>
+		<dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+				<configuration>
+					<mainClass>com.baeldung.SpringBootDiApplication</mainClass>
+					<layout>JAR</layout>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+
+	<properties>
+		<start-class>com.baeldung.SpringBootDiApplication</start-class>
+	</properties>
+
+</project>

spring-boot-di/src/main/java/com/baeldung/SpringBootDiApplication.java

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+package com.baeldung;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SpringBootDiApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(SpringBootDiApplication.class, args);
+    }
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/ExampleBean.java

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+package com.baeldung.componentscan;
+
+public class ExampleBean {
+
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/annotation/Animal.java

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+package com.baeldung.componentscan.filter.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+public @interface Animal {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/annotation/ComponentScanAnnotationFilterApp.java

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+package com.baeldung.componentscan.filter.annotation;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+
+@Configuration
+@ComponentScan(includeFilters = @ComponentScan.Filter(type = FilterType.ANNOTATION, classes = Animal.class))
+public class ComponentScanAnnotationFilterApp {
+
+    public static void main(String[] args) {
+    }
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/annotation/Elephant.java

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+package com.baeldung.componentscan.filter.annotation;
+
+@Animal
+public class Elephant {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/aspectj/Cat.java

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+package com.baeldung.componentscan.filter.aspectj;
+
+public class Cat {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/aspectj/ComponentScanAspectJFilterApp.java

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+package com.baeldung.componentscan.filter.aspectj;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+
+@Configuration
+@ComponentScan(includeFilters = @ComponentScan.Filter(type = FilterType.ASPECTJ,
+        pattern = "com.baeldung.componentscan.filter.aspectj.* "
+                + "&& !(com.baeldung.componentscan.filter.aspectj.L* "
+                + "|| com.baeldung.componentscan.filter.aspectj.C*)"))
+public class ComponentScanAspectJFilterApp {
+    public static void main(String[] args) {
+    }
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/aspectj/Elephant.java

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+package com.baeldung.componentscan.filter.aspectj;
+
+public class Elephant {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/aspectj/Loin.java

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+package com.baeldung.componentscan.filter.aspectj;
+
+public class Loin {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/assignable/Animal.java

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+package com.baeldung.componentscan.filter.assignable;
+
+public interface Animal {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/assignable/Cat.java

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+package com.baeldung.componentscan.filter.assignable;
+
+public class Cat implements Animal {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/assignable/ComponentScanAssignableTypeFilterApp.java

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+package com.baeldung.componentscan.filter.assignable;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+
+@Configuration
+@ComponentScan(includeFilters = @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, classes = Animal.class))
+public class ComponentScanAssignableTypeFilterApp {
+
+    public static void main(String[] args) {
+    }
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/assignable/Elephant.java

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+package com.baeldung.componentscan.filter.assignable;
+
+public class Elephant implements Animal {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/custom/Cat.java

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+package com.baeldung.componentscan.filter.custom;
+
+public class Cat {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/custom/ComponentScanCustomFilter.java

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+package com.baeldung.componentscan.filter.custom;
+
+import org.springframework.core.type.ClassMetadata;
+import org.springframework.core.type.classreading.MetadataReader;
+import org.springframework.core.type.classreading.MetadataReaderFactory;
+import org.springframework.core.type.filter.TypeFilter;
+
+import java.io.IOException;
+
+public class ComponentScanCustomFilter implements TypeFilter {
+
+    @Override
+    public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {
+        ClassMetadata classMetadata = metadataReader.getClassMetadata();
+        String fullyQualifiedName = classMetadata.getClassName();
+        String className = fullyQualifiedName.substring(fullyQualifiedName.lastIndexOf(".") + 1);
+        return className.length() > 5 ? true : false;
+    }
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/custom/ComponentScanCustomFilterApp.java

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+package com.baeldung.componentscan.filter.custom;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+
+@Configuration
+@ComponentScan(includeFilters = @ComponentScan.Filter(type = FilterType.CUSTOM, classes = ComponentScanCustomFilter.class))
+public class ComponentScanCustomFilterApp {
+
+    public static void main(String[] args) {
+    }
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/custom/Elephant.java

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+package com.baeldung.componentscan.filter.custom;
+
+public class Elephant {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/custom/Loin.java

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+package com.baeldung.componentscan.filter.custom;
+
+public class Loin {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/regex/Cat.java

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+package com.baeldung.componentscan.filter.regex;
+
+public class Cat {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/regex/ComponentScanRegexFilterApp.java

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+package com.baeldung.componentscan.filter.regex;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+
+@Configuration
+@ComponentScan(includeFilters = @ComponentScan.Filter(type = FilterType.REGEX, pattern = ".*(nt)"))
+public class ComponentScanRegexFilterApp {
+
+    public static void main(String[] args) {
+    }
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/regex/Elephant.java

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+package com.baeldung.componentscan.filter.regex;
+
+public class Elephant {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/filter/regex/Loin.java

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+package com.baeldung.componentscan.filter.regex;
+
+public class Loin {
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/springapp/SpringComponentScanApp.java

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+package com.baeldung.componentscan.springapp;
+
+import com.baeldung.componentscan.ExampleBean;
+
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan
+// @ComponentScan(excludeFilters = @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, value = Rose.class))
+// @ComponentScan(basePackages = "com.baeldung.componentscan.springapp")
+// @ComponentScan(basePackages = "com.baeldung.componentscan.springapp.animals")
+// @ComponentScan (excludeFilters = @ComponentScan.Filter(type=FilterType.REGEX,pattern="com\\.baeldung\\.componentscan\\.springapp\\.flowers\\..*"))
+public class SpringComponentScanApp {
+
+    private static ApplicationContext applicationContext;
+
+    @Bean
+    public ExampleBean exampleBean() {
+        return new ExampleBean();
+    }
+
+    public static void main(String[] args) {
+        applicationContext = new AnnotationConfigApplicationContext(SpringComponentScanApp.class);
+
+        for (String beanName : applicationContext.getBeanDefinitionNames()) {
+            System.out.println(beanName);
+        }
+    }
+
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/springapp/animals/Cat.java

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+package com.baeldung.componentscan.springapp.animals;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Cat {
+
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/springapp/animals/Dog.java

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+package com.baeldung.componentscan.springapp.animals;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Dog {
+
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/springapp/flowers/Rose.java

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+package com.baeldung.componentscan.springapp.flowers;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Rose {
+
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/springbootapp/SpringBootComponentScanApp.java

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+package com.baeldung.componentscan.springbootapp;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
+
+import com.baeldung.componentscan.ExampleBean;
+
+@SpringBootApplication
+// @ComponentScan(basePackages = "com.baeldung.componentscan.springbootapp.animals")
+// @ComponentScan ( excludeFilters = @ComponentScan.Filter(type=FilterType.REGEX,pattern="com\\.baeldung\\.componentscan\\.springbootapp\\.flowers\\..*"))
+// @ComponentScan(excludeFilters = @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE, value = Rose.class))
+
+public class SpringBootComponentScanApp {
+    private static ApplicationContext applicationContext;
+
+    @Bean
+    public ExampleBean exampleBean() {
+        return new ExampleBean();
+    }
+
+    public static void main(String[] args) {
+        applicationContext = SpringApplication.run(SpringBootComponentScanApp.class, args);
+        checkBeansPresence("cat", "dog", "rose", "exampleBean", "springBootApp");
+
+    }
+
+    private static void checkBeansPresence(String... beans) {
+        for (String beanName : beans) {
+            System.out.println("Is " + beanName + " in ApplicationContext: " + applicationContext.containsBean(beanName));
+        }
+    }
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/springbootapp/animals/Cat.java

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+package com.baeldung.componentscan.springbootapp.animals;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Cat {
+
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/springbootapp/animals/Dog.java

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+package com.baeldung.componentscan.springbootapp.animals;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Dog {
+
+}

spring-boot-di/src/main/java/com/baeldung/componentscan/springbootapp/flowers/Rose.java

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+package com.baeldung.componentscan.springbootapp.flowers;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Rose {
+
+}

spring-boot-di/src/test/java/com/baeldung/componentscan/filter/annotation/ComponentScanAnnotationFilterAppIntegrationTest.java

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+package com.baeldung.componentscan.filter.annotation;
+
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import static org.hamcrest.CoreMatchers.*;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = ComponentScanAnnotationFilterApp.class)
+public class ComponentScanAnnotationFilterAppIntegrationTest {
+
+    @Test
+    public void whenAnnotationFilterIsUsed_thenComponentScanShouldRegisterBeanAnnotatedWithAnimalAnootation() {
+        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(ComponentScanAnnotationFilterApp.class);
+        List<String> beans = Arrays.stream(applicationContext.getBeanDefinitionNames())
+            .filter(bean -> !bean.contains("org.springframework") && !bean.contains("componentScanAnnotationFilterApp"))
+            .collect(Collectors.toList());
+        assertThat(beans.size(), equalTo(1));
+        assertThat(beans.get(0), equalTo("elephant"));
+    }
+}

spring-boot-di/src/test/java/com/baeldung/componentscan/filter/aspectj/ComponentScanAspectJFilterAppIntegrationTest.java

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+package com.baeldung.componentscan.filter.aspectj;
+
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import static org.hamcrest.CoreMatchers.*;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = ComponentScanAspectJFilterApp.class)
+public class ComponentScanAspectJFilterAppIntegrationTest {
+
+    @Test
+    public void whenAspectJFilterIsUsed_thenComponentScanShouldRegisterBeanMatchingAspectJCreteria() {
+        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(ComponentScanAspectJFilterApp.class);
+        List<String> beans = Arrays.stream(applicationContext.getBeanDefinitionNames())
+            .filter(bean -> !bean.contains("org.springframework") && !bean.contains("componentScanAspectJFilterApp"))
+            .collect(Collectors.toList());
+        assertThat(beans.size(), equalTo(1));
+        assertThat(beans.get(0), equalTo("elephant"));
+    }
+}

spring-boot-di/src/test/java/com/baeldung/componentscan/filter/assignable/ComponentScanAssignableTypeFilterAppIntegrationTest.java

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+package com.baeldung.componentscan.filter.assignable;
+
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import static org.hamcrest.CoreMatchers.*;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = ComponentScanAssignableTypeFilterApp.class)
+public class ComponentScanAssignableTypeFilterAppIntegrationTest {
+
+    @Test
+    public void whenAssignableTypeFilterIsUsed_thenComponentScanShouldRegisterBeanOfAssignableTypeAndItsSubClass() {
+        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(ComponentScanAssignableTypeFilterApp.class);
+        List<String> beans = Arrays.stream(applicationContext.getBeanDefinitionNames())
+            .filter(bean -> !bean.contains("org.springframework") && !bean.contains("componentScanAssignableTypeFilterApp"))
+            .collect(Collectors.toList());
+        assertThat(beans.size(), equalTo(2));
+        assertThat(beans.contains("cat"), equalTo(true));
+        assertThat(beans.contains("elephant"), equalTo(true));
+    }
+}

spring-boot-di/src/test/java/com/baeldung/componentscan/filter/custom/ComponentScanCustomFilterAppIntegrationTest.java

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+package com.baeldung.componentscan.filter.custom;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.assertThat;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = ComponentScanCustomFilterApp.class)
+public class ComponentScanCustomFilterAppIntegrationTest {
+
+    @Test
+    public void whenCustomFilterIsUsed_thenComponentScanShouldRegisterBeanMatchingCustomFilter() {
+        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(ComponentScanCustomFilterApp.class);
+        List<String> beans = Arrays.stream(applicationContext.getBeanDefinitionNames())
+                .filter(bean -> !bean.contains("org.springframework") && !bean.contains("componentScanCustomFilterApp")
+                        && !bean.contains("componentScanCustomFilter"))
+                .collect(Collectors.toList());
+        assertThat(beans.size(), equalTo(1));
+        assertThat(beans.get(0), equalTo("elephant"));
+    }
+}

spring-boot-di/src/test/java/com/baeldung/componentscan/filter/regex/ComponentScanRegexFilterAppIntegrationTest.java

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+package com.baeldung.componentscan.filter.regex;
+
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.test.context.junit4.SpringRunner;
+import static org.hamcrest.CoreMatchers.*;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = ComponentScanRegexFilterApp.class)
+public class ComponentScanRegexFilterAppIntegrationTest {
+
+    @Test
+    public void whenRegexFilterIsUsed_thenComponentScanShouldRegisterBeanMatchingRegex() {
+        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(ComponentScanRegexFilterApp.class);
+        List<String> beans = Arrays.stream(applicationContext.getBeanDefinitionNames())
+            .filter(bean -> !bean.contains("org.springframework") && !bean.contains("componentScanRegexFilterApp"))
+            .collect(Collectors.toList());
+        assertThat(beans.size(), equalTo(1));
+        assertThat(beans.contains("elephant"), equalTo(true));
+    }
+}