BAEL-9294: Programmatic Bean Registration Mechanism with BeanRegistrar in Spring

spring-boot-modules/pom.xml

@@ -1,7 +1,7 @@
 <?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">
+         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>
     <groupId>com.baeldung.spring-boot-modules</groupId>
     <artifactId>spring-boot-modules</artifactId>
@@ -107,9 +107,11 @@
         <module>spring-boot-3-observation</module>
         <module>spring-boot-3-test-pitfalls</module>
         <module>spring-boot-3-testcontainers</module>
+        <module>spring-boot-3-url-matching</module>
         <module>spring-boot-3-2</module>
         <!-- <module>spring-boot-3-3</module> --> <!-- JAVA-42049 -->
         <module>spring-boot-3-4</module>
+        <module>spring-boot-4</module>
         <module>spring-boot-resilience4j</module>
         <module>spring-boot-properties</module>
         <module>spring-boot-properties-2</module>
@@ -122,7 +124,6 @@
         <module>spring-boot-springdoc-2</module>
         <module>spring-boot-ssl</module>
         <module>spring-boot-documentation</module>
-        <module>spring-boot-3-url-matching</module>
         <module>spring-boot-graalvm-docker</module>
         <module>spring-boot-validations</module>
         <module>spring-boot-openapi</module>

spring-boot-modules/spring-boot-4/pom.xml

@@ -0,0 +1,171 @@
+<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>spring-boot-4</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>spring-boot-4</name>
+    <description>Demo project for Spring Boot</description>
+
+    <parent>
+        <groupId>com.baeldung.spring-boot-modules</groupId>
+        <artifactId>spring-boot-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+<dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-devtools</artifactId>
+            <scope>runtime</scope>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-configuration-processor</artifactId>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.mapstruct</groupId>
+            <artifactId>mapstruct</artifactId>
+            <version>${mapstruct.version}</version>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+        </dependency>
+    </dependencies>
+
+    <profiles>
+        <profile>
+            <id>default</id>
+            <activation>
+                <activeByDefault>true</activeByDefault>
+            </activation>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.springframework.boot</groupId>
+                        <artifactId>spring-boot-maven-plugin</artifactId>
+                        <configuration>
+                            <mainClass>com.baeldung.virtualthreads.VirtualThreadsApp</mainClass>
+                            <excludes>
+                                <exclude>
+                                    <groupId>org.projectlombok</groupId>
+                                    <artifactId>lombok</artifactId>
+                                </exclude>
+                            </excludes>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+
+        <profile>
+            <id>integration</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-surefire-plugin</artifactId>
+                        <configuration>
+                            <!-- Force sequential test execution -->
+                            <parallel>none</parallel>
+                            <forkCount>1</forkCount>
+                            <reuseForks>false</reuseForks>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-compiler-plugin</artifactId>
+                    <configuration>
+                        <annotationProcessorPaths>
+                            <path>
+                                <groupId>org.mapstruct</groupId>
+                                <artifactId>mapstruct-processor</artifactId>
+                                <version>${mapstruct.version}</version>
+                            </path>
+                            <path>
+                                <groupId>org.projectlombok</groupId>
+                                <artifactId>lombok</artifactId>
+                                <version>${lombok.version}</version>
+                            </path>
+                            <!-- This is needed when using Lombok 1.18.16 and above -->
+                            <path>
+                                <groupId>org.projectlombok</groupId>
+                                <artifactId>lombok-mapstruct-binding</artifactId>
+                                <version>${lombok-mapstruct-binding.version}</version>
+                            </path>
+                        </annotationProcessorPaths>
+                    </configuration>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+
+    <repositories>
+        <repository>
+            <id>repository.spring.milestone</id>
+            <name>Spring Snapshot Repository</name>
+            <url>https://repo.spring.io/milestone</url>
+        </repository>
+        <repository>
+            <id>repository.spring.snapshot</id>
+            <name>Spring Snapshot Repository</name>
+            <url>https://repo.spring.io/snapshot</url>
+            <snapshots>
+                <enabled>true</enabled>
+                <updatePolicy>daily</updatePolicy>
+            </snapshots>
+        </repository>
+    </repositories>
+    <pluginRepositories>
+        <pluginRepository>
+            <id>repository.spring.milestone.plugins</id>
+            <name>Spring Snapshot Repository</name>
+            <url>https://repo.spring.io/milestone</url>
+        </pluginRepository>
+        <pluginRepository>
+            <id>repository.spring.snapshot.plugins</id>
+            <name>Spring Snapshot Repository</name>
+            <url>https://repo.spring.io/snapshot</url>
+            <snapshots>
+                <enabled>true</enabled>
+                <updatePolicy>daily</updatePolicy>
+            </snapshots>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <properties>
+        <mapstruct.version>1.6.3</mapstruct.version>
+        <spring-boot.version>4.0.0-SNAPSHOT</spring-boot.version>
+        <logback.version>1.5.18</logback.version>
+        <lombok-mapstruct-binding.version>0.2.0</lombok-mapstruct-binding.version>
+    </properties>
+
+</project>

spring-boot-modules/spring-boot-4/src/main/java/com/baeldung/spring/beanregistrar/BeanRegistrationsConfiguration.java

@@ -0,0 +1,26 @@
+package com.baeldung.spring.beanregistrar;
+
+import org.springframework.beans.factory.BeanRegistrar;
+import org.springframework.beans.factory.BeanRegistry;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.core.env.Environment;
+
+@ConditionalOnProperty(name = "application.registration-v7", havingValue = "true", matchIfMissing = true)
+@Configuration
+@Import(BeanRegistrationsConfiguration.MyBeanRegistrar.class)
+public class BeanRegistrationsConfiguration {
+
+    static class MyBeanRegistrar implements BeanRegistrar {
+
+        @Override
+        public void register(BeanRegistry registry, Environment env) {
+            registry.registerBean("myService", MyService.class);
+            registry.registerBean("service2", MyService.class, spec -> spec.prototype()
+                .lazyInit()
+                .primary());
+        }
+    }
+
+}

spring-boot-modules/spring-boot-4/src/main/java/com/baeldung/spring/beanregistrar/BeanRegistrationsSpring6Configuration.java

@@ -0,0 +1,37 @@
+package com.baeldung.spring.beanregistrar;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
+import org.springframework.beans.factory.support.GenericBeanDefinition;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@ConditionalOnProperty(name = "application.registration-v7", havingValue = "false")
+@SuppressWarnings("NullableProblems")
+@Configuration
+public class BeanRegistrationsSpring6Configuration {
+
+    @Bean
+    BeanDefinitionRegistryPostProcessor beanDefinitionRegistryPostProcessor() {
+        return new BeanDefinitionRegistryPostProcessor() {
+
+            @Override
+            public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
+                var beanDefinition = new GenericBeanDefinition();
+                beanDefinition.setBeanClass(MyService.class);
+                beanDefinition.setScope(BeanDefinition.SCOPE_SINGLETON);
+                registry.registerBeanDefinition("myService", beanDefinition);
+            }
+
+            @Override
+            public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+                // No-op
+            }
+        };
+    }
+
+}

spring-boot-modules/spring-boot-4/src/main/java/com/baeldung/spring/beanregistrar/MyService.java

@@ -0,0 +1,5 @@
+package com.baeldung.spring.beanregistrar;
+
+public class MyService {
+
+}

spring-boot-modules/spring-boot-4/src/main/java/com/baeldung/spring/beanregistrar/SampleApplication.java

@@ -0,0 +1,13 @@
+package com.baeldung.spring.beanregistrar;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SampleApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(SampleApplication.class, args);
+    }
+
+}

spring-boot-modules/spring-boot-4/src/test/java/com/baeldung/spring/beanregistrar/BeanRegistrarIntegrationTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.spring.beanregistrar;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class BeanRegistrarIntegrationTest {
+
+    @Autowired
+    MyService myService;
+
+    @Test
+    void whenRunningPlatform_thenRegisterBean() {
+        assertThat(myService).isNotNull();
+    }
+
+}

spring-boot-modules/spring-boot-4/src/test/java/com/baeldung/spring/beanregistrar/BeanRegistrationsSpring6IntegrationTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.spring.beanregistrar;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest(properties = "application.registration-v7=false")
+class BeanRegistrationsSpring6IntegrationTest {
+
+    @Autowired
+    MyService myService;
+
+    @Test
+    void whenRunningPlatform_thenRegisterBean() {
+        assertThat(myService).isNotNull();
+    }
+
+}