GH-74 - Discover plugin registries automatically

core/src/main/java/org/springframework/plugin/core/config/PluginRegistriesBeanDefinitionRegistrar.java

@@ -29,6 +29,7 @@
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.plugin.core.OrderAwarePluginRegistry;
 import org.springframework.plugin.core.Plugin;
+import org.springframework.plugin.core.PluginRegistry;
 import org.springframework.plugin.core.support.PluginRegistryFactoryBean;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
@@ -39,6 +40,7 @@
  * to the bean definition for the factory.
  *
  * @author Oliver Gierke
+ * @author Gabriel Hall
  */
 public class PluginRegistriesBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
 
@@ -67,36 +69,46 @@ public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, B
 		}
 
 		for (Class<?> type : types) {
+			registerPluginRegistry(type, registry);
+		}
+	}
 
-			RootBeanDefinition beanDefinition = new RootBeanDefinition(PluginRegistryFactoryBean.class);
-			beanDefinition.setTargetType(getTargetType(type, OrderAwarePluginRegistry.class));
-			beanDefinition.getPropertyValues().addPropertyValue("type", type);
-
-			Qualifier annotation = type.getAnnotation(Qualifier.class);
+	/**
+	 * Registers a {@link PluginRegistryFactoryBean} for the given plugin type.
+	 *
+	 * @param type the plugin type to register.
+	 * @param registry the bean definition registry.
+	 */
+	public static void registerPluginRegistry(Class<?> type, BeanDefinitionRegistry registry) {
 
-			// If the plugin interface has a Qualifier annotation, propagate that to the bean definition of the registry
-			if (annotation != null) {
-				AutowireCandidateQualifier qualifierMetadata = new AutowireCandidateQualifier(Qualifier.class);
-				qualifierMetadata.setAttribute(AutowireCandidateQualifier.VALUE_KEY, annotation.value());
-				beanDefinition.addQualifier(qualifierMetadata);
-			}
+		RootBeanDefinition beanDefinition = new RootBeanDefinition(PluginRegistryFactoryBean.class);
+		beanDefinition.setTargetType(getTargetType(type, OrderAwarePluginRegistry.class));
+		beanDefinition.getPropertyValues().addPropertyValue("type", type);
 
-			// Default
-			String beanName = annotation == null //
-					? StringUtils.uncapitalize(type.getSimpleName() + "Registry") //
-					: annotation.value();
+		Qualifier annotation = type.getAnnotation(Qualifier.class);
 
-			registry.registerBeanDefinition(beanName, beanDefinition);
+		// If the plugin interface has a Qualifier annotation, propagate that to the bean definition of the registry
+		if (annotation != null) {
+			AutowireCandidateQualifier qualifierMetadata = new AutowireCandidateQualifier(Qualifier.class);
+			qualifierMetadata.setAttribute(AutowireCandidateQualifier.VALUE_KEY, annotation.value());
+			beanDefinition.addQualifier(qualifierMetadata);
 		}
+
+		String beanName = annotation == null //
+				? StringUtils.uncapitalize(type.getSimpleName() + "Registry") //
+				: annotation.value();
+
+		registry.registerBeanDefinition(beanName, beanDefinition);
 	}
 
 	/**
 	 * Returns the target type of the {@link PluginRegistry} for the given plugin type.
 	 *
-	 * @param pluginType must not be {@literal null}.
-	 * @return
+	 * @param pluginClass must not be {@literal null}.
+	 * @param wrapper the registry implementation type.
+	 * @return the registry target type.
 	 */
-	private static ResolvableType getTargetType(Class<?> pluginClass, Class<?> wrapper) {
+	public static ResolvableType getTargetType(Class<?> pluginClass, Class<?> wrapper) {
 
 		Assert.notNull(pluginClass, "Plugin type must not be null!");
 

pom.xml

@@ -40,6 +40,7 @@
 
 	<modules>
 		<module>core</module>
+		<module>spring-plugin-autoconfigure</module>
 	</modules>
 
 	<properties>
@@ -56,6 +57,7 @@
 		<slf4j.version>2.0.18</slf4j.version>
 
 		<artifactory-maven-plugin.version>3.7.0</artifactory-maven-plugin.version>
+		<spring-boot.version>4.2.0-M1</spring-boot.version>
 
 		<java-module-name>spring.plugin</java-module-name>
 	</properties>

spring-plugin-autoconfigure/pom.xml

@@ -0,0 +1,57 @@
+<?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/maven-v4_0_0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<artifactId>spring-plugin-autoconfigure</artifactId>
+
+	<name>Spring Plugin - Autoconfigure</name>
+	<description>Spring Boot auto-configuration for Spring Plugin</description>
+
+	<parent>
+		<groupId>org.springframework.plugin</groupId>
+		<artifactId>spring-plugin</artifactId>
+		<version>4.2.0-SNAPSHOT</version>
+	</parent>
+
+	<properties>
+		<java-module-name>spring.plugin.autoconfigure</java-module-name>
+	</properties>
+
+	<build>
+		<resources>
+			<resource>
+				<directory>src/main/resources</directory>
+				<filtering>true</filtering>
+			</resource>
+			<resource>
+				<directory>../src/main/resources</directory>
+				<filtering>true</filtering>
+				<targetPath>META-INF</targetPath>
+			</resource>
+		</resources>
+	</build>
+
+	<dependencies>
+
+		<dependency>
+			<groupId>org.springframework.plugin</groupId>
+			<artifactId>spring-plugin-core</artifactId>
+			<version>${project.version}</version>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-autoconfigure</artifactId>
+			<version>${spring-boot.version}</version>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-test</artifactId>
+			<version>${spring-boot.version}</version>
+			<scope>test</scope>
+		</dependency>
+
+	</dependencies>
+
+</project>

spring-plugin-autoconfigure/src/main/java/org/springframework/plugin/autoconfigure/PluginRegistriesAutoConfiguration.java

@@ -0,0 +1,124 @@
+/*
+ * Copyright 2026 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.plugin.autoconfigure;
+
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+import org.jspecify.annotations.Nullable;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.beans.factory.ListableBeanFactory;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
+import org.springframework.boot.autoconfigure.AutoConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.core.ResolvableType;
+import org.springframework.plugin.core.Plugin;
+import org.springframework.plugin.core.PluginRegistry;
+import org.springframework.plugin.core.config.PluginRegistriesBeanDefinitionRegistrar;
+
+/**
+ * Registers plugin registries for direct plugin interfaces implemented by Spring beans.
+ *
+ * @author Gabriel Hall
+ */
+@AutoConfiguration
+public final class PluginRegistriesAutoConfiguration {
+
+	@Bean
+	static PluginRegistryBeanDefinitionRegistrar pluginRegistryBeanDefinitionRegistrar() {
+		return new PluginRegistryBeanDefinitionRegistrar();
+	}
+
+	static final class PluginRegistryBeanDefinitionRegistrar
+			implements BeanDefinitionRegistryPostProcessor, BeanFactoryAware {
+
+		private @Nullable ListableBeanFactory beanFactory;
+
+		@Override
+		public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
+
+			ListableBeanFactory beanFactory = getBeanFactory();
+
+			for (Class<?> pluginType : getPluginTypes(beanFactory)) {
+				ResolvableType registryType = PluginRegistriesBeanDefinitionRegistrar.getTargetType(pluginType,
+						PluginRegistry.class);
+
+				if (beanFactory.getBeanNamesForType(registryType, true, false).length == 0) {
+					PluginRegistriesBeanDefinitionRegistrar.registerPluginRegistry(pluginType, registry);
+				}
+			}
+		}
+
+		@Override
+		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {}
+
+		@Override
+		public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
+			this.beanFactory = (ListableBeanFactory) beanFactory;
+		}
+
+		private static Set<Class<?>> getPluginTypes(ListableBeanFactory beanFactory) {
+
+			Set<Class<?>> result = new LinkedHashSet<>();
+
+			for (String beanName : beanFactory.getBeanNamesForType(Plugin.class, true, false)) {
+
+				Class<?> beanType = beanFactory.getType(beanName, false);
+
+				if (beanType != null) {
+					collectPluginTypes(beanType, result);
+				}
+			}
+
+			return result;
+		}
+
+		private ListableBeanFactory getBeanFactory() {
+
+			if (this.beanFactory == null) {
+				throw new IllegalStateException("No ListableBeanFactory configured!");
+			}
+
+			return this.beanFactory;
+		}
+
+		private static void collectPluginTypes(Class<?> type, Set<Class<?>> result) {
+
+			if (type.isInterface() && type != Plugin.class && Plugin.class.isAssignableFrom(type)) {
+				result.add(type);
+				return;
+			}
+
+			for (Class<?> candidate : type.getInterfaces()) {
+
+				if (candidate != Plugin.class && Plugin.class.isAssignableFrom(candidate)) {
+					result.add(candidate);
+				}
+			}
+
+			Class<?> superclass = type.getSuperclass();
+
+			if (superclass != null && superclass != Object.class) {
+				collectPluginTypes(superclass, result);
+			}
+		}
+	}
+}

spring-plugin-autoconfigure/src/main/java/org/springframework/plugin/autoconfigure/package-info.java

@@ -0,0 +1,5 @@
+/**
+ * Spring Boot auto-configuration for plugin registries.
+ */
+@org.jspecify.annotations.NullMarked
+package org.springframework.plugin.autoconfigure;

spring-plugin-autoconfigure/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -0,0 +1 @@
+org.springframework.plugin.autoconfigure.PluginRegistriesAutoConfiguration