Add post processor to register ProviderSettings @Bean

oauth2-authorization-server/src/main/java/org/springframework/security/config/annotation/web/configuration/OAuth2AuthorizationServerConfiguration.java

@@ -35,6 +35,7 @@
 import org.springframework.security.config.annotation.web.configurers.oauth2.server.resource.OAuth2ResourceServerConfigurer;
 import org.springframework.security.oauth2.jwt.JwtDecoder;
 import org.springframework.security.oauth2.jwt.NimbusJwtDecoder;
+import org.springframework.security.oauth2.server.authorization.config.ProviderSettings;
 import org.springframework.security.web.SecurityFilterChain;
 import org.springframework.security.web.util.matcher.RequestMatcher;
 
@@ -89,4 +90,11 @@ public static JwtDecoder jwtDecoder(JWKSource<SecurityContext> jwkSource) {
 		return new NimbusJwtDecoder(jwtProcessor);
 	}
 
+	@Bean
+	RegisterMissingBeanPostProcessor registerMissingBeanPostProcessor() {
+		RegisterMissingBeanPostProcessor postProcessor = new RegisterMissingBeanPostProcessor();
+		postProcessor.addBeanDefinition(ProviderSettings.class, () -> ProviderSettings.builder().build());
+		return postProcessor;
+	}
+
 }

oauth2-authorization-server/src/main/java/org/springframework/security/config/annotation/web/configuration/RegisterMissingBeanPostProcessor.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2020-2021 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.security.config.annotation.web.configuration;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Supplier;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.beans.factory.BeanFactoryUtils;
+import org.springframework.beans.factory.ListableBeanFactory;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.AbstractBeanDefinition;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.context.annotation.AnnotationBeanNameGenerator;
+
+/**
+ * Post processor to register one or more bean definitions on container initialization, if not already present.
+ *
+ * @author Steve Riesenberg
+ * @since 0.2.0
+ */
+final class RegisterMissingBeanPostProcessor implements BeanDefinitionRegistryPostProcessor, BeanFactoryAware {
+
+	private final AnnotationBeanNameGenerator beanNameGenerator = new AnnotationBeanNameGenerator();
+	private final List<AbstractBeanDefinition> beanDefinitions = new ArrayList<>();
+
+	private BeanFactory beanFactory;
+
+	@Override
+	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
+		for (AbstractBeanDefinition beanDefinition : this.beanDefinitions) {
+			String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
+					(ListableBeanFactory) this.beanFactory, beanDefinition.getBeanClass(), false, false);
+			if (beanNames.length == 0) {
+				String beanName = this.beanNameGenerator.generateBeanName(beanDefinition, registry);
+				registry.registerBeanDefinition(beanName, beanDefinition);
+			}
+		}
+	}
+
+	@Override
+	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+	}
+
+	<T> void addBeanDefinition(Class<T> beanClass, Supplier<T> beanSupplier) {
+		this.beanDefinitions.add(new RootBeanDefinition(beanClass, beanSupplier));
+	}
+
+	@Override
+	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
+		this.beanFactory = beanFactory;
+	}
+
+}

oauth2-authorization-server/src/test/java/org/springframework/security/config/annotation/web/configuration/RegisterMissingBeanPostProcessorTests.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2020-2021 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.security.config.annotation.web.configuration;
+
+import java.util.function.Supplier;
+
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.endsWith;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+
+/**
+ * Tests for {@link RegisterMissingBeanPostProcessor}.
+ *
+ * @author Steve Riesenberg
+ */
+public class RegisterMissingBeanPostProcessorTests {
+
+	private final RegisterMissingBeanPostProcessor postProcessor = new RegisterMissingBeanPostProcessor();
+
+	@Test
+	public void postProcessBeanDefinitionRegistryWhenClassAddedThenRegisteredWithClass() {
+		this.postProcessor.addBeanDefinition(SimpleBean.class, null);
+		this.postProcessor.setBeanFactory(new DefaultListableBeanFactory());
+
+		BeanDefinitionRegistry beanDefinitionRegistry = mock(BeanDefinitionRegistry.class);
+		this.postProcessor.postProcessBeanDefinitionRegistry(beanDefinitionRegistry);
+
+		ArgumentCaptor<BeanDefinition> beanDefinitionCaptor = ArgumentCaptor.forClass(BeanDefinition.class);
+		verify(beanDefinitionRegistry).registerBeanDefinition(endsWith("SimpleBean"), beanDefinitionCaptor.capture());
+
+		RootBeanDefinition beanDefinition = (RootBeanDefinition) beanDefinitionCaptor.getValue();
+		assertThat(beanDefinition.getBeanClass()).isEqualTo(SimpleBean.class);
+		assertThat(beanDefinition.getInstanceSupplier()).isNull();
+	}
+
+	@Test
+	public void postProcessBeanDefinitionRegistryWhenSupplierAddedThenRegisteredWithSupplier() {
+		Supplier<SimpleBean> beanSupplier = () -> new SimpleBean("string");
+		this.postProcessor.addBeanDefinition(SimpleBean.class, beanSupplier);
+		this.postProcessor.setBeanFactory(new DefaultListableBeanFactory());
+
+		BeanDefinitionRegistry beanDefinitionRegistry = mock(BeanDefinitionRegistry.class);
+		this.postProcessor.postProcessBeanDefinitionRegistry(beanDefinitionRegistry);
+
+		ArgumentCaptor<BeanDefinition> beanDefinitionCaptor = ArgumentCaptor.forClass(BeanDefinition.class);
+		verify(beanDefinitionRegistry).registerBeanDefinition(endsWith("SimpleBean"), beanDefinitionCaptor.capture());
+
+		RootBeanDefinition beanDefinition = (RootBeanDefinition) beanDefinitionCaptor.getValue();
+		assertThat(beanDefinition.getBeanClass()).isEqualTo(SimpleBean.class);
+		assertThat(beanDefinition.getInstanceSupplier()).isEqualTo(beanSupplier);
+	}
+
+	@Test
+	public void postProcessBeanDefinitionRegistryWhenNoBeanDefinitionsAddedThenNoneRegistered() {
+		this.postProcessor.setBeanFactory(new DefaultListableBeanFactory());
+
+		BeanDefinitionRegistry beanDefinitionRegistry = mock(BeanDefinitionRegistry.class);
+		this.postProcessor.postProcessBeanDefinitionRegistry(beanDefinitionRegistry);
+		verifyNoInteractions(beanDefinitionRegistry);
+	}
+
+	@Test
+	public void postProcessBeanDefinitionRegistryWhenBeanDefinitionAlreadyExistsThenNoneRegistered() {
+		this.postProcessor.addBeanDefinition(SimpleBean.class, null);
+		DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
+		beanFactory.registerBeanDefinition("simpleBean", new RootBeanDefinition(SimpleBean.class));
+		this.postProcessor.setBeanFactory(beanFactory);
+
+		BeanDefinitionRegistry beanDefinitionRegistry = mock(BeanDefinitionRegistry.class);
+		this.postProcessor.postProcessBeanDefinitionRegistry(beanDefinitionRegistry);
+		verifyNoInteractions(beanDefinitionRegistry);
+	}
+
+	private static final class SimpleBean {
+
+		private final String field;
+
+		private SimpleBean(String field) {
+			this.field = field;
+		}
+
+		public String getField() {
+			return field;
+		}
+
+	}
+
+}