Add support for annotation scan in @ConditionalOn*Bean

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionalOnBean.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.autoconfigure.condition;
 
+import java.lang.annotation.Annotation;
 import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
@@ -45,6 +46,13 @@ public @interface ConditionalOnBean {
 	 */
 	Class<?>[] value() default {};
 
+	/**
+	 * The annotation type decorating a bean that should be checked. The condition matches
+	 * when each class specified is missing from beans in the {@link ApplicationContext}.
+	 * @return the class types of beans to check
+	 */
+	Class<? extends Annotation>[] annotation() default {};
+
 	/**
 	 * The names of beans to check. The condition matches when any of the bean names
 	 * specified is contained in the {@link ApplicationContext}.

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionalOnMissingBean.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.autoconfigure.condition;
 
+import java.lang.annotation.Annotation;
 import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
@@ -45,6 +46,14 @@ public @interface ConditionalOnMissingBean {
 	 */
 	Class<?>[] value() default {};
 
+	/**
+	 * The annotation type decorating a bean that should be checked. The condition matches
+	 * when each class specified is missing from all beans in the
+	 * {@link ApplicationContext}.
+	 * @return the class types of beans to check
+	 */
+	Class<? extends Annotation>[] annotation() default {};
+
 	/**
 	 * The names of beans to check. The condition matches when each bean name specified is
 	 * missing in the {@link ApplicationContext}.

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnBeanCondition.java

@@ -16,10 +16,12 @@
 
 package org.springframework.boot.autoconfigure.condition;
 
+import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryUtils;
@@ -36,6 +38,7 @@ import org.springframework.util.ClassUtils;
 import org.springframework.util.MultiValueMap;
 import org.springframework.util.ReflectionUtils;
 import org.springframework.util.ReflectionUtils.MethodCallback;
+import org.springframework.util.StringUtils;
 
 /**
  * {@link Condition} that checks for the presence or absence of specific beans.
@@ -96,6 +99,11 @@ class OnBeanCondition extends SpringBootCondition implements ConfigurationCondit
 					context.getClassLoader(), considerHierarchy)));
 		}
 
+		for (String annotation : beans.getAnnotations()) {
+			beanNames.addAll(Arrays.asList(getBeanNamesForAnnotation(beanFactory,
+					annotation, context.getClassLoader(), considerHierarchy)));
+		}
+
 		for (String beanName : beans.getNames()) {
 			if (containsBean(beanFactory, beanName, considerHierarchy)) {
 				beanNames.add(beanName);
@@ -132,10 +140,45 @@ class OnBeanCondition extends SpringBootCondition implements ConfigurationCondit
 		}
 	}
 
+	private String[] getBeanNamesForAnnotation(
+			ConfigurableListableBeanFactory beanFactory, String type,
+			ClassLoader classLoader, boolean considerHierarchy) throws LinkageError {
+		String[] result = NO_BEANS;
+		try {
+			@SuppressWarnings("unchecked")
+			Class<? extends Annotation> typeClass = (Class<? extends Annotation>) ClassUtils
+					.forName(type, classLoader);
+			Map<String, Object> annotated = beanFactory.getBeansWithAnnotation(typeClass);
+			result = annotated.keySet().toArray(new String[annotated.size()]);
+			if (considerHierarchy) {
+				if (beanFactory.getParentBeanFactory() instanceof ConfigurableListableBeanFactory) {
+					String[] parentResult = getBeanNamesForAnnotation(
+							(ConfigurableListableBeanFactory) beanFactory
+									.getParentBeanFactory(),
+							type, classLoader, true);
+					List<String> resultList = new ArrayList<String>();
+					resultList.addAll(Arrays.asList(result));
+					for (String beanName : parentResult) {
+						if (!resultList.contains(beanName)
+								&& !beanFactory.containsLocalBean(beanName)) {
+							resultList.add(beanName);
+						}
+					}
+					result = StringUtils.toStringArray(resultList);
+				}
+			}
+			return result;
+		}
+		catch (ClassNotFoundException ex) {
+			return NO_BEANS;
+		}
+	}
+
 	private static class BeanSearchSpec {
 
 		private List<String> names = new ArrayList<String>();
 		private List<String> types = new ArrayList<String>();
+		private List<String> annotations = new ArrayList<String>();
 		private SearchStrategy strategy;
 
 		public BeanSearchSpec(ConditionContext context, AnnotatedTypeMetadata metadata,
@@ -144,12 +187,16 @@ class OnBeanCondition extends SpringBootCondition implements ConfigurationCondit
 					.getAllAnnotationAttributes(annotationType.getName(), true);
 			collect(attributes, "name", this.names);
 			collect(attributes, "value", this.types);
+			collect(attributes, "annotation", this.annotations);
 			if (this.types.isEmpty() && this.names.isEmpty()) {
 				addDeducedBeanType(context, metadata, this.types);
 			}
-			Assert.isTrue(!this.types.isEmpty() || !this.names.isEmpty(), "@"
-					+ ClassUtils.getShortName(annotationType)
-					+ " annotations must specify at least one bean");
+			Assert.isTrue(
+					!this.types.isEmpty() || !this.names.isEmpty()
+							|| !this.annotations.isEmpty(),
+					"@"
+							+ ClassUtils.getShortName(annotationType)
+							+ " annotations must specify at least one bean (type, name or annotation)");
 			this.strategy = (SearchStrategy) metadata.getAnnotationAttributes(
 					annotationType.getName()).get("search");
 		}
@@ -204,6 +251,10 @@ class OnBeanCondition extends SpringBootCondition implements ConfigurationCondit
 			return this.types;
 		}
 
+		public List<String> getAnnotations() {
+			return this.annotations;
+		}
+
 		@Override
 		public String toString() {
 			return new ToStringCreator(this).append("names", this.names)

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnBeanTests.java

@@ -23,6 +23,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.ImportResource;
+import org.springframework.scheduling.annotation.EnableScheduling;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -32,6 +33,7 @@ import static org.junit.Assert.assertTrue;
  * 
  * @author Dave Syer
  */
+// FIXME: unignore test
 @Ignore
 public class ConditionalOnBeanTests {
 
@@ -77,6 +79,14 @@ public class ConditionalOnBeanTests {
 		assertEquals("bar", this.context.getBean("bar"));
 	}
 
+	@Test
+	public void testAnnotationOnBeanCondition() {
+		this.context.register(FooConfiguration.class, OnAnnotationConfiguration.class);
+		this.context.refresh();
+		assertTrue(this.context.containsBean("bar"));
+		assertEquals("bar", this.context.getBean("bar"));
+	}
+
 	@Configuration
 	@ConditionalOnBean(name = "foo")
 	protected static class OnBeanNameConfiguration {
@@ -86,6 +96,15 @@ public class ConditionalOnBeanTests {
 		}
 	}
 
+	@Configuration
+	@ConditionalOnBean(annotation = EnableScheduling.class)
+	protected static class OnAnnotationConfiguration {
+		@Bean
+		public String bar() {
+			return "bar";
+		}
+	}
+
 	@Configuration
 	@ConditionalOnBean(String.class)
 	protected static class OnBeanClassConfiguration {
@@ -96,6 +115,7 @@ public class ConditionalOnBeanTests {
 	}
 
 	@Configuration
+	@EnableScheduling
 	protected static class FooConfiguration {
 		@Bean
 		public String foo() {

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnMissingBeanTests.java

@@ -20,6 +20,7 @@ import org.junit.Test;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.annotation.EnableScheduling;
 
 import static org.hamcrest.Matchers.equalTo;
 import static org.junit.Assert.assertEquals;
@@ -84,6 +85,14 @@ public class ConditionalOnMissingBeanTests {
 		assertThat(this.context.getBeansOfType(ExampleBean.class).size(), equalTo(1));
 	}
 
+	@Test
+	public void testAnnotationOnMissingBeanCondition() {
+		this.context.register(FooConfiguration.class, OnAnnotationConfiguration.class);
+		this.context.refresh();
+		assertFalse(this.context.containsBean("bar"));
+		assertEquals("foo", this.context.getBean("foo"));
+	}
+
 	@Configuration
 	@ConditionalOnMissingBean(name = "foo")
 	protected static class OnBeanNameConfiguration {
@@ -94,6 +103,16 @@ public class ConditionalOnMissingBeanTests {
 	}
 
 	@Configuration
+	@ConditionalOnMissingBean(annotation = EnableScheduling.class)
+	protected static class OnAnnotationConfiguration {
+		@Bean
+		public String bar() {
+			return "bar";
+		}
+	}
+
+	@Configuration
+	@EnableScheduling
 	protected static class FooConfiguration {
 		@Bean
 		public String foo() {