[bs-142] Add @AssertMissingBean

Example usage is to fail fast if trying to provide
a @ConfigurationProperties bean and it was already
defined

[Fixes #50812235]

spring-bootstrap/src/main/java/org/springframework/bootstrap/context/annotation/AbstractOnBeanCondition.java

@@ -38,9 +38,19 @@ import org.springframework.util.MultiValueMap;
 abstract class AbstractOnBeanCondition implements Condition {
 
 	protected Log logger = LogFactory.getLog(getClass());
+	private List<String> beanClasses;
+	private List<String> beanNames;
 
 	protected abstract Class<?> annotationClass();
 
+	protected List<String> getBeanClasses() {
+		return this.beanClasses;
+	}
+
+	protected List<String> getBeanNames() {
+		return this.beanNames;
+	}
+
 	@Override
 	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
 
@@ -48,16 +58,16 @@ abstract class AbstractOnBeanCondition implements Condition {
 
 		MultiValueMap<String, Object> attributes = metadata.getAllAnnotationAttributes(
 				annotationClass().getName(), true);
-		List<String> beanClasses = collect(attributes, "value");
-		List<String> beanNames = collect(attributes, "name");
-		Assert.isTrue(beanClasses.size() > 0 || beanNames.size() > 0,
-				"@" + ClassUtils.getShortName(annotationClass())
-						+ " annotations must specify at least one bean");
+		this.beanClasses = collect(attributes, "value");
+		this.beanNames = collect(attributes, "name");
+		Assert.isTrue(this.beanClasses.size() > 0 || this.beanNames.size() > 0, "@"
+				+ ClassUtils.getShortName(annotationClass())
+				+ " annotations must specify at least one bean");
 
 		List<String> beanClassesFound = new ArrayList<String>();
 		List<String> beanNamesFound = new ArrayList<String>();
 
-		for (String beanClass : beanClasses) {
+		for (String beanClass : this.beanClasses) {
 			try {
 				// eagerInit set to false to prevent early instantiation (some
 				// factory beans will not be able to determine their object type at this
@@ -72,7 +82,7 @@ abstract class AbstractOnBeanCondition implements Condition {
 			} catch (ClassNotFoundException ex) {
 			}
 		}
-		for (String beanName : beanNames) {
+		for (String beanName : this.beanNames) {
 			if (context.getBeanFactory().containsBeanDefinition(beanName)) {
 				beanNamesFound.add(beanName);
 			}
@@ -80,9 +90,9 @@ abstract class AbstractOnBeanCondition implements Condition {
 
 		boolean result = evaluate(beanClassesFound, beanNamesFound);
 		if (this.logger.isDebugEnabled()) {
-			if (!beanClasses.isEmpty()) {
+			if (!this.beanClasses.isEmpty()) {
 				this.logger.debug(checking + "Looking for beans with class: "
-						+ beanClasses);
+						+ this.beanClasses);
 				if (beanClassesFound.isEmpty()) {
 					this.logger.debug(checking + "Found no beans");
 				} else {
@@ -91,9 +101,9 @@ abstract class AbstractOnBeanCondition implements Condition {
 				}
 			}
 
-			if (!beanNames.isEmpty()) {
-				this.logger
-						.debug(checking + "Looking for beans with names: " + beanNames);
+			if (!this.beanNames.isEmpty()) {
+				this.logger.debug(checking + "Looking for beans with names: "
+						+ this.beanNames);
 				if (beanNamesFound.isEmpty()) {
 					this.logger.debug(checking + "Found no beans");
 				} else {

spring-bootstrap/src/main/java/org/springframework/bootstrap/context/annotation/AssertMissingBean.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2012-2013 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
+ *
+ *      http://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.bootstrap.context.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Conditional;
+
+/**
+ * {@link Conditional} that only matches when the specified bean classes and/or names are
+ * not already contained in the {@link BeanFactory}, and throws an exception otherwise.
+ * 
+ * @author Dave Syer
+ */
+@Target({ ElementType.TYPE, ElementType.METHOD })
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Conditional(AssertMissingBeanCondition.class)
+public @interface AssertMissingBean {
+
+	/**
+	 * The class type of bean that should be checked. The condition matches when each
+	 * class specified is missing in the {@link ApplicationContext}.
+	 * @return the class types of beans to check
+	 */
+	Class<?>[] value() default {};
+
+	/**
+	 * The names of beans to check. The condition matches when each bean name specified is
+	 * missing in the {@link ApplicationContext}.
+	 * @return the name of beans to check
+	 */
+	String[] name() default {};
+
+}

spring-bootstrap/src/main/java/org/springframework/bootstrap/context/annotation/AssertMissingBeanCondition.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2012-2013 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
+ *
+ *      http://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.bootstrap.context.annotation;
+
+import org.springframework.beans.factory.BeanCreationException;
+import org.springframework.context.annotation.Condition;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+
+/**
+ * {@link Condition} that checks that specific beans are missing.
+ * 
+ * @author Dave Syer
+ * @see AssertMissingBean
+ */
+class AssertMissingBeanCondition extends OnMissingBeanCondition {
+
+	@Override
+	protected Class<?> annotationClass() {
+		return AssertMissingBean.class;
+	}
+
+	@Override
+	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
+		boolean result = super.matches(context, metadata);
+		if (!result) {
+			throw new BeanCreationException("Found existing bean for classes="
+					+ getBeanClasses() + " and names=" + getBeanNames());
+		}
+		return result;
+	}
+
+}

spring-bootstrap/src/test/java/org/springframework/bootstrap/context/annotation/EnableConfigurationPropertiesTests.java

@@ -15,13 +15,18 @@
  */
 package org.springframework.bootstrap.context.annotation;
 
+import java.util.Arrays;
+
 import javax.annotation.PostConstruct;
 
 import org.junit.Test;
+import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.bootstrap.TestUtils;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.ImportResource;
 import org.springframework.stereotype.Component;
 
 import static org.junit.Assert.assertEquals;
@@ -53,6 +58,45 @@ public class EnableConfigurationPropertiesTests {
 		assertEquals("foo", this.context.getBean(MoreProperties.class).getName());
 	}
 
+	@Test
+	public void testPropertiesBindingWithDefaultsInXml() {
+		this.context.register(TestConfiguration.class, DefaultXmlConfiguration.class);
+		this.context.refresh();
+		String[] beanNames = this.context.getBeanNamesForType(TestProperties.class);
+		assertEquals("Wrong beans: " + Arrays.asList(beanNames), 1, beanNames.length);
+		assertEquals("bar", this.context.getBean(TestProperties.class).getName());
+	}
+
+	@Test(expected = BeanCreationException.class)
+	public void testPropertiesBindingWithDefaultsInBeanMethodReverseOrder() {
+		this.context.register(TestBeanConfiguration.class, DefaultConfiguration.class);
+		this.context.refresh();
+		String[] beanNames = this.context.getBeanNamesForType(TestProperties.class);
+		assertEquals("Wrong beans: " + Arrays.asList(beanNames), 1, beanNames.length);
+		assertEquals("bar", this.context.getBean(TestProperties.class).getName());
+	}
+
+	@Test
+	public void testPropertiesBindingWithDefaultsInBeanMethod() {
+		this.context.register(DefaultConfiguration.class, TestBeanConfiguration.class);
+		this.context.refresh();
+		String[] beanNames = this.context.getBeanNamesForType(TestProperties.class);
+		assertEquals("Wrong beans: " + Arrays.asList(beanNames), 1, beanNames.length);
+		assertEquals("bar", this.context.getBean(TestProperties.class).getName());
+	}
+
+	// Maybe we could relax the condition that causes this exception but Spring makes it
+	// difficult because it is impossible for DefaultConfiguration to override a bean
+	// definition created with a direct regsistration (as opposed to a @Bean)
+	@Test(expected = BeanCreationException.class)
+	public void testPropertiesBindingWithDefaults() {
+		this.context.register(DefaultConfiguration.class, TestConfiguration.class);
+		this.context.refresh();
+		String[] beanNames = this.context.getBeanNamesForType(TestProperties.class);
+		assertEquals("Wrong beans: " + Arrays.asList(beanNames), 1, beanNames.length);
+		assertEquals("bar", this.context.getBean(TestProperties.class).getName());
+	}
+
 	@Test
 	public void testBindingWithTwoBeans() {
 		this.context.register(MoreConfiguration.class, TestConfiguration.class);
@@ -94,6 +138,32 @@ public class EnableConfigurationPropertiesTests {
 	protected static class TestConfiguration {
 	}
 
+	@Configuration
+	@EnableConfigurationProperties
+	protected static class TestBeanConfiguration {
+		@ConditionalOnMissingBean(TestProperties.class)
+		@Bean(name = "org.springframework.bootstrap.context.annotation.EnableConfigurationPropertiesTests$TestProperties")
+		public TestProperties testProperties() {
+			return new TestProperties();
+		}
+	}
+
+	@Configuration
+	protected static class DefaultConfiguration {
+		@Bean
+		@AssertMissingBean(TestProperties.class)
+		public TestProperties testProperties() {
+			TestProperties test = new TestProperties();
+			test.setName("bar");
+			return test;
+		}
+	}
+
+	@Configuration
+	@ImportResource("org/springframework/bootstrap/context/annotation/testProperties.xml")
+	protected static class DefaultXmlConfiguration {
+	}
+
 	@Component
 	protected static class TestConsumer {
 		@Autowired

spring-bootstrap/src/test/resources/org/springframework/bootstrap/context/annotation/testProperties.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
+
+	<bean
+		id="org.springframework.bootstrap.context.annotation.EnableConfigurationPropertiesTests$TestProperties"
+		class="org.springframework.bootstrap.context.annotation.EnableConfigurationPropertiesTests$TestProperties">
+		<property name="name" value="bar"/>
+	</bean>
+
+</beans>