SPR-5682: Initial support for ConfigurationClassApplicationContext

org.springframework.context/src/main/java/org/springframework/context/annotation/Bean.java

@@ -59,9 +59,11 @@ import org.springframework.beans.factory.annotation.Autowire;
  * @author Chris Beams
  * @since 3.0
  * @see Configuration
+ * @see DependsOn
  * @see Lazy
  * @see Primary
- * @see org.springframework.context.annotation.Scope
+ * @see Scope
+ * @see Value
  */
 @Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
 @Retention(RetentionPolicy.RUNTIME)

org.springframework.context/src/main/java/org/springframework/context/annotation/Configuration.java

@@ -17,6 +17,7 @@
 package org.springframework.context.annotation;
 
 import java.lang.annotation.Documented;
+
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -51,10 +52,11 @@ import org.springframework.stereotype.Component;
  * @author Rod Johnson
  * @author Chris Beams
  * @since 3.0
- * @see Bean
+ * @see Import
  * @see Lazy
- * @see Value
+ * @see Bean
  * @see ConfigurationClassPostProcessor;
+ * @see ConfigurationClassApplicationContext;
  */
 @Target({ElementType.TYPE})
 @Retention(RetentionPolicy.RUNTIME)
@@ -62,4 +64,19 @@ import org.springframework.stereotype.Component;
 @Component
 public @interface Configuration {
 
+	/**
+	 * Explicitly specify the name of the Spring bean definition associated
+	 * with this Configuration class.  If left unspecified (the common case),
+	 * a bean name will be automatically generated.
+	 * 
+	 * <p>The custom name applies only if the Configuration class is picked up via
+	 * component scanning or supplied directly to a {@link ConfigurationClassApplicationContext}.
+	 * If the Configuration class is registered as a traditional XML bean definition,
+	 * the name/id of the bean element will take precedence.
+	 * 
+	 * @return the specified bean name, if any
+	 * @see org.springframework.beans.factory.support.DefaultBeanNameGenerator
+	 */
+	String value() default "";
+	
 }

org.springframework.context/src/main/java/org/springframework/context/annotation/ConfigurationClassApplicationContext.java

@@ -0,0 +1,159 @@
+/*
+ * Copyright 2002-2009 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.context.annotation;
+
+import java.io.IOException;
+import java.util.LinkedHashSet;
+import java.util.Map;
+import java.util.Set;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.support.AbstractBeanDefinition;
+import org.springframework.beans.factory.support.BeanDefinitionBuilder;
+import org.springframework.beans.factory.support.DefaultBeanNameGenerator;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.context.support.AbstractRefreshableApplicationContext;
+import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+
+/**
+ * Standalone application context, accepting {@link Configuration}-annotated
+ * class literals as input. Useful for test harnesses or any other scenario
+ * where XML-based configuration is unnecessary or undesired.
+ *
+ * <p>In case of multiple Configuration classes, {@link Bean}
+ * methods defined in later classes will override those defined in earlier
+ * classes. This can be leveraged to deliberately override certain bean
+ * definitions via an extra Configuration class.
+ *
+ * @author Chris Beams
+ * @since 3.0
+ * @see Configuration
+ */
+public class ConfigurationClassApplicationContext extends AbstractRefreshableApplicationContext {
+
+	private final Set<Class<?>> configClasses = new LinkedHashSet<Class<?>>();
+
+	/**
+	 * Create a new {@link ConfigurationClassApplicationContext}, loading bean 
+	 * definitions from the given {@literal configClasses} and automatically
+	 * refreshing the context. <p>Note: if zero classes are specified, the
+	 * context will <b>not</b> be refreshed automatically, assuming that
+	 * the user will subsequently call {@link #addConfigurationClass(Class)}
+	 * and then manually refresh.
+	 * @param configClasses zero or more {@link Configuration} classes
+	 * @see #addConfigurationClass(Class)
+	 * @see #refresh()
+	 */
+	public ConfigurationClassApplicationContext(Class<?>... configClasses) {
+		if (configClasses.length == 0)
+			return;
+		
+		for (Class<?> configClass : configClasses) {
+			addConfigurationClass(configClass);
+		}
+		
+		this.refresh();
+	}
+	
+	/**
+	 * Add a {@link Configuration} class to be processed. Allows for programmatically
+	 * building a {@link ConfigurationClassApplicationContext}. Note that
+	 * {@link ConfigurationClassApplicationContext#refresh()} must be called in
+	 * order for the context to process the new class.  Calls to
+	 * {@link #addConfigurationClass(Class)} are idempotent; adding the same
+	 * Configuration class more than once has no additional effect.
+	 * @param configClass new Configuration class to be processed.
+	 * @see #ConfigurationClassApplicationContext(Class...)
+	 * @see #refresh()
+	 */
+	public void addConfigurationClass(Class<?> configClass) {
+		Assert.notNull(
+				AnnotationUtils.findAnnotation(configClass, Configuration.class),
+				"Class [" + configClass.getName() + "] is not annotated with @Configuration");
+		this.configClasses.add(configClass);
+	}
+
+	/**
+	 * Register a {@link BeanDefinition} for each {@link Configuration @Configuration}
+	 * class specified. Enables the default set of annotation configuration post
+	 * processors, such that {@literal @Autowired}, {@literal @Required}, and associated
+	 * annotations can be used within Configuration classes.
+	 * 
+	 * <p>Configuration class bean definitions are registered with generated bean definition names.
+	 * 
+	 * @see AnnotationConfigUtils#registerAnnotationConfigProcessors(org.springframework.beans.factory.support.BeanDefinitionRegistry)
+	 * @see ConfigurationClassPostProcessor
+	 */
+	@Override
+	protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory)
+			throws IOException, BeansException {
+		
+		// @Autowired and friends must be enabled by default when processing @Configuration classes
+		AnnotationConfigUtils.registerAnnotationConfigProcessors(beanFactory);
+		
+		for (Class<?> configClass : configClasses) {
+			AbstractBeanDefinition def = BeanDefinitionBuilder.rootBeanDefinition(configClass).getBeanDefinition();
+			
+			String name = AnnotationUtils.findAnnotation(configClass, Configuration.class).value();
+			if (!StringUtils.hasLength(name)) {
+				name = new DefaultBeanNameGenerator().generateBeanName(def, beanFactory);
+			}
+
+			beanFactory.registerBeanDefinition(name, def);
+		}
+		
+		new ConfigurationClassPostProcessor().postProcessBeanFactory(beanFactory);
+	}
+
+	/**
+	 * Return the bean instance that matches the given object type.
+	 * 
+	 * @param <T>
+	 * @param requiredType type the bean must match; can be an interface or superclass.
+	 * {@literal null} is disallowed.
+	 * @return bean matching required type
+	 * @throws NoSuchBeanDefinitionException if there is not exactly one matching bean
+	 * found
+	 * @see org.springframework.beans.factory.ListableBeanFactory#getBeansOfType(Class)
+	 * @see org.springframework.beans.factory.BeanFactory#getBean(String, Class)
+	 */
+	@SuppressWarnings("unchecked")
+	public <T> T getBean(Class<T> requiredType) {
+		Assert.notNull(requiredType, "requiredType may not be null");
+		
+		Map<String, ?> beansOfType = this.getBeansOfType(requiredType);
+		
+		switch (beansOfType.size()) {
+			case 0:
+				throw new NoSuchBeanDefinitionException(requiredType);
+			case 1:
+				return (T) beansOfType.values().iterator().next();
+			default:
+				throw new NoSuchBeanDefinitionException(requiredType,
+						beansOfType.size() + " matching bean definitions found " +
+						"(" + StringUtils.collectionToCommaDelimitedString(beansOfType.keySet()) + "). " +
+						"Consider qualifying with getBean(Class<T> beanType, String beanName) or " +
+						"declaring one bean definition as @Primary");
+		}
+	}
+
+}