Configuration.java

/*
 * 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.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.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

/**
 * Indicates that a class declares one or more {@link Bean} methods and may be processed
 * by the Spring container to generate bean definitions and service requests for those beans
 * at runtime.
 *
 * <p>Configuration is meta-annotated as a {@link Component}, therefore Configuration
 * classes are candidates for component-scanning and may also take advantage of
 * {@link Autowired} at the field and method but not at the constructor level.
 * Externalized values may be wired into Configuration classes using the {@link Value}
 * annotation.
 *
 * <p>May be used in conjunction with the {@link Lazy} annotation to indicate that all Bean
 * methods declared within this class are by default lazily initialized.
 *
 * <h3>Constraints</h3>
 * <ul>
 *    <li>Configuration classes must be non-final
 *    <li>Configuration classes must be non-local (may not be declared within a method)
 *    <li>Configuration classes must have a default/no-arg constructor and may not use
 *        {@link Autowired} constructor parameters
 * </ul>
 *
 * @author Rod Johnson
 * @author Chris Beams
 * @since 3.0
 * @see Import
 * @see Lazy
 * @see Bean
 * @see ConfigurationClassPostProcessor
 * @see AnnotationConfigApplicationContext
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@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 AnnotationConfigApplicationContext}.
	 * 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 "";

}