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The bndlib project is a general library to be used with OSGi bundles. It contains lots of cool functionality that calculates dependencies, etc.
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/*
 * Copyright (c) OSGi Alliance (2011). All Rights Reserved.
 *
 * 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.osgi.service.component.annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Identify the annotated method as a {@code bind} method of a Service
 * Component.
 *
 * 
 * The annotated method is a bind method of the Component.
 *
 * 

 * This annotation is not processed at runtime by a Service Component Runtime
 * implementation. It must be processed by tools and used to add a Component
 * Description to the bundle.
 *
 * 

 * In the generated Component Description for a component, the references must
 * be ordered in ascending lexicographical order (using {@code String.compareTo}
 * ) of the reference {@link #name() name}s.
 *
 * @see "The reference element of a Component Description."
 * @version $Id: db97a1a46abf7de7ad8c0fe4f36a38d3782dd58c $
 */
@Retention(RetentionPolicy.CLASS)
@Target(ElementType.METHOD)
public @interface Reference {
	/**
	 * The name of this reference.
	 *
	 * 

	 * If not specified, the name of this reference is based upon the name of
	 * the method being annotated. If the method name begins with {@code bind},
	 * {@code set} or {@code add}, that is removed.
	 *
	 * @see "The name attribute of the reference element of a Component Description."
	 */
	String name() default "";

	/**
	 * The type of the service to bind to this reference.
	 *
	 * 

	 * If not specified, the type of the service to bind is based upon the type
	 * of the first argument of the method being annotated.
	 *
	 * @see "The interface attribute of the reference element of a Component Description."
	 */
	Class< ? > service() default Object.class;

	/**
	 * The cardinality of the reference.
	 *
	 * 

	 * If not specified, the reference has a
	 * {@link ReferenceCardinality#MANDATORY 1..1} cardinality.
	 *
	 * @see "The cardinality attribute of the reference element of a Component Description."
	 */
	ReferenceCardinality cardinality() default ReferenceCardinality.MANDATORY;

	/**
	 * The policy for the reference.
	 *
	 * 

	 * If not specified, the {@link ReferencePolicy#STATIC STATIC} reference
	 * policy is used.
	 *
	 * @see "The policy attribute of the reference element of a Component Description."
	 */
	ReferencePolicy policy() default ReferencePolicy.STATIC;

	/**
	 * The target filter for the reference.
	 *
	 * @see "The target attribute of the reference element of a Component Description."
	 */
	String target() default "";

	/**
	 * The name of the unbind method which is associated with the annotated bind
	 * method.
	 *
	 * 

	 * To declare no unbind method, the value {@code "-"} must be used.
	 *
	 * 

	 * If not specified, the name of the unbind method is derived from the name
	 * of the annotated bind method. If the annotated method name begins with
	 * {@code bind}, {@code set} or {@code add}, that is replaced with
	 * {@code unbind}, {@code unset} or {@code remove}, respectively, to derive
	 * the unbind method name. Otherwise, {@code un} is prefixed to the
	 * annotated method name to derive the unbind method name. The unbind method
	 * is only set if the component type contains a method with the derived
	 * name.
	 *
	 * @see "The unbind attribute of the reference element of a Component Description."
	 */
	String unbind() default "";

	/**
	 * The policy option for the reference.
	 *
	 * 

	 * If not specified, the {@link ReferencePolicyOption#RELUCTANT RELUCTANT}
	 * reference policy option is used.
	 *
	 * @see "The policy-option attribute of the reference element of a Component Description."
	 * @since 1.2
	 */
	ReferencePolicyOption policyOption() default ReferencePolicyOption.RELUCTANT;

	/**
	 * The name of the updated method which is associated with the annotated
	 * bind method.
	 * 
	 * 

	 * To declare no updated method, the value {@code "-"} must be used.
	 * 
	 * 
	 * If not specified, the name of the updated method is derived from the name
	 * of the annotated bind method. If the annotated method name begins with
	 * {@code bind}, {@code set} or {@code add}, that is replaced with
	 * {@code updated} to derive the updated method name. Otherwise,
	 * {@code updated} is prefixed to the annotated method name to derive the
	 * updated method name. The updated method is only set if the component type
	 * contains a method with the derived name.
	 * 
	 * @see "The updated attribute of the reference element of a Component Description."
	 * @since 1.2
	 */
	String updated() default "";
}