ScopeCache.java

/*
 * Copyright 2002-2011 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.cloud.context.scope;

import java.util.Collection;

/**
 * A special purpose cache interface specifically for the {@link GenericScope} to use to manage cached bean instances.
 * Implementations generally fall into two categories: those that store values "globally" (i.e. one instance per key),
 * and those that store potentially multiple instances per key based on context (e.g. via a thread local). All
 * implementations should be thread safe.
 * 
 * @author Dave Syer
 * 
 */
public interface ScopeCache {

	/**
	 * Remove the object with this name from the cache.
	 * 
	 * @param name the object name
	 * @return the object removed or null if there was none
	 */
	Object remove(String name);

	/**
	 * Clear the cache and return all objects in an unmodifiable collection.
	 * 
	 * @return all objects stored in the cache
	 */
	Collection<Object> clear();

	/**
	 * Get the named object from the cache.
	 * 
	 * @param name the name of the object
	 * @return the object with that name or null if there is none
	 */
	Object get(String name);

	/**
	 * Put a value in the cache if the key is not already used. If one is already present with the name provided, it is
	 * not replaced, but is returned to the caller.
	 * 
	 * @param name the key
	 * @param value the new candidate value
	 * @return the value that is in the cache at the end of the operation
	 */
	Object put(String name, Object value);

}