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Get rid of the boilerplate code in Java properties based configuration.
/*
* Copyright (c) 2012-2015, Luigi R. Viggiano
* All rights reserved.
*
* This software is distributable under the BSD license.
* See the terms of the BSD license in the documentation provided with this software.
*/
package org.aeonbits.owner;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
/**
* Utility class caching Config instances that can be used as Singletons.
*
* This class is designed to be thread safe.
*
* @author Luigi R. Viggiano
* @since 1.0.6
*/
public final class ConfigCache {
private static final ConcurrentMap CACHE = new ConcurrentHashMap();
/** Don't let anyone instantiate this class */
private ConfigCache() {}
/**
* Gets from the cache or create, an instance of the given class using the given imports.
* The factory used to create new instances is the static {@link ConfigFactory#INSTANCE}.
*
* @param clazz the interface extending from {@link Config} that you want to instantiate.
* @param imports additional variables to be used to resolve the properties.
* @param type of the interface.
* @return an object implementing the given interface, that can be taken from the cache,
* which maps methods to property values.
*/
public static T getOrCreate(Class clazz, Map... imports) {
return getOrCreate(ConfigFactory.INSTANCE, clazz, clazz, imports);
}
/**
* Gets from the cache or create, an instance of the given class using the given imports.
*
* @param factory the factory to use to eventually create the instance.
* @param clazz the interface extending from {@link Config} that you want to instantiate.
* @param imports additional variables to be used to resolve the properties.
* @param type of the interface.
* @return an object implementing the given interface, that can be taken from the cache,
* which maps methods to property values.
*/
public static T getOrCreate(Factory factory, Class clazz, Map... imports) {
return getOrCreate(factory, clazz, clazz, imports);
}
/**
* Gets from the cache or create, an instance of the given class using the given imports.
* The factory used to create new instances is the static {@link ConfigFactory#INSTANCE}.
*
* @param key the key object to be used to identify the instance in the cache.
* @param clazz the interface extending from {@link Config} that you want to instantiate.
* @param imports additional variables to be used to resolve the properties.
* @param type of the interface.
* @return an object implementing the given interface, that can be taken from the cache,
* which maps methods to property values.
*/
public static T getOrCreate(Object key, Class clazz, Map... imports) {
return getOrCreate(ConfigFactory.INSTANCE, key, clazz, imports);
}
/**
* Gets from the cache or create, an instance of the given class using the given imports.
*
* @param factory the factory to use to eventually create the instance.
* @param key the key object to be used to identify the instance in the cache.
* @param clazz the interface extending from {@link Config} that you want to instantiate.
* @param imports additional variables to be used to resolve the properties.
* @param type of the interface.
* @return an object implementing the given interface, that can be taken from the cache,
* which maps methods to property values.
*/
public static T getOrCreate(Factory factory, Object key,
Class clazz, Map... imports) {
T existing = get(key);
if (existing != null) return existing;
T created = factory.create(clazz, imports);
T raced = add(key, created);
return raced != null ? raced : created;
}
/**
* Gets from the cache the {@link Config} instance identified by the given key.
*
* @param key the key object to be used to identify the instance in the cache.
* @param type of the interface.
* @return the {@link Config} object from the cache if exists, or null if it doesn't.
*/
@SuppressWarnings("unchecked")
public static T get(Object key) {
return (T) CACHE.get(key);
}
/**
* Adds a {@link Config} object into the cache.
*
* @param key the key object to be used to identify the instance in the cache.
* @param instance the instance of the {@link Config} object to be stored into the cache.
* @param type of the interface.
* @return the previous value associated with the specified key, or
* null if there was no mapping for the key.
*/
@SuppressWarnings("unchecked")
public static T add(Object key, T instance) {
return (T) CACHE.putIfAbsent(key, instance);
}
/**
* Removes all of the cached instances.
* The cache will be empty after this call returns.
*/
public static void clear() {
CACHE.clear();
}
/**
* Removes the cached instance for the given key if it is present.
*
* Returns previous instance associated to the given key in the cache,
* or null if the cache contained no instance for the given key.
*
*
The cache will not contain the instance for the specified key once the
* call returns.
*
* @param type of the interface.
* @param key key whose instance is to be removed from the cache.
* @return the previous instance associated with key, or
* null if there was no instance for key.
*/
@SuppressWarnings("unchecked")
public static T remove(Object key) {
return (T) CACHE.remove(key);
}
}