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/*
* ============LICENSE_START=======================================================
* ONAP
* ================================================================================
* Copyright (C) 2019, 2021 AT&T Intellectual Property. 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.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.common.utils.services;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import lombok.AccessLevel;
import lombok.NoArgsConstructor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* This is a simple object registry, similar in spirit to JNDI, but suitable for use in a
* stand-alone JVM.
*/
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public class Registry {
private static final Logger logger = LoggerFactory.getLogger(Registry.class);
private static Registry instance = new Registry();
/**
* Registry map.
*/
private Map<String, Object> name2object = new ConcurrentHashMap<>();
/**
* Registers an object.
*
* @param name name by which the object is known
* @param object object to be registered
* @throws IllegalStateException if an object is already registered for that name
* @throws IllegalArgumentException if either argument is null
*/
public static void register(String name, Object object) {
if (name == null) {
throw new IllegalArgumentException("attempt to register: " + name);
}
if (object == null) {
throw new IllegalArgumentException("attempt to register null object for " + name);
}
instance.name2object.compute(name, (key, oldval) -> {
if (oldval != null) {
throw new IllegalStateException("already registered: " + name);
}
return object;
});
}
/**
* Registers an object, replacing any previously existing binding.
*
* @param name name by which the object is known
* @param object object to be registered
* @throws IllegalArgumentException if either argument is null
*/
public static void registerOrReplace(String name, Object object) {
if (name == null) {
throw new IllegalArgumentException("attempt to register: " + name);
}
if (object == null) {
throw new IllegalArgumentException("attempt to register null object for " + name);
}
instance.name2object.compute(name, (key, oldval) -> {
if (oldval != null) {
logger.warn("replacing previously registered: {}", name);
}
return object;
});
}
/**
* Unregisters an object.
*
* @param name name by which the object is known
* @return {@code true} if the object was unregistered, {@code false} if it did not
* exist
*/
public static boolean unregister(String name) {
return (instance.name2object.remove(name) != null);
}
/**
* Gets the object by the given name.
*
* @param name name of the object to get
* @return the object
* @throws IllegalArgumentException if no object is registered by the given name
*/
@SuppressWarnings("unchecked")
public static <T> T get(String name) {
Object obj = instance.name2object.get(name);
if (obj == null) {
throw new IllegalArgumentException("not registered: " + name);
}
return (T) obj;
}
/**
* Gets the object by the given name.
*
* @param name name of the object to get
* @param clazz object's class
* @return the object
* @throws IllegalArgumentException if no object is registered by the given name
*/
public static <T> T get(String name, Class<T> clazz) {
Object obj = instance.name2object.get(name);
if (obj == null) {
throw new IllegalArgumentException("not registered: " + name);
}
return clazz.cast(obj);
}
/**
* Gets the object by the given name, providing a default value if the name is not
* registered.
*
* @param name name of the object to get
* @param clazz object's class
* @param defaultVal the default value to return, if the object does not exist
* @return the object, if it exists, the default value, otherwise
*/
public static <T> T getOrDefault(String name, Class<T> clazz, T defaultVal) {
Object obj = instance.name2object.get(name);
return (obj != null ? clazz.cast(obj) : defaultVal);
}
/**
* Creates a new registry instance. This is typically only used by junit tests, as it
* discards any previous registry entries.
*/
public static void newRegistry() {
instance = new Registry();
}
}
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