com.alibaba.nacos.common.spi.NacosServiceLoader Maven / Gradle / Ivy
/*
* Copyright 1999-2018 Alibaba Group Holding Ltd.
*
* 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 com.alibaba.nacos.common.spi;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.ServiceLoader;
import java.util.concurrent.ConcurrentHashMap;
/**
* Nacos SPI Service Loader.
*
* @author xiweng.yy
*/
public class NacosServiceLoader {
private static final Map, Collection>> SERVICES = new ConcurrentHashMap<>();
/**
* Load service.
*
* Load service by SPI and cache the classes for reducing cost when load second time.
*
* @param service service class
* @param type of service
* @return service instances
*/
public static Collection load(final Class service) {
if (SERVICES.containsKey(service)) {
return newServiceInstances(service);
}
Collection result = new LinkedHashSet<>();
for (T each : ServiceLoader.load(service)) {
result.add(each);
cacheServiceClass(service, each);
}
return result;
}
private static void cacheServiceClass(final Class service, final T instance) {
if (!SERVICES.containsKey(service)) {
SERVICES.put(service, new LinkedHashSet<>());
}
SERVICES.get(service).add(instance.getClass());
}
/**
* New service instances.
*
* @param service service class
* @param type of service
* @return service instances
*/
public static Collection newServiceInstances(final Class service) {
return SERVICES.containsKey(service) ? newServiceInstancesFromCache(service) : Collections.emptyList();
}
@SuppressWarnings("unchecked")
private static Collection newServiceInstancesFromCache(Class service) {
Collection result = new LinkedHashSet<>();
for (Class each : SERVICES.get(service)) {
result.add((T) newServiceInstance(each));
}
return result;
}
private static Object newServiceInstance(final Class clazz) {
try {
return clazz.newInstance();
} catch (IllegalAccessException | InstantiationException e) {
throw new ServiceLoaderException(clazz, e);
}
}
}