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/*-
* ============LICENSE_START=======================================================
* ONAP - SO
* ================================================================================
* Copyright (C) 2017 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.so.client;
import java.util.Iterator;
import java.util.ServiceLoader;
public class RestPropertiesLoader {
/* required to make ServiceLoader thread safe */
private static final ThreadLocal<ServiceLoader<RestProperties>> services =
new ThreadLocal<ServiceLoader<RestProperties>>() {
@Override
protected ServiceLoader<RestProperties> initialValue() {
return ServiceLoader.load(RestProperties.class);
}
};
private RestPropertiesLoader() {}
private static class Helper {
private static final RestPropertiesLoader INSTANCE = new RestPropertiesLoader();
}
public static RestPropertiesLoader getInstance() {
return Helper.INSTANCE;
}
public <T> T getNewImpl(Class<? extends RestProperties> clazz) {
return this.getImpl(clazz, true);
}
public <T> T getImpl(Class<? extends RestProperties> clazz) {
return this.getImpl(clazz, false);
}
private <T> T getImpl(Class<? extends RestProperties> clazz, boolean forceNewInstance) {
T result = null;
ServiceLoader<RestProperties> loader = this.services.get();
Iterator<RestProperties> propertyImpls = loader.iterator();
RestProperties item;
while (propertyImpls.hasNext()) {
item = propertyImpls.next();
if (clazz.isAssignableFrom(item.getClass())) {
try {
if (forceNewInstance) {
result = (T) item.getClass().newInstance();
} else {
result = (T) item;
}
} catch (InstantiationException | IllegalAccessException e) {
/*
* all spi implementations must provide a public no argument constructor
*/
}
// break;
}
}
return result;
}
}
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