/*-
 * ============LICENSE_START=======================================================
 * SDC
 * ================================================================================
 * 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.openecomp.core.logging.api;

import java.util.Iterator;
import java.util.ServiceLoader;

/**
 * Contains common functionality for factories used in the logging framework. <p>In order to use the
 * factory, a particular (e.g. framework-specific) implementation of a service must be configured as
 * described in <a href="http://docs.oracle.com/javase/8/docs/api/java/util/ServiceLoader.html">java.util.ServiceLoader</a>).</p>
 *
 * @see java.util.ServiceLoader
 */
public class BaseFactory {

  protected static <T> T locateService(Class<T> clazz) throws Exception {

    T service;
    ServiceLoader<T> loader = ServiceLoader.load(clazz);
    Iterator<T> iterator = loader.iterator();
    if (iterator.hasNext()) {

      service = iterator.next();
      if (iterator.hasNext()) {
        System.err.println(String.format("Warning! Configured more than one implementation of %s",
            clazz.getName()));
      }

      return service;
    }

    throw new IllegalArgumentException(
        (String.format("No implementations configured for %s", clazz.getName())));
  }
}