geode-core/src/main/java/org/apache/geode/internal/cache/client/protocol/ClientProtocolServiceLoader.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF licenses this file to You 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 org.apache.geode.internal.cache.client.protocol;

import java.util.LinkedList;
import java.util.List;
import java.util.ServiceLoader;

import org.apache.geode.internal.cache.client.protocol.exception.ServiceLoadingFailureException;

public class ClientProtocolServiceLoader {
  private final List<ClientProtocolService> clientProtocolServices;

  public ClientProtocolServiceLoader() {
    clientProtocolServices = initializeProtocolServices();
  }

  private static List<ClientProtocolService> initializeProtocolServices() {
    List<ClientProtocolService> resultList = new LinkedList<>();
    for (ClientProtocolService clientProtocolService : ServiceLoader
        .load(ClientProtocolService.class)) {
      resultList.add(clientProtocolService);
    }

    return resultList;
  }

  public ClientProtocolService lookupService() {
    if (clientProtocolServices.isEmpty()) {
      throw new ServiceLoadingFailureException(
          "There is no ClientProtocolService implementation found in JVM");
    }

    if (clientProtocolServices.size() > 1) {
      throw new ServiceLoadingFailureException(
          "There is more than one ClientProtocolService implementation found in JVM; aborting");
    }
    ClientProtocolService clientProtocolService = clientProtocolServices.get(0);
    return clientProtocolService;
  }
}