com.google.appengine.spi.FactoryProviderRegistry Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of runtime-impl-jetty12 Show documentation

There is a newer version: 2.0.31

/*
 * Copyright 2021 Google LLC
 *
 * 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
 *
 *     https://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.google.appengine.spi;

import com.google.common.collect.Maps;
import java.util.Collection;
import java.util.Map;

/**
 * Encapsulates a mapping from a base interface to {@link FactoryProvider} entities that return
 * instances implementing the aforementioned base interface. Since this class is not
 * thread-safe, clients should ensure proper synchronization.
 *
 */
class FactoryProviderRegistry {

  private Map, FactoryProvider> providerMap = Maps.newHashMap();

  FactoryProviderRegistry() {}

  /**
   * Register a provider for a given base interface. Will overwrite any previous mapping for that
   * interface.
   *
   * @param p the provider
   * @return The previous provider registered for a given base class (or null if there wasn't one).
   *
   */
   FactoryProvider register(FactoryProvider p) {
    return providerMap.put(p.getBaseInterface(), p);
  }

  /**
   * Get the provider for a given interface. N.B. this method has no notion of "subtypes"; the
   * passed interface must exactly match the base interface of a registered provider.
   *
   * @param baseInterface the caller wants a provider for.
   *
   */
   FactoryProvider getFactoryProvider(Class baseInterface) {
    // No type checking needed since the contract is enforced by FactoryProvider
    //
    @SuppressWarnings("unchecked")
    FactoryProvider p = (FactoryProvider) providerMap.get(baseInterface);
    return p;
  }

  /**
   * Get a view of the registered providers (see {@link HashMap#values()}).
   */
  Collection> getAllProviders() {
    return providerMap.values();
  }

}