core/src/main/java/io/grpc/internal/AbstractServerImplBuilder.java

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 * modification, are permitted provided that the following conditions are
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 *    * Redistributions of source code must retain the above copyright
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 * in the documentation and/or other materials provided with the
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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package io.grpc.internal;

import static com.google.common.base.MoreObjects.firstNonNull;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.util.concurrent.MoreExecutors;
import com.google.instrumentation.stats.Stats;
import com.google.instrumentation.stats.StatsContextFactory;

import io.grpc.BindableService;
import io.grpc.CompressorRegistry;
import io.grpc.Context;
import io.grpc.DecompressorRegistry;
import io.grpc.HandlerRegistry;
import io.grpc.Internal;
import io.grpc.InternalNotifyOnServerBuild;
import io.grpc.ServerBuilder;
import io.grpc.ServerMethodDefinition;
import io.grpc.ServerServiceDefinition;
import io.grpc.ServerTransportFilter;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Executor;

import javax.annotation.Nullable;

/**
 * The base class for server builders.
 *
 * @param <T> The concrete type for this builder.
 */
public abstract class AbstractServerImplBuilder<T extends AbstractServerImplBuilder<T>>
        extends ServerBuilder<T> {

  private static final HandlerRegistry EMPTY_FALLBACK_REGISTRY = new HandlerRegistry() {
      @Override
      public List<ServerServiceDefinition> getServices() {
        return Collections.emptyList();
      }

      @Override
      public ServerMethodDefinition<?, ?> lookupMethod(String methodName,
          @Nullable String authority) {
        return null;
      }
    };

  private final InternalHandlerRegistry.Builder registryBuilder =
      new InternalHandlerRegistry.Builder();

  private final ArrayList<ServerTransportFilter> transportFilters =
      new ArrayList<ServerTransportFilter>();

  private final List<InternalNotifyOnServerBuild> notifyOnBuildList =
      new ArrayList<InternalNotifyOnServerBuild>();

  @Nullable
  private HandlerRegistry fallbackRegistry;

  @Nullable
  private Executor executor;

  @Nullable
  private DecompressorRegistry decompressorRegistry;

  @Nullable
  private CompressorRegistry compressorRegistry;

  @Nullable
  private StatsContextFactory statsFactory;

  @Override
  public final T directExecutor() {
    return executor(MoreExecutors.directExecutor());
  }

  @Override
  public final T executor(@Nullable Executor executor) {
    this.executor = executor;
    return thisT();
  }

  @Override
  public final T addService(ServerServiceDefinition service) {
    registryBuilder.addService(service);
    return thisT();
  }

  @Override
  public final T addService(BindableService bindableService) {
    if (bindableService instanceof InternalNotifyOnServerBuild) {
      notifyOnBuildList.add((InternalNotifyOnServerBuild) bindableService);
    }
    return addService(bindableService.bindService());
  }

  @Override
  public final T addTransportFilter(ServerTransportFilter filter) {
    transportFilters.add(checkNotNull(filter, "filter"));
    return thisT();
  }

  @Override
  public final T fallbackHandlerRegistry(HandlerRegistry registry) {
    this.fallbackRegistry = registry;
    return thisT();
  }

  @Override
  public final T decompressorRegistry(DecompressorRegistry registry) {
    decompressorRegistry = registry;
    return thisT();
  }

  @Override
  public final T compressorRegistry(CompressorRegistry registry) {
    compressorRegistry = registry;
    return thisT();
  }

  /**
   * Override the default stats implementation.
   */
  @VisibleForTesting
  protected T statsContextFactory(StatsContextFactory statsFactory) {
    this.statsFactory = statsFactory;
    return thisT();
  }

  @Override
  public ServerImpl build() {
    io.grpc.internal.InternalServer transportServer = buildTransportServer();
    ServerImpl server = new ServerImpl(getExecutorPool(),
        SharedResourcePool.forResource(GrpcUtil.TIMER_SERVICE), registryBuilder.build(),
        firstNonNull(fallbackRegistry, EMPTY_FALLBACK_REGISTRY), transportServer,
        Context.ROOT, firstNonNull(decompressorRegistry, DecompressorRegistry.getDefaultInstance()),
        firstNonNull(compressorRegistry, CompressorRegistry.getDefaultInstance()),
        transportFilters,
        firstNonNull(statsFactory,
            firstNonNull(Stats.getStatsContextFactory(), NoopStatsContextFactory.INSTANCE)),
        GrpcUtil.STOPWATCH_SUPPLIER);
    for (InternalNotifyOnServerBuild notifyTarget : notifyOnBuildList) {
      notifyTarget.notifyOnBuild(server);
    }
    return server;
  }

  private ObjectPool<? extends Executor> getExecutorPool() {
    final Executor savedExecutor = executor;
    if (savedExecutor == null) {
      return SharedResourcePool.forResource(GrpcUtil.SHARED_CHANNEL_EXECUTOR);
    }
    return new ObjectPool<Executor>() {
      @Override
      public Executor getObject() {
        return savedExecutor;
      }

      @Override
      public Executor returnObject(Object object) {
        return null;
      }
    };
  }

  /**
   * Children of AbstractServerBuilder should override this method to provide transport specific
   * information for the server.  This method is mean for Transport implementors and should not be
   * used by normal users.
   */
  @Internal
  protected abstract io.grpc.internal.InternalServer buildTransportServer();

  private T thisT() {
    @SuppressWarnings("unchecked")
    T thisT = (T) this;
    return thisT;
  }
}