GrpcDirectServerStreamingCallable.java

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package com.google.api.gax.grpc;

import com.google.api.gax.rpc.ApiCallContext;
import com.google.api.gax.rpc.ResponseObserver;
import com.google.api.gax.rpc.ServerStreamingCallable;
import com.google.api.gax.rpc.StreamController;
import com.google.common.base.Preconditions;
import io.grpc.ClientCall;
import io.grpc.MethodDescriptor;

/**
 * {@code GrpcDirectServerStreamingCallable} creates server-streaming gRPC calls.
 *
 * <p>In a chain of {@link ServerStreamingCallable}s this is the innermost callable. It wraps a
 * {@link ClientCall} in a {@link StreamController} and the downstream {@link ResponseObserver} in a
 * {@link ClientCall.Listener}. This forms a bidirectional bridge between gax & grpc. This is
 * implemented on top of {@link ClientCall.Listener} because {@link
 * io.grpc.stub.ClientResponseObserver} is currently marked as {@link io.grpc.ExperimentalApi}.
 *
 * <p>Package-private for internal use.
 */
class GrpcDirectServerStreamingCallable<RequestT, ResponseT>
    extends ServerStreamingCallable<RequestT, ResponseT> {
  private final MethodDescriptor<RequestT, ResponseT> descriptor;

  GrpcDirectServerStreamingCallable(MethodDescriptor<RequestT, ResponseT> descriptor) {
    this.descriptor = Preconditions.checkNotNull(descriptor);
  }

  @Override
  public void call(
      RequestT request, ResponseObserver<ResponseT> responseObserver, ApiCallContext context) {
    Preconditions.checkNotNull(request);
    Preconditions.checkNotNull(responseObserver);

    ClientCall<RequestT, ResponseT> call = GrpcClientCalls.newCall(descriptor, context);
    GrpcDirectStreamController<RequestT, ResponseT> controller =
        new GrpcDirectStreamController<>(call, responseObserver);
    controller.start(request);
  }
}