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Zeus Client

There is a newer version: 2.29.0

package io.contek.zeus.client.grpc;

import io.contek.zeus.client.ICloseableIterator;
import io.grpc.Context;
import io.grpc.StatusRuntimeException;

import javax.annotation.concurrent.NotThreadSafe;
import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.concurrent.Callable;

import static io.grpc.Context.CancellableContext;

@NotThreadSafe
public final class GrpcIterator implements ICloseableIterator {

  private final Iterator iterator;
  private final CancellableContext cancellableContext;

  public static  GrpcIterator fromCallable(Callable> callable) {
    CancellableContext cancellableContext = Context.current().withCancellation();
    Iterator streamingIterator;
    try {
      streamingIterator = cancellableContext.call(callable);
    } catch (Throwable t) {
      streamingIterator = Collections.emptyIterator();
    }
    return new GrpcIterator<>(streamingIterator, cancellableContext);
  }

  @Override
  public boolean hasNext() {
    try {
      return iterator.hasNext();
    } catch (StatusRuntimeException e) {
      return false;
    }
  }

  @Override
  public T next() {
    try {
      return iterator.next();
    } catch (StatusRuntimeException e) {
      throw new NoSuchElementException(e.getStatus().toString());
    }
  }

  @Override
  public void close() {
    cancellableContext.close();
  }

  private GrpcIterator(Iterator iterator, Context.CancellableContext context) {
    this.iterator = iterator;
    this.cancellableContext = context;
  }
}