com.google.api.gax.rpc

Class ServerStream<V>

java.lang.Object

com.google.api.gax.rpc.ServerStream<V>

Type Parameters:

V - The type of each response.

All Implemented Interfaces:

Iterable<V>

@BetaApi(value="The surface for streaming is not stable yet and may change in the future.")
public final class ServerStream<V>
extends Object
implements Iterable<V>

A blocking Iterable-style wrapper around server stream responses.

This class asynchronously pulls responses from upstream via StreamController.request(int) and exposes them via its Iterator. The implementation is back pressure aware and uses a constant buffer of 1 item.

Please note that the stream can only be consumed once and must either be fully consumed or be canceled.

Neither this class nor the iterator it returns is thread-safe.

Example usage:

 ServerStream<Item> stream = ...;

 for (Item item : stream) {
   System.out.println(item.id());

   // Allow for early termination
   if (item.id().equals("needle")) {
     // Cancelling the stream will cause `hasNext()` to return false on the next iteration,
     // naturally breaking the loop.
     stream.cancel();
   }
 }
 

Method Summary

Modifier and Type	Method and Description
void	cancel() Cleanly cancels a partially consumed stream.
boolean	isReady() Returns true if the next call to the iterator's hasNext() or next() is guaranteed to be nonblocking.
Iterator<V>	iterator()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Method Detail

iterator

@Nonnull
public Iterator<V> iterator()

Specified by:

iterator in interface Iterable<V>

isReady

public boolean isReady()

Returns true if the next call to the iterator's hasNext() or next() is guaranteed to be nonblocking.

Returns:

If the call on any of the iterator's methods is guaranteed to be nonblocking.

cancel

public void cancel()

Cleanly cancels a partially consumed stream. The associated iterator will return false for the hasNext() in the next iteration. This maintains the contract that an observed true from hasNext() will yield an item in next(), but afterwards will return false.