Is it possible to chain async calls using Guava?
Futures.chain
was removed in version 12.0
. The new method of chaining together ListenableFutures
is via the Futures.transform method.
https://github.com/google/guava/wiki/ListenableFutureExplained#application
From Guava latest javadoc (16.0.1
as of this writing).
ListenableFuture<RowKey> rowKeyFuture = indexService.lookUp(query);
AsyncFunction<RowKey, QueryResult> queryFunction =
new AsyncFunction<RowKey, QueryResult>() {
public ListenableFuture<QueryResult> apply(RowKey rowKey) {
return dataService.read(rowKey);
}
};
ListenableFuture<QueryResult> queryFuture = transform(rowKeyFuture, queryFunction);
You can use Futures.chain
for chaining ListenableFuture
s:
final ListeningExecutorService service1 = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(16));
final ListeningExecutorService service2 = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(16));
ListenableFuture<String> service1result = service1.submit(new Callable<String>() {
@Override
public String call() throws Exception {
return "service1result";
}
});
ListenableFuture<String> service2result = Futures.chain(service1result, new Function<String, ListenableFuture<String>>() {
@Override
public ListenableFuture<String> apply(final @Nullable String input) {
return service2.submit(new Callable<String>() {
@Override
public String call() throws Exception {
return Joiner.on(" -> ").join(input, "service2result");
}
});
}
});
System.out.format("Result: %s\r\n", service2result.get());
Output of at the code above in the terminal:
> run-main training.Training
[info] Compiling 1 Java source to /home/remeniuk/projects/guava-training/target/scala-2.9.1/classes...
[info] Running training.Training
Result: service1result -> service2result