14 - Futures with composition OMS
@backstreetbrogrammer
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Chapter 02 - Virtual Threads - Futures with composition OMS
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In Java, a thenCombine() method can be used to combine the results of two futures using a two-argument function.
CompletableFuture.completedFuture(new Order(request))
.thenCombine(orderValidateFuture, Order::validate)
.thenCombine(orderEnrichFuture, Order::enrich)
.thenCombine(orderPersistFuture, Order::persist)
.thenAccept(Order::sendToDownstream);
Time taken is same as before: 1 + max(1, 1, 1) + 1 = 3 seconds.
The handling thread creates a new order, as before, but wraps it in a future so that thenCombine can be called for validation, and then it calls again with the enrichment and persistence tasks.
Finally, a callback thenAccept() is used to send the order to downstream.
None of this code is blocking.
Pool threads jump from validation, enrichment and persistence tasks to order building and order sending, performing tasks as they become available, even across separate requests.
In this case, the only actual processing that the connection-handling thread performs is the building of a base order.
Github: https://github.com/backstreetbrogramm...
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