差異處

這裏顯示兩個版本的差異處。

--- java:java:java8:concurrent:blockingoperationwithcompletablefuture:carefully_avoid_transition_task_of_callback [2019/01/13 18:35]
tony [How to resolve?]
+++ java:java:java8:concurrent:blockingoperationwithcompletablefuture:carefully_avoid_transition_task_of_callback [2023/06/25 09:48] (目前版本)
@@ 行 31: / 行 31: @@
 }
 </code>
+但假如你的使用情況像[[java:java:java8:concurrent:blockingoperationwithcompletablefuture:blocking_inside_cf|之前文章]]中，會將Blocking工作送到另外一個Thread，接著透過compose串接，就要考慮使用Async方式去延續工作:
+<code java>
+@Test
+public void testSendAsync(){
+	CompletableFuture<Response> sendAsync = CompletableFuture.supplyAsync(()->{
+		dumpCurrentThreadName("supplyAsync");
+		return launchTaskWithAuxThread(()->new BlockingJob().invoke());
+	}, es)
+	.thenCompose((CompletableFuture<Response> responseReceived)->{
+		dumpCurrentThreadName("thenCompose");
+		return responseReceived;
+	})
+	.thenApplyAsync((Response x)->{
+		dumpCurrentThreadName("thenApply");
+		return x;
+	}, es);
+	sendAsync.join();
+}
+</code>
+上面的是我在Java8上實做的範例。如果以作者的範例來說，可以參考我在Java11做的範例程式碼。它使用了一個共享的變數responseReceived；當Blocking工作結束後，使用responseReceived.completeAsync去串接thenApply，這樣可以讓工作的執行回到共用的ExecutorService:
+<code java>
+public static class BlockingJob2 {
+	private CompletableFuture<Response> responseReceived;
+	public BlockingJob2(CompletableFuture<Response> responseReceived) {
+		this.responseReceived = responseReceived;
+	}
+	public void invoke() {
+		try {
+			dumpCurrentThreadName("before blocking job");
+			Thread.sleep(2*1000);
+			// io blocking job and get response
+			responseReceived.completeAsync(()->new Response(), es);
+		} catch( Exception e ) {
+			// log
+		} finally {
+			dumpCurrentThreadName("after blocking job");
+		}
+	}
+}
+public static CompletableFuture<Response> send2(){
+	return CompletableFuture.supplyAsync(()->{
+		dumpCurrentThreadName("supplyAsync");
+		CompletableFuture<Response> responseReceived = new CompletableFuture<>();
+		launchTaskWithAuxThread(()->{
+			new BlockingJob2(responseReceived).invoke();
+		});
+		return responseReceived;
+	}, es)
+	.thenCompose((CompletableFuture<Response> responseReceived)->{
+		dumpCurrentThreadName("thenCompose");
+		return responseReceived;
+	})
+	.thenApply((Response x)->{
+		dumpCurrentThreadName("whenComplete: " + x.getClass().getName());
+		return x;
+	});
+}
+</code>
+async寫法帶來的是thread的控制性；sync則是因為減少context switch而帶來的則是較好的效能。要選擇哪一種方式，一定要先確定好你要的是什麼。
 ===== Reference =====
   * [[https://qconsf.com/sf2017/system/files/presentation-slides/cf.pdf|Asynchronous API with