BAEL-7713 - add example merging async services response (#16280)

* BAEL-7713 - add example merging async services response

* BAEL-7713 update test class naming convention

spring-scheduling/src/main/java/com/baeldung/async/AsyncService.java

@@ -0,0 +1,23 @@
+package com.baeldung.async;
+
+import java.util.concurrent.CompletableFuture;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+@Service
+public class AsyncService {
+
+    @Autowired
+    private FirstAsyncService fisrtService;
+    @Autowired
+    private SecondAsyncService secondService;
+
+    public CompletableFuture<String> asyncMergeServicesResponse() throws InterruptedException {
+        CompletableFuture<String> fisrtServiceResponse = fisrtService.asyncGetData();
+        CompletableFuture<String> secondServiceResponse = secondService.asyncGetData();
+
+        // Merge responses from FirstAsyncService and SecondAsyncService
+        return fisrtServiceResponse.thenCompose(fisrtServiceValue -> secondServiceResponse.thenApply(secondServiceValue -> fisrtServiceValue + secondServiceValue));
+    }
+}

spring-scheduling/src/main/java/com/baeldung/async/FirstAsyncService.java

@@ -0,0 +1,20 @@
+package com.baeldung.async;
+
+import java.util.concurrent.CompletableFuture;
+
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.scheduling.annotation.AsyncResult;
+import org.springframework.stereotype.Service;
+
+@Service
+public class FirstAsyncService {
+
+    @Async
+    public CompletableFuture<String> asyncGetData() throws InterruptedException {
+        System.out.println("Execute method asynchronously " + Thread.currentThread()
+            .getName());
+        Thread.sleep(4000);
+        return new AsyncResult<>(super.getClass().getSimpleName() + " response !!! ").completable();
+    }
+
+}

spring-scheduling/src/main/java/com/baeldung/async/SecondAsyncService.java

@@ -0,0 +1,20 @@
+package com.baeldung.async;
+
+import java.util.concurrent.CompletableFuture;
+
+import org.springframework.scheduling.annotation.Async;
+import org.springframework.scheduling.annotation.AsyncResult;
+import org.springframework.stereotype.Service;
+
+@Service
+public class SecondAsyncService {
+
+    @Async
+    public CompletableFuture<String> asyncGetData() throws InterruptedException {
+        System.out.println("Execute method asynchronously " + Thread.currentThread()
+            .getName());
+        Thread.sleep(4000);
+        return new AsyncResult<>(super.getClass().getSimpleName() + " response !!! ").completable();
+    }
+
+}

spring-scheduling/src/test/java/com/baeldung/async/AsyncServiceUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.async;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+import com.baeldung.async.config.SpringAsyncConfig;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = { SpringAsyncConfig.class }, loader = AnnotationConfigContextLoader.class)
+public class AsyncServiceUnitTest {
+
+    @Autowired
+    private AsyncService asyncServiceExample;
+
+    // tests
+
+    @Test
+    public void testAsyncAnnotationForMergedServicesResponse() throws InterruptedException, ExecutionException {
+        System.out.println("Invoking an asynchronous method. " + Thread.currentThread()
+            .getName());
+        CompletableFuture<String> completableFuture = asyncServiceExample.asyncMergeServicesResponse();
+
+        while (true) {
+            if (completableFuture.isDone()) {
+                System.out.println("Result from asynchronous process - " + completableFuture.get());
+                break;
+            }
+            System.out.println("Continue doing something else. ");
+            Thread.sleep(1000);
+        }
+    }
+
+}