Add concurrency throttle and flexible task callback to SyncTaskExecutor

Closes gh-35460

spring-core/src/test/java/org/springframework/core/task/SyncTaskExecutorTests.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright 2002-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.task;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIOException;
+import static org.assertj.core.api.Assertions.assertThatNoException;
+
+/**
+ * @author Juergen Hoeller
+ * @since 7.0
+ */
+class SyncTaskExecutorTests {
+
+	@Test
+	void plainExecution() {
+		SyncTaskExecutor taskExecutor = new SyncTaskExecutor();
+
+		ConcurrentClass target = new ConcurrentClass();
+		assertThatNoException().isThrownBy(() -> taskExecutor.execute(target::concurrentOperation));
+		assertThat(taskExecutor.execute(target::concurrentOperationWithResult)).isEqualTo("result");
+		assertThatIOException().isThrownBy(() -> taskExecutor.execute(target::concurrentOperationWithException));
+	}
+
+	@Test
+	void withConcurrencyLimit() {
+		SyncTaskExecutor taskExecutor = new SyncTaskExecutor();
+		taskExecutor.setConcurrencyLimit(2);
+
+		ConcurrentClass target = new ConcurrentClass();
+		List<CompletableFuture<?>> futures = new ArrayList<>(10);
+		for (int i = 0; i < 10; i++) {
+			futures.add(CompletableFuture.runAsync(() -> taskExecutor.execute(target::concurrentOperation)));
+		}
+		CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
+		assertThat(target.current).hasValue(0);
+		assertThat(target.counter).hasValue(10);
+	}
+
+	@Test
+	void withConcurrencyLimitAndResult() {
+		SyncTaskExecutor taskExecutor = new SyncTaskExecutor();
+		taskExecutor.setConcurrencyLimit(2);
+
+		ConcurrentClass target = new ConcurrentClass();
+		List<CompletableFuture<?>> futures = new ArrayList<>(10);
+		for (int i = 0; i < 10; i++) {
+			futures.add(CompletableFuture.runAsync(() ->
+					assertThat(taskExecutor.execute(target::concurrentOperationWithResult)).isEqualTo("result")));
+		}
+		CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
+		assertThat(target.current).hasValue(0);
+		assertThat(target.counter).hasValue(10);
+	}
+
+	@Test
+	void withConcurrencyLimitAndException() {
+		SyncTaskExecutor taskExecutor = new SyncTaskExecutor();
+		taskExecutor.setConcurrencyLimit(2);
+
+		ConcurrentClass target = new ConcurrentClass();
+		List<CompletableFuture<?>> futures = new ArrayList<>(10);
+		for (int i = 0; i < 10; i++) {
+			futures.add(CompletableFuture.runAsync(() ->
+					assertThatIOException().isThrownBy(() -> taskExecutor.execute(target::concurrentOperationWithException))));
+		}
+		CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
+		assertThat(target.current).hasValue(0);
+		assertThat(target.counter).hasValue(10);
+	}
+
+
+	static class ConcurrentClass {
+
+		final AtomicInteger current = new AtomicInteger();
+
+		final AtomicInteger counter = new AtomicInteger();
+
+		public void concurrentOperation() {
+			if (current.incrementAndGet() > 2) {
+				throw new IllegalStateException();
+			}
+			try {
+				Thread.sleep(10);
+			}
+			catch (InterruptedException ex) {
+				throw new IllegalStateException(ex);
+			}
+			current.decrementAndGet();
+			counter.incrementAndGet();
+		}
+
+		public String concurrentOperationWithResult() {
+			concurrentOperation();
+			return "result";
+		}
+
+		public String concurrentOperationWithException() throws IOException {
+			concurrentOperation();
+			throw new IOException();
+		}
+	}
+
+}