Merge pull request #45155 from quaff

* pr/45155:
  Polish contribution
  Add support for SimpleTaskExecutor#reject-tasks-when-limit-reached

Closes gh-45155

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskExecutionProperties.java

@@ -77,12 +77,25 @@ public class TaskExecutionProperties {
 
 	public static class Simple {
 
+		/**
+		 * Whether to reject tasks when the concurrency limit has been reached.
+		 */
+		private boolean rejectTasksWhenLimitReached;
+
 		/**
 		 * Set the maximum number of parallel accesses allowed. -1 indicates no
 		 * concurrency limit at all.
 		 */
 		private Integer concurrencyLimit;
 
+		public boolean isRejectTasksWhenLimitReached() {
+			return this.rejectTasksWhenLimitReached;
+		}
+
+		public void setRejectTasksWhenLimitReached(boolean rejectTasksWhenLimitReached) {
+			this.rejectTasksWhenLimitReached = rejectTasksWhenLimitReached;
+		}
+
 		public Integer getConcurrencyLimit() {
 			return this.concurrencyLimit;
 		}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/task/TaskExecutorConfigurations.java

@@ -135,6 +135,7 @@ class TaskExecutorConfigurations {
 			builder = builder.customizers(this.taskExecutorCustomizers.orderedStream()::iterator);
 			builder = builder.taskDecorator(this.taskDecorator.getIfUnique());
 			TaskExecutionProperties.Simple simple = this.properties.getSimple();
+			builder = builder.rejectTasksWhenLimitReached(simple.isRejectTasksWhenLimitReached());
 			builder = builder.concurrencyLimit(simple.getConcurrencyLimit());
 			TaskExecutionProperties.Shutdown shutdown = this.properties.getShutdown();
 			if (shutdown.isAwaitTermination()) {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/task/TaskExecutionAutoConfigurationTests.java

@@ -83,10 +83,12 @@ class TaskExecutionAutoConfigurationTests {
 	void simpleAsyncTaskExecutorBuilderShouldReadProperties() {
 		this.contextRunner
 			.withPropertyValues("spring.task.execution.thread-name-prefix=mytest-",
+					"spring.task.execution.simple.reject-tasks-when-limit-reached=true",
 					"spring.task.execution.simple.concurrency-limit=1",
 					"spring.task.execution.shutdown.await-termination=true",
 					"spring.task.execution.shutdown.await-termination-period=30s")
 			.run(assertSimpleAsyncTaskExecutor((taskExecutor) -> {
+				assertThat(taskExecutor).hasFieldOrPropertyWithValue("rejectTasksWhenLimitReached", true);
 				assertThat(taskExecutor.getConcurrencyLimit()).isEqualTo(1);
 				assertThat(taskExecutor.getThreadNamePrefix()).isEqualTo("mytest-");
 				assertThat(taskExecutor).hasFieldOrPropertyWithValue("taskTerminationTimeout", 30000L);

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/task/SimpleAsyncTaskExecutorBuilder.java

@@ -41,6 +41,7 @@ import org.springframework.util.CollectionUtils;
  * @author Stephane Nicoll
  * @author Filip Hrisafov
  * @author Moritz Halbritter
+ * @author Yanming Zhou
  * @since 3.2.0
  */
 public class SimpleAsyncTaskExecutorBuilder {
@@ -49,6 +50,8 @@ public class SimpleAsyncTaskExecutorBuilder {
 
 	private final String threadNamePrefix;
 
+	private final boolean rejectTasksWhenLimitReached;
+
 	private final Integer concurrencyLimit;
 
 	private final TaskDecorator taskDecorator;
@@ -58,14 +61,15 @@ public class SimpleAsyncTaskExecutorBuilder {
 	private final Duration taskTerminationTimeout;
 
 	public SimpleAsyncTaskExecutorBuilder() {
-		this(null, null, null, null, null, null);
+		this(null, null, false, null, null, null, null);
 	}
 
-	private SimpleAsyncTaskExecutorBuilder(Boolean virtualThreads, String threadNamePrefix, Integer concurrencyLimit,
-			TaskDecorator taskDecorator, Set<SimpleAsyncTaskExecutorCustomizer> customizers,
-			Duration taskTerminationTimeout) {
+	private SimpleAsyncTaskExecutorBuilder(Boolean virtualThreads, String threadNamePrefix,
+			boolean rejectTasksWhenLimitReached, Integer concurrencyLimit, TaskDecorator taskDecorator,
+			Set<SimpleAsyncTaskExecutorCustomizer> customizers, Duration taskTerminationTimeout) {
 		this.virtualThreads = virtualThreads;
 		this.threadNamePrefix = threadNamePrefix;
+		this.rejectTasksWhenLimitReached = rejectTasksWhenLimitReached;
 		this.concurrencyLimit = concurrencyLimit;
 		this.taskDecorator = taskDecorator;
 		this.customizers = customizers;
@@ -78,8 +82,9 @@ public class SimpleAsyncTaskExecutorBuilder {
 	 * @return a new builder instance
 	 */
 	public SimpleAsyncTaskExecutorBuilder threadNamePrefix(String threadNamePrefix) {
-		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, threadNamePrefix, this.concurrencyLimit,
-				this.taskDecorator, this.customizers, this.taskTerminationTimeout);
+		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, threadNamePrefix,
+				this.rejectTasksWhenLimitReached, this.concurrencyLimit, this.taskDecorator, this.customizers,
+				this.taskTerminationTimeout);
 	}
 
 	/**
@@ -88,8 +93,24 @@ public class SimpleAsyncTaskExecutorBuilder {
 	 * @return a new builder instance
 	 */
 	public SimpleAsyncTaskExecutorBuilder virtualThreads(Boolean virtualThreads) {
-		return new SimpleAsyncTaskExecutorBuilder(virtualThreads, this.threadNamePrefix, this.concurrencyLimit,
-				this.taskDecorator, this.customizers, this.taskTerminationTimeout);
+		return new SimpleAsyncTaskExecutorBuilder(virtualThreads, this.threadNamePrefix,
+				this.rejectTasksWhenLimitReached, this.concurrencyLimit, this.taskDecorator, this.customizers,
+				this.taskTerminationTimeout);
+	}
+
+	/**
+	 * Set whether to reject tasks when the concurrency limit has been reached. By default
+	 * {@code false} to block the caller until the submission can be accepted. Switch to
+	 * {@code true} for immediate rejection instead.
+	 * @param rejectTasksWhenLimitReached whether to reject tasks when the concurrency
+	 * limit has been reached
+	 * @return a new builder instance
+	 * @since 3.5.0
+	 */
+	public SimpleAsyncTaskExecutorBuilder rejectTasksWhenLimitReached(boolean rejectTasksWhenLimitReached) {
+		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix,
+				rejectTasksWhenLimitReached, this.concurrencyLimit, this.taskDecorator, this.customizers,
+				this.taskTerminationTimeout);
 	}
 
 	/**
@@ -98,8 +119,9 @@ public class SimpleAsyncTaskExecutorBuilder {
 	 * @return a new builder instance
 	 */
 	public SimpleAsyncTaskExecutorBuilder concurrencyLimit(Integer concurrencyLimit) {
-		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix, concurrencyLimit,
-				this.taskDecorator, this.customizers, this.taskTerminationTimeout);
+		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix,
+				this.rejectTasksWhenLimitReached, concurrencyLimit, this.taskDecorator, this.customizers,
+				this.taskTerminationTimeout);
 	}
 
 	/**
@@ -108,8 +130,9 @@ public class SimpleAsyncTaskExecutorBuilder {
 	 * @return a new builder instance
 	 */
 	public SimpleAsyncTaskExecutorBuilder taskDecorator(TaskDecorator taskDecorator) {
-		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix, this.concurrencyLimit,
-				taskDecorator, this.customizers, this.taskTerminationTimeout);
+		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix,
+				this.rejectTasksWhenLimitReached, this.concurrencyLimit, taskDecorator, this.customizers,
+				this.taskTerminationTimeout);
 	}
 
 	/**
@@ -119,8 +142,9 @@ public class SimpleAsyncTaskExecutorBuilder {
 	 * @since 3.2.1
 	 */
 	public SimpleAsyncTaskExecutorBuilder taskTerminationTimeout(Duration taskTerminationTimeout) {
-		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix, this.concurrencyLimit,
-				this.taskDecorator, this.customizers, taskTerminationTimeout);
+		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix,
+				this.rejectTasksWhenLimitReached, this.concurrencyLimit, this.taskDecorator, this.customizers,
+				taskTerminationTimeout);
 	}
 
 	/**
@@ -149,8 +173,9 @@ public class SimpleAsyncTaskExecutorBuilder {
 	public SimpleAsyncTaskExecutorBuilder customizers(
 			Iterable<? extends SimpleAsyncTaskExecutorCustomizer> customizers) {
 		Assert.notNull(customizers, "'customizers' must not be null");
-		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix, this.concurrencyLimit,
-				this.taskDecorator, append(null, customizers), this.taskTerminationTimeout);
+		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix,
+				this.rejectTasksWhenLimitReached, this.concurrencyLimit, this.taskDecorator, append(null, customizers),
+				this.taskTerminationTimeout);
 	}
 
 	/**
@@ -177,8 +202,9 @@ public class SimpleAsyncTaskExecutorBuilder {
 	public SimpleAsyncTaskExecutorBuilder additionalCustomizers(
 			Iterable<? extends SimpleAsyncTaskExecutorCustomizer> customizers) {
 		Assert.notNull(customizers, "'customizers' must not be null");
-		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix, this.concurrencyLimit,
-				this.taskDecorator, append(this.customizers, customizers), this.taskTerminationTimeout);
+		return new SimpleAsyncTaskExecutorBuilder(this.virtualThreads, this.threadNamePrefix,
+				this.rejectTasksWhenLimitReached, this.concurrencyLimit, this.taskDecorator,
+				append(this.customizers, customizers), this.taskTerminationTimeout);
 	}
 
 	/**
@@ -217,6 +243,7 @@ public class SimpleAsyncTaskExecutorBuilder {
 		PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
 		map.from(this.virtualThreads).to(taskExecutor::setVirtualThreads);
 		map.from(this.threadNamePrefix).whenHasText().to(taskExecutor::setThreadNamePrefix);
+		map.from(this.rejectTasksWhenLimitReached).to(taskExecutor::setRejectTasksWhenLimitReached);
 		map.from(this.concurrencyLimit).to(taskExecutor::setConcurrencyLimit);
 		map.from(this.taskDecorator).to(taskExecutor::setTaskDecorator);
 		map.from(this.taskTerminationTimeout).as(Duration::toMillis).to(taskExecutor::setTaskTerminationTimeout);

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/task/SimpleAsyncTaskExecutorBuilderTests.java

@@ -40,6 +40,7 @@ import static org.mockito.Mockito.spy;
  * @author Stephane Nicoll
  * @author Filip Hrisafov
  * @author Moritz Halbritter
+ * @author Yanming Zhou
  */
 class SimpleAsyncTaskExecutorBuilderTests {
 
@@ -58,6 +59,12 @@ class SimpleAsyncTaskExecutorBuilderTests {
 		SimpleAsyncTaskExecutorAssert.assertThat(executor).usesVirtualThreads();
 	}
 
+	@Test
+	void rejectTasksWhenLimitReachedShouldApply() {
+		SimpleAsyncTaskExecutor executor = this.builder.rejectTasksWhenLimitReached(true).build();
+		assertThat(executor).extracting("rejectTasksWhenLimitReached").isEqualTo(true);
+	}
+
 	@Test
 	void concurrencyLimitShouldApply() {
 		SimpleAsyncTaskExecutor executor = this.builder.concurrencyLimit(1).build();