Expose prestartAllCoreThreads on ExecutorService

See gh-1246

spring-context/src/main/java/org/springframework/scheduling/concurrent/ThreadPoolExecutorFactoryBean.java

@@ -73,12 +73,14 @@ public class ThreadPoolExecutorFactoryBean extends ExecutorConfigurationSupport
 
 	private int keepAliveSeconds = 60;
 
-	private boolean allowCoreThreadTimeOut = false;
-
 	private int queueCapacity = Integer.MAX_VALUE;
 
+	private boolean allowCoreThreadTimeOut = false;
+
 	private boolean exposeUnconfigurableExecutor = false;
 
+	private boolean prestartAllCoreThreads = false;
+
 	@Nullable
 	private ExecutorService exposedExecutor;
 
@@ -130,6 +132,17 @@ public void setQueueCapacity(int queueCapacity) {
 		this.queueCapacity = queueCapacity;
 	}
 
+	/**
+	 * Specify whether this FactoryBean should prestart all threads
+	 * for the created executor.
+	 * <p>Default is "false".
+	 * Switch this flag to "true" to prestart the threads allocated for the current executor
+	 * @see java.util.concurrent.ThreadPoolExecutor#prestartAllCoreThreads
+	 */
+	public void setPrestartAllCoreThreads(boolean prestartAllCoreThreads) {
+		this.prestartAllCoreThreads = prestartAllCoreThreads;
+	}
+
 	/**
 	 * Specify whether this FactoryBean should expose an unconfigurable
 	 * decorator for the created executor.
@@ -154,6 +167,10 @@ protected ExecutorService initializeExecutor(
 			executor.allowCoreThreadTimeOut(true);
 		}
 
+		if (this.prestartAllCoreThreads) {
+			executor.prestartAllCoreThreads();
+		}
+
 		// Wrap executor with an unconfigurable decorator.
 		this.exposedExecutor = (this.exposeUnconfigurableExecutor ?
 				Executors.unconfigurableExecutorService(executor) : executor);

spring-context/src/test/java/org/springframework/scheduling/concurrent/ThreadPoolExecutorFactoryBeanTests.java

@@ -16,17 +16,25 @@
 
 package org.springframework.scheduling.concurrent;
 
+import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.FutureTask;
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.context.ApplicationContext;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
 
 /**
  * @author Juergen Hoeller
@@ -44,6 +52,21 @@ void defaultExecutor() throws Exception {
 		context.close();
 	}
 
+	@Test
+	public void executorWithPreStartedThreads() throws Exception {
+		ConfigurableApplicationContext context = new AnnotationConfigApplicationContext(ExecutorConfigWithPreStartedThreads.class);
+		ThreadPoolExecutor executor = context.getBean("childExecutor", ThreadPoolExecutor.class);
+
+		verify(executor).prestartAllCoreThreads();
+	}
+
+	@Test
+	public void executorWithNoPreStartedThreads() throws Exception {
+		ConfigurableApplicationContext context = new AnnotationConfigApplicationContext(ExecutorConfigWithNoPreStartedThreads.class);
+		ThreadPoolExecutor executor = context.getBean("childExecutor", ThreadPoolExecutor.class);
+
+		verify(executor, never()).prestartAllCoreThreads();
+	}
 
 	@Configuration
 	static class ExecutorConfig {
@@ -55,4 +78,45 @@ ThreadPoolExecutorFactoryBean executor() {
 
 	}
 
+	@Configuration
+	public static class ExecutorConfigWithPreStartedThreads {
+
+		@Bean
+		public ThreadPoolExecutorFactoryBean executorChildFactory() {
+			ThreadPoolExecutorFactoryBeanMockingChild threadPoolExecutorFactoryBeanMockingChild = new ThreadPoolExecutorFactoryBeanMockingChild();
+			threadPoolExecutorFactoryBeanMockingChild.setPrestartAllCoreThreads(true);
+			return threadPoolExecutorFactoryBeanMockingChild;
+		}
+
+		@Bean
+		public ExecutorService childExecutor() {
+			return executorChildFactory().getObject();
+		}
+	}
+
+	@Configuration
+	public static class ExecutorConfigWithNoPreStartedThreads {
+
+		@Bean
+		public ThreadPoolExecutorFactoryBean executorChildFactory() {
+			return new ThreadPoolExecutorFactoryBeanMockingChild();
+		}
+
+		@Bean
+		public ExecutorService childExecutor() {
+			return executorChildFactory().getObject();
+		}
+	}
+
+	private static class ThreadPoolExecutorFactoryBeanMockingChild extends ThreadPoolExecutorFactoryBean {
+		@Override
+		protected ThreadPoolExecutor createExecutor(
+				int corePoolSize, int maxPoolSize, int keepAliveSeconds, BlockingQueue<Runnable> queue,
+				ThreadFactory threadFactory, RejectedExecutionHandler rejectedExecutionHandler) {
+
+			return mock(ThreadPoolExecutor.class);
+		}
+	}
+
+
 }