Add auto-configuration support for TaskScheduler

This commit adds support for providing a default ThreadPoolTaskScheduler
with sensible defaults. A new TaskSchedulerBuilder is provided with
defaults from the `spring.task.scheduler.*` namespace and can be used
to create custom instances.

If no custom `TaskScheduler` bean is present, `@EnableScheduling` now
uses the auto-configured task scheduler.

Closes gh-1397

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

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.boot.autoconfigure.task;
+
+import java.util.stream.Collectors;
+
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.boot.task.TaskSchedulerBuilder;
+import org.springframework.boot.task.TaskSchedulerCustomizer;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.scheduling.TaskScheduler;
+import org.springframework.scheduling.annotation.SchedulingConfigurer;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
+import org.springframework.scheduling.config.TaskManagementConfigUtils;
+
+/**
+ * {@link EnableAutoConfiguration Auto-configuration} for {@link TaskScheduler}.
+ *
+ * @author Stephane Nicoll
+ * @since 2.1.0
+ */
+@ConditionalOnClass(ThreadPoolTaskScheduler.class)
+@Configuration
+@EnableConfigurationProperties(TaskSchedulingProperties.class)
+public class TaskSchedulingAutoConfiguration {
+
+	@Bean
+	@ConditionalOnBean(name = TaskManagementConfigUtils.SCHEDULED_ANNOTATION_PROCESSOR_BEAN_NAME)
+	@ConditionalOnMissingBean({ SchedulingConfigurer.class, TaskScheduler.class })
+	public ThreadPoolTaskScheduler taskScheduler(TaskSchedulerBuilder builder) {
+		return builder.build();
+	}
+
+	@Bean
+	@ConditionalOnMissingBean
+	public TaskSchedulerBuilder taskSchedulerBuilder(TaskSchedulingProperties properties,
+			ObjectProvider<TaskSchedulerCustomizer> taskSchedulerCustomizers) {
+		return new TaskSchedulerBuilder().poolSize(properties.getPool().getSize())
+				.threadNamePrefix(properties.getThreadNamePrefix()).customizers(
+						taskSchedulerCustomizers.stream().collect(Collectors.toList()));
+	}
+
+}

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

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.boot.autoconfigure.task;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+/**
+ * Configuration properties for task scheduling.
+ *
+ * @author Stephane Nicoll
+ */
+@ConfigurationProperties("spring.task.scheduling")
+public class TaskSchedulingProperties {
+
+	private final Pool pool = new Pool();
+
+	/**
+	 * Prefix to use for the names of newly created threads.
+	 */
+	private String threadNamePrefix = "scheduling-";
+
+	public Pool getPool() {
+		return this.pool;
+	}
+
+	public String getThreadNamePrefix() {
+		return this.threadNamePrefix;
+	}
+
+	public void setThreadNamePrefix(String threadNamePrefix) {
+		this.threadNamePrefix = threadNamePrefix;
+	}
+
+	public static class Pool {
+
+		/**
+		 * Maximum allowed number of threads.
+		 */
+		private int size = 1;
+
+		public int getSize() {
+			return this.size;
+		}
+
+		public void setSize(int size) {
+			this.size = size;
+		}
+
+	}
+
+}

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

@@ -15,6 +15,6 @@
  */
 
 /**
- * Auto-configuration for task execution.
+ * Auto-configuration for task execution and scheduling.
  */
 package org.springframework.boot.autoconfigure.task;

spring-boot-project/spring-boot-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -96,6 +96,7 @@ org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
 org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
 org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,\
 org.springframework.boot.autoconfigure.reactor.core.ReactorCoreAutoConfiguration,\
+org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration,\
 org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration,\
 org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration,\
 org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration,\
@@ -108,7 +109,7 @@ org.springframework.boot.autoconfigure.security.oauth2.client.reactive.ReactiveO
 org.springframework.boot.autoconfigure.security.oauth2.resource.servlet.OAuth2ResourceServerAutoConfiguration,\
 org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerAutoConfiguration,\
 org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\
-org.springframework.boot.autoconfigure.task.TaskExecutorAutoConfiguration,\
+org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration,\
 org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\
 org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\
 org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\

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

@@ -0,0 +1,180 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.boot.autoconfigure.task;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.Test;
+
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.task.TaskSchedulerCustomizer;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.task.TaskExecutor;
+import org.springframework.scheduling.TaskScheduler;
+import org.springframework.scheduling.annotation.EnableScheduling;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.scheduling.annotation.SchedulingConfigurer;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
+import org.springframework.scheduling.config.ScheduledTaskRegistrar;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link TaskSchedulingAutoConfiguration}.
+ *
+ * @author Stephane Nicoll
+ */
+public class TaskSchedulingAutoConfigurationTests {
+
+	private ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+			.withUserConfiguration(TestConfiguration.class).withConfiguration(
+					AutoConfigurations.of(TaskSchedulingAutoConfiguration.class));
+
+	@Test
+	public void noSchedulingDoesNotExposeTaskScheduler() {
+		this.contextRunner.run(
+				(context) -> assertThat(context).doesNotHaveBean(TaskScheduler.class));
+	}
+
+	@Test
+	public void enableSchedulingWithNoTakExecutorAutoConfiguresOne() {
+		this.contextRunner
+				.withPropertyValues(
+						"spring.task.scheduling.thread-name-prefix=scheduling-test-")
+				.withUserConfiguration(SchedulingConfiguration.class).run((context) -> {
+					assertThat(context).hasSingleBean(TaskExecutor.class);
+					TestBean bean = context.getBean(TestBean.class);
+					Thread.sleep(15);
+					assertThat(bean.threadNames)
+							.allMatch((name) -> name.contains("scheduling-test-"));
+				});
+	}
+
+	@Test
+	public void enableSchedulingWithNoTakExecutorAppliesCustomizers() {
+		this.contextRunner
+				.withPropertyValues(
+						"spring.task.scheduling.thread-name-prefix=scheduling-test-")
+				.withUserConfiguration(SchedulingConfiguration.class,
+						TaskSchedulerCustomizerConfiguration.class)
+				.run((context) -> {
+					assertThat(context).hasSingleBean(TaskExecutor.class);
+					TestBean bean = context.getBean(TestBean.class);
+					Thread.sleep(15);
+					assertThat(bean.threadNames)
+							.allMatch((name) -> name.contains("customized-scheduler-"));
+				});
+	}
+
+	@Test
+	public void enableSchedulingWithExistingTakSchedulerBacksOff() {
+		this.contextRunner.withUserConfiguration(SchedulingConfiguration.class,
+				TaskSchedulerConfiguration.class).run((context) -> {
+					assertThat(context).hasSingleBean(TaskScheduler.class);
+					assertThat(context.getBean(TaskScheduler.class))
+							.isInstanceOf(TestTaskScheduler.class);
+					TestBean bean = context.getBean(TestBean.class);
+					Thread.sleep(15);
+					assertThat(bean.threadNames).containsExactly("test-1");
+				});
+	}
+
+	@Test
+	public void enableSchedulingWithConfigurerBacksOff() {
+		this.contextRunner.withUserConfiguration(SchedulingConfiguration.class,
+				SchedulingConfigurerConfiguration.class).run((context) -> {
+					assertThat(context).doesNotHaveBean(TaskScheduler.class);
+					TestBean bean = context.getBean(TestBean.class);
+					Thread.sleep(15);
+					assertThat(bean.threadNames).containsExactly("test-1");
+				});
+	}
+
+	@Configuration
+	@EnableScheduling
+	static class SchedulingConfiguration {
+
+	}
+
+	@Configuration
+	static class TaskSchedulerConfiguration {
+
+		@Bean
+		public TaskScheduler customTaskScheduler() {
+			return new TestTaskScheduler();
+		}
+
+	}
+
+	@Configuration
+	static class TaskSchedulerCustomizerConfiguration {
+
+		@Bean
+		public TaskSchedulerCustomizer testTaskSchedulerCustomizer() {
+			return ((taskScheduler) -> taskScheduler
+					.setThreadNamePrefix("customized-scheduler-"));
+		}
+
+	}
+
+	@Configuration
+	static class SchedulingConfigurerConfiguration implements SchedulingConfigurer {
+
+		private final TaskScheduler taskScheduler = new TestTaskScheduler();
+
+		@Override
+		public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
+			taskRegistrar.setScheduler(this.taskScheduler);
+		}
+
+	}
+
+	@Configuration
+	static class TestConfiguration {
+
+		@Bean
+		public TestBean testBean() {
+			return new TestBean();
+		}
+
+	}
+
+	static class TestBean {
+
+		private final Set<String> threadNames = new HashSet<>();
+
+		@Scheduled(fixedRate = 10)
+		public void accumulate() {
+			this.threadNames.add(Thread.currentThread().getName());
+		}
+
+	}
+
+	static class TestTaskScheduler extends ThreadPoolTaskScheduler {
+
+		TestTaskScheduler() {
+			setPoolSize(1);
+			setThreadNamePrefix("test-");
+			afterPropertiesSet();
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -169,6 +169,10 @@ content into your application. Rather, pick only the properties that you need.
 	spring.task.execution.pool.queue-capacity= # Queue capacity. An unbounded capacity does not increase the pool and therefore ignores the "max-size" property.
 	spring.task.execution.thread-name-prefix=task- # Prefix to use for the names of newly created threads.
 
+	# TASK SCHEDULING  ({sc-spring-boot-autoconfigure}/task/TaskSchedulingProperties.{sc-ext}[TaskSchedulingProperties])
+	spring.task.scheduling.pool.size=1 # Maximum allowed number of threads.
+	spring.task.scheduling.thread-name-prefix=scheduling- # Prefix to use for the names of newly created threads.
+
 	# ----------------------------------------
 	# WEB PROPERTIES
 	# ----------------------------------------

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -6138,8 +6138,8 @@ in a similar manner, as shown in the following example:
 
 
 
-[[boot-features-task-execution]]
-== Task Execution
+[[boot-features-task-execution-scheduling]]
+== Task Execution and Scheduling
 In the absence of a `TaskExecutor` bean in the context, Spring Boot auto-configures a
 `ThreadPoolTaskExecutor` with sensible defaults that can be automatically associated to
 asynchronous task execution (`@EnableAsync`) and Spring MVC asynchronous request
@@ -6161,6 +6161,12 @@ tasks), the thread pool increases to maximum 16 threads. Shrinking of the pool i
 aggressive as threads are reclaimed when they are idle for 10 seconds (rather than
 60 seconds by default).
 
+A `ThreadPoolTaskScheduler` can also be auto-configured if need to be to be associated to
+scheduled task execution (`@EnableScheduling`). The thread pool uses one thread by default
+and those settings can be fine-tuned using the `spring.task.scheduling` namespace.
+
+Both a `TaskExecutorBuilder` and `TaskSchedulerBuilder` bean are made available in the
+context if a custom executor or scheduler needs to be created.
 
 
 

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

@@ -0,0 +1,187 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.boot.task;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+import org.springframework.boot.context.properties.PropertyMapper;
+import org.springframework.scheduling.TaskScheduler;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+
+/**
+ * Builder that can be used to configure and create a {@link TaskScheduler}. Provides
+ * convenience methods to set common {@link ThreadPoolTaskScheduler} settings. For
+ * advanced configuration, consider using {@link TaskSchedulerCustomizer}.
+ * <p>
+ * In a typical auto-configured Spring Boot application this builder is available as a
+ * bean and can be injected whenever a {@link TaskScheduler} is needed.
+ *
+ * @author Stephane Nicoll
+ * @since 2.1.0
+ */
+public class TaskSchedulerBuilder {
+
+	private final Integer poolSize;
+
+	private final String threadNamePrefix;
+
+	private final Set<TaskSchedulerCustomizer> taskSchedulerCustomizers;
+
+	public TaskSchedulerBuilder(TaskSchedulerCustomizer... taskSchedulerCustomizers) {
+		Assert.notNull(taskSchedulerCustomizers,
+				"TaskSchedulerCustomizers must not be null");
+		this.poolSize = null;
+		this.threadNamePrefix = null;
+		this.taskSchedulerCustomizers = Collections.unmodifiableSet(
+				new LinkedHashSet<>(Arrays.asList(taskSchedulerCustomizers)));
+	}
+
+	public TaskSchedulerBuilder(Integer poolSize, String threadNamePrefix,
+			Set<TaskSchedulerCustomizer> taskSchedulerCustomizers) {
+		this.poolSize = poolSize;
+		this.threadNamePrefix = threadNamePrefix;
+		this.taskSchedulerCustomizers = taskSchedulerCustomizers;
+	}
+
+	/**
+	 * Set the maximum allowed number of threads.
+	 * @param poolSize the pool size to set
+	 * @return a new builder instance
+	 */
+	public TaskSchedulerBuilder poolSize(int poolSize) {
+		return new TaskSchedulerBuilder(poolSize, this.threadNamePrefix,
+				this.taskSchedulerCustomizers);
+	}
+
+	/**
+	 * Set the prefix to use for the names of newly created threads.
+	 * @param threadNamePrefix the thread name prefix to set
+	 * @return a new builder instance
+	 */
+	public TaskSchedulerBuilder threadNamePrefix(String threadNamePrefix) {
+		return new TaskSchedulerBuilder(this.poolSize, threadNamePrefix,
+				this.taskSchedulerCustomizers);
+	}
+
+	/**
+	 * Set the {@link TaskSchedulerCustomizer TaskSchedulerCustomizers} that should be
+	 * applied to the {@link ThreadPoolTaskScheduler}. Customizers are applied in the
+	 * order that they were added after builder configuration has been applied. Setting
+	 * this value will replace any previously configured customizers.
+	 * @param taskSchedulerCustomizers the customizers to set
+	 * @return a new builder instance
+	 * @see #additionalCustomizers(TaskSchedulerCustomizer...)
+	 */
+	public TaskSchedulerBuilder customizers(
+			TaskSchedulerCustomizer... taskSchedulerCustomizers) {
+		Assert.notNull(taskSchedulerCustomizers,
+				"TaskSchedulerCustomizers must not be null");
+		return customizers(Arrays.asList(taskSchedulerCustomizers));
+	}
+
+	/**
+	 * Set the {@link TaskSchedulerCustomizer taskSchedulerCustomizers} that should be
+	 * applied to the {@link ThreadPoolTaskScheduler}. Customizers are applied in the
+	 * order that they were added after builder configuration has been applied. Setting
+	 * this value will replace any previously configured customizers.
+	 * @param taskSchedulerCustomizers the customizers to set
+	 * @return a new builder instance
+	 * @see #additionalCustomizers(TaskSchedulerCustomizer...)
+	 */
+	public TaskSchedulerBuilder customizers(
+			Collection<? extends TaskSchedulerCustomizer> taskSchedulerCustomizers) {
+		Assert.notNull(taskSchedulerCustomizers,
+				"TaskSchedulerCustomizers must not be null");
+		return new TaskSchedulerBuilder(this.poolSize, this.threadNamePrefix,
+				Collections.unmodifiableSet(new LinkedHashSet<TaskSchedulerCustomizer>(
+						taskSchedulerCustomizers)));
+	}
+
+	/**
+	 * Add {@link TaskSchedulerCustomizer taskSchedulerCustomizers} that should be applied
+	 * to the {@link ThreadPoolTaskScheduler}. Customizers are applied in the order that
+	 * they were added after builder configuration has been applied.
+	 * @param taskSchedulerCustomizers the customizers to add
+	 * @return a new builder instance
+	 * @see #customizers(TaskSchedulerCustomizer...)
+	 */
+	public TaskSchedulerBuilder additionalCustomizers(
+			TaskSchedulerCustomizer... taskSchedulerCustomizers) {
+		Assert.notNull(taskSchedulerCustomizers,
+				"TaskSchedulerCustomizers must not be null");
+		return additionalCustomizers(Arrays.asList(taskSchedulerCustomizers));
+	}
+
+	/**
+	 * Add {@link TaskSchedulerCustomizer taskSchedulerCustomizers} that should be applied
+	 * to the {@link ThreadPoolTaskScheduler}. Customizers are applied in the order that
+	 * they were added after builder configuration has been applied.
+	 * @param taskSchedulerCustomizers the customizers to add
+	 * @return a new builder instance
+	 * @see #customizers(TaskSchedulerCustomizer...)
+	 */
+	public TaskSchedulerBuilder additionalCustomizers(
+			Collection<? extends TaskSchedulerCustomizer> taskSchedulerCustomizers) {
+		Assert.notNull(taskSchedulerCustomizers,
+				"TaskSchedulerCustomizers must not be null");
+		return new TaskSchedulerBuilder(this.poolSize, this.threadNamePrefix,
+				append(this.taskSchedulerCustomizers, taskSchedulerCustomizers));
+	}
+
+	/**
+	 * Build a new {@link ThreadPoolTaskScheduler} instance and configure it using this
+	 * builder.
+	 * @return a configured {@link ThreadPoolTaskScheduler} instance.
+	 * @see #configure(ThreadPoolTaskScheduler)
+	 */
+	public ThreadPoolTaskScheduler build() {
+		return configure(new ThreadPoolTaskScheduler());
+	}
+
+	/**
+	 * Configure the provided {@link ThreadPoolTaskScheduler} instance using this builder.
+	 * @param <T> the type of task scheduler
+	 * @param taskScheduler the {@link ThreadPoolTaskScheduler} to configure
+	 * @return the task scheduler instance
+	 * @see #build()
+	 */
+	public <T extends ThreadPoolTaskScheduler> T configure(T taskScheduler) {
+		PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
+		map.from(() -> this.poolSize).to(taskScheduler::setPoolSize);
+		map.from(() -> this.threadNamePrefix).to(taskScheduler::setThreadNamePrefix);
+
+		if (!CollectionUtils.isEmpty(this.taskSchedulerCustomizers)) {
+			for (TaskSchedulerCustomizer customizer : this.taskSchedulerCustomizers) {
+				customizer.customize(taskScheduler);
+			}
+		}
+		return taskScheduler;
+	}
+
+	private static <T> Set<T> append(Set<T> set, Collection<? extends T> additions) {
+		Set<T> result = new LinkedHashSet<>((set != null) ? set : Collections.emptySet());
+		result.addAll(additions);
+		return Collections.unmodifiableSet(result);
+	}
+
+}

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

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.boot.task;
+
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
+
+/**
+ * Callback interface that can be used to customize a {@link ThreadPoolTaskScheduler}.
+ *
+ * @author Stephane Nicoll
+ * @since 2.1.0
+ */
+@FunctionalInterface
+public interface TaskSchedulerCustomizer {
+
+	/**
+	 * Callback to customize a {@link ThreadPoolTaskScheduler} instance.
+	 * @param taskScheduler the task scheduler to customize
+	 */
+	void customize(ThreadPoolTaskScheduler taskScheduler);
+
+}

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

@@ -15,8 +15,6 @@
  */
 
 /**
- * Task execution utilities.
- *
- * @author Stephane Nicoll
+ * Utilities and classes related to task execution and scheduling.
  */
 package org.springframework.boot.task;

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

@@ -0,0 +1,128 @@
+/*
+ * Copyright 2012-2018 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
+ *
+ *      http://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.boot.task;
+
+import java.util.Collections;
+import java.util.Set;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.mockito.Mockito;
+
+import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link TaskSchedulerBuilder}.
+ *
+ * @author Stephane Nicoll
+ */
+public class TaskSchedulerBuilderTests {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	private TaskSchedulerBuilder builder = new TaskSchedulerBuilder();
+
+	@Test
+	public void createWhenCustomizersAreNullShouldThrowException() {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		new TaskSchedulerBuilder((TaskSchedulerCustomizer[]) null);
+	}
+
+	@Test
+	public void poolSettingsShouldApply() {
+		ThreadPoolTaskScheduler scheduler = this.builder.poolSize(4).build();
+		assertThat(scheduler.getPoolSize()).isEqualTo(4);
+	}
+
+	@Test
+	public void threadNamePrefixShouldApply() {
+		ThreadPoolTaskScheduler executor = this.builder.threadNamePrefix("test-").build();
+		assertThat(executor.getThreadNamePrefix()).isEqualTo("test-");
+	}
+
+	@Test
+	public void customizersWhenCustomizersAreNullShouldThrowException() {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		this.builder.customizers((TaskSchedulerCustomizer[]) null);
+	}
+
+	@Test
+	public void customizersCollectionWhenCustomizersAreNullShouldThrowException() {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		this.builder.customizers((Set<TaskSchedulerCustomizer>) null);
+	}
+
+	@Test
+	public void customizersShouldApply() {
+		TaskSchedulerCustomizer customizer = Mockito.mock(TaskSchedulerCustomizer.class);
+		ThreadPoolTaskScheduler executor = this.builder.customizers(customizer).build();
+		Mockito.verify(customizer).customize(executor);
+	}
+
+	@Test
+	public void customizersShouldBeAppliedLast() {
+		ThreadPoolTaskScheduler scheduler = Mockito.spy(new ThreadPoolTaskScheduler());
+		this.builder.poolSize(4).threadNamePrefix("test-")
+				.additionalCustomizers((taskScheduler) -> {
+					Mockito.verify(taskScheduler).setPoolSize(4);
+					Mockito.verify(taskScheduler).setThreadNamePrefix("test-");
+				});
+		this.builder.configure(scheduler);
+	}
+
+	@Test
+	public void customizersShouldReplaceExisting() {
+		TaskSchedulerCustomizer customizer1 = Mockito.mock(TaskSchedulerCustomizer.class);
+		TaskSchedulerCustomizer customizer2 = Mockito.mock(TaskSchedulerCustomizer.class);
+		ThreadPoolTaskScheduler executor = this.builder.customizers(customizer1)
+				.customizers(Collections.singleton(customizer2)).build();
+		Mockito.verifyZeroInteractions(customizer1);
+		Mockito.verify(customizer2).customize(executor);
+	}
+
+	@Test
+	public void additionalCustomizersWhenCustomizersAreNullShouldThrowException() {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		this.builder.additionalCustomizers((TaskSchedulerCustomizer[]) null);
+	}
+
+	@Test
+	public void additionalCustomizersCollectionWhenCustomizersAreNullShouldThrowException() {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("TaskSchedulerCustomizers must not be null");
+		this.builder.additionalCustomizers((Set<TaskSchedulerCustomizer>) null);
+	}
+
+	@Test
+	public void additionalCustomizersShouldAddToExisting() {
+		TaskSchedulerCustomizer customizer1 = Mockito.mock(TaskSchedulerCustomizer.class);
+		TaskSchedulerCustomizer customizer2 = Mockito.mock(TaskSchedulerCustomizer.class);
+		ThreadPoolTaskScheduler scheduler = this.builder.customizers(customizer1)
+				.additionalCustomizers(customizer2).build();
+		Mockito.verify(customizer1).customize(scheduler);
+		Mockito.verify(customizer2).customize(scheduler);
+	}
+
+}