Allow customization of Spring Batch TaskExecutor

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/batch/BasicBatchConfigurer.java

@@ -29,6 +29,7 @@
 import org.springframework.boot.autoconfigure.batch.BatchProperties.Isolation;
 import org.springframework.boot.autoconfigure.transaction.TransactionManagerCustomizers;
 import org.springframework.boot.context.properties.PropertyMapper;
+import org.springframework.core.task.TaskExecutor;
 import org.springframework.jdbc.datasource.DataSourceTransactionManager;
 import org.springframework.transaction.PlatformTransactionManager;
 
@@ -39,6 +40,7 @@
  * @author Andy Wilkinson
  * @author Kazuki Shimizu
  * @author Stephane Nicoll
+ * @author Andreas Ahlenstorf
  * @since 1.0.0
  */
 public class BasicBatchConfigurer implements BatchConfigurer, InitializingBean {
@@ -51,6 +53,8 @@ public class BasicBatchConfigurer implements BatchConfigurer, InitializingBean {
 
 	private final TransactionManagerCustomizers transactionManagerCustomizers;
 
+	private final TaskExecutor taskExecutor;
+
 	private JobRepository jobRepository;
 
 	private JobLauncher jobLauncher;
@@ -63,12 +67,30 @@ public class BasicBatchConfigurer implements BatchConfigurer, InitializingBean {
 	 * @param dataSource the underlying data source
 	 * @param transactionManagerCustomizers transaction manager customizers (or
 	 * {@code null})
+	 * @deprecated since 2.7.0 for removal in 3.0.0 in favor of
+	 * {@link #BasicBatchConfigurer(BatchProperties, DataSource, TransactionManagerCustomizers, TaskExecutor)}
 	 */
+	@Deprecated
 	protected BasicBatchConfigurer(BatchProperties properties, DataSource dataSource,
 			TransactionManagerCustomizers transactionManagerCustomizers) {
+		this(properties, dataSource, transactionManagerCustomizers, null);
+	}
+
+	/**
+	 * Create a new {@link BasicBatchConfigurer} instance.
+	 * @param properties the batch properties
+	 * @param dataSource the underlying data source
+	 * @param transactionManagerCustomizers transaction manager customizers (or
+	 * {@code null})
+	 * @param taskExecutor the executor to be used by {@link JobLauncher} (or
+	 * {@code null})
+	 */
+	protected BasicBatchConfigurer(BatchProperties properties, DataSource dataSource,
+			TransactionManagerCustomizers transactionManagerCustomizers, TaskExecutor taskExecutor) {
 		this.properties = properties;
 		this.dataSource = dataSource;
 		this.transactionManagerCustomizers = transactionManagerCustomizers;
+		this.taskExecutor = taskExecutor;
 	}
 
 	@Override
@@ -120,6 +142,9 @@ protected JobExplorer createJobExplorer() throws Exception {
 	protected JobLauncher createJobLauncher() throws Exception {
 		SimpleJobLauncher jobLauncher = new SimpleJobLauncher();
 		jobLauncher.setJobRepository(getJobRepository());
+		if (this.taskExecutor != null) {
+			jobLauncher.setTaskExecutor(this.taskExecutor);
+		}
 		jobLauncher.afterPropertiesSet();
 		return jobLauncher;
 	}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/batch/BatchConfigurerConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -27,12 +27,14 @@
 import org.springframework.boot.autoconfigure.transaction.TransactionManagerCustomizers;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.task.TaskExecutor;
 import org.springframework.transaction.PlatformTransactionManager;
 
 /**
  * Provide a {@link BatchConfigurer} according to the current environment.
  *
  * @author Stephane Nicoll
+ * @author Andreas Ahlenstorf
  */
 @ConditionalOnClass(PlatformTransactionManager.class)
 @ConditionalOnBean(DataSource.class)
@@ -47,9 +49,10 @@ static class JdbcBatchConfiguration {
 		@Bean
 		BasicBatchConfigurer batchConfigurer(BatchProperties properties, DataSource dataSource,
 				@BatchDataSource ObjectProvider<DataSource> batchDataSource,
-				ObjectProvider<TransactionManagerCustomizers> transactionManagerCustomizers) {
+				ObjectProvider<TransactionManagerCustomizers> transactionManagerCustomizers,
+				@BatchTaskExecutor ObjectProvider<TaskExecutor> batchTaskExecutor) {
 			return new BasicBatchConfigurer(properties, batchDataSource.getIfAvailable(() -> dataSource),
-					transactionManagerCustomizers.getIfAvailable());
+					transactionManagerCustomizers.getIfAvailable(), batchTaskExecutor.getIfAvailable());
 		}
 
 	}
@@ -63,9 +66,11 @@ static class JpaBatchConfiguration {
 		JpaBatchConfigurer batchConfigurer(BatchProperties properties, DataSource dataSource,
 				@BatchDataSource ObjectProvider<DataSource> batchDataSource,
 				ObjectProvider<TransactionManagerCustomizers> transactionManagerCustomizers,
-				EntityManagerFactory entityManagerFactory) {
+				EntityManagerFactory entityManagerFactory,
+				@BatchTaskExecutor ObjectProvider<TaskExecutor> batchTaskExecutor) {
 			return new JpaBatchConfigurer(properties, batchDataSource.getIfAvailable(() -> dataSource),
-					transactionManagerCustomizers.getIfAvailable(), entityManagerFactory);
+					transactionManagerCustomizers.getIfAvailable(), entityManagerFactory,
+					batchTaskExecutor.getIfAvailable());
 		}
 
 	}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/batch/BatchTaskExecutor.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2012-2022 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.boot.autoconfigure.batch;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.beans.factory.annotation.Qualifier;
+
+/**
+ * Qualifier annotation for a TaskExecutor to be injected into Batch auto-configuration.
+ *
+ * @author Andreas Ahlenstorf
+ * @since 2.7.0
+ */
+@Target({ ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.TYPE, ElementType.ANNOTATION_TYPE })
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Qualifier
+public @interface BatchTaskExecutor {
+
+}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/batch/JpaBatchConfigurer.java

@@ -24,13 +24,15 @@
 
 import org.springframework.boot.autoconfigure.batch.BatchProperties.Isolation;
 import org.springframework.boot.autoconfigure.transaction.TransactionManagerCustomizers;
+import org.springframework.core.task.TaskExecutor;
 import org.springframework.orm.jpa.JpaTransactionManager;
 import org.springframework.transaction.PlatformTransactionManager;
 
 /**
  * A {@link BasicBatchConfigurer} tailored for JPA.
  *
  * @author Stephane Nicoll
+ * @author Andreas Ahlenstorf
  * @since 2.0.0
  */
 public class JpaBatchConfigurer extends BasicBatchConfigurer {
@@ -46,10 +48,30 @@ public class JpaBatchConfigurer extends BasicBatchConfigurer {
 	 * @param transactionManagerCustomizers transaction manager customizers (or
 	 * {@code null})
 	 * @param entityManagerFactory the entity manager factory (or {@code null})
+	 * @deprecated since 2.7.0 for removal in 3.0.0 in favor of
+	 * {@link #JpaBatchConfigurer(BatchProperties, DataSource, TransactionManagerCustomizers, EntityManagerFactory, TaskExecutor)}
 	 */
+	@Deprecated
 	protected JpaBatchConfigurer(BatchProperties properties, DataSource dataSource,
 			TransactionManagerCustomizers transactionManagerCustomizers, EntityManagerFactory entityManagerFactory) {
-		super(properties, dataSource, transactionManagerCustomizers);
+		super(properties, dataSource, transactionManagerCustomizers, null);
+		this.entityManagerFactory = entityManagerFactory;
+	}
+
+	/**
+	 * Create a new {@link BasicBatchConfigurer} instance.
+	 * @param properties the batch properties
+	 * @param dataSource the underlying data source
+	 * @param transactionManagerCustomizers transaction manager customizers (or
+	 * {@code null})
+	 * @param entityManagerFactory the entity manager factory (or {@code null})
+	 * @param taskExecutor the executor to be used by
+	 * {@link org.springframework.batch.core.launch.JobLauncher} (or {@code null})
+	 */
+	protected JpaBatchConfigurer(BatchProperties properties, DataSource dataSource,
+			TransactionManagerCustomizers transactionManagerCustomizers, EntityManagerFactory entityManagerFactory,
+			TaskExecutor taskExecutor) {
+		super(properties, dataSource, transactionManagerCustomizers, taskExecutor);
 		this.entityManagerFactory = entityManagerFactory;
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/batch/BatchAutoConfigurationTests.java

@@ -63,6 +63,8 @@
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Primary;
+import org.springframework.core.task.SyncTaskExecutor;
+import org.springframework.core.task.TaskExecutor;
 import org.springframework.jdbc.BadSqlGrammarException;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.jdbc.datasource.DataSourceTransactionManager;
@@ -80,6 +82,7 @@
  * @author Stephane Nicoll
  * @author Vedran Pavic
  * @author Kazuki Shimizu
+ * @author Andreas Ahlenstorf
  */
 @ExtendWith(OutputCaptureExtension.class)
 class BatchAutoConfigurationTests {
@@ -367,6 +370,37 @@ void whenTheUserDefinesTheirOwnDatabaseInitializerThenTheAutoConfiguredBatchInit
 						.hasBean("customInitializer"));
 	}
 
+	@Test
+	void jobLauncherUsesBatchTaskExecutorIfPresent() {
+		this.contextRunner.withUserConfiguration(TestConfiguration.class, EmbeddedDataSourceConfiguration.class,
+				BatchTaskExecutorConfiguration.class).run((context) -> {
+					assertThat(context).hasBean("batchTaskExecutor");
+
+					TaskExecutor taskExecutor = context.getBean("batchTaskExecutor", TaskExecutor.class);
+					BatchConfigurer batchConfigurer = context.getBean(BatchConfigurer.class);
+
+					assertThat(batchConfigurer.getJobLauncher()).hasFieldOrPropertyWithValue("taskExecutor",
+							taskExecutor);
+				});
+	}
+
+	@Test
+	void jobLauncherConfiguredByJpaBatchConfigurerUsesBatchTaskExecutorIfPresent() {
+		this.contextRunner.withUserConfiguration(TestConfiguration.class, EmbeddedDataSourceConfiguration.class,
+				HibernateJpaAutoConfiguration.class, BatchTaskExecutorConfiguration.class).run((context) -> {
+					PlatformTransactionManager transactionManager = context.getBean(PlatformTransactionManager.class);
+					assertThat(transactionManager.toString().contains("JpaTransactionManager")).isTrue();
+
+					assertThat(context).hasBean("batchTaskExecutor");
+
+					TaskExecutor taskExecutor = context.getBean("batchTaskExecutor", TaskExecutor.class);
+					BatchConfigurer batchConfigurer = context.getBean(BatchConfigurer.class);
+
+					assertThat(batchConfigurer.getJobLauncher()).hasFieldOrPropertyWithValue("taskExecutor",
+							taskExecutor);
+				});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	protected static class BatchDataSourceConfiguration {
 
@@ -531,4 +565,15 @@ DataSourceScriptDatabaseInitializer customInitializer(DataSource dataSource) {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	protected static class BatchTaskExecutorConfiguration {
+
+		@BatchTaskExecutor
+		@Bean
+		public TaskExecutor batchTaskExecutor() {
+			return new SyncTaskExecutor();
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/batch/JobLauncherApplicationRunnerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -223,7 +223,7 @@ static class BatchConfiguration extends BasicBatchConfigurer {
 		private final DataSource dataSource;
 
 		protected BatchConfiguration(DataSource dataSource) {
-			super(new BatchProperties(), dataSource, new TransactionManagerCustomizers(null));
+			super(new BatchProperties(), dataSource, new TransactionManagerCustomizers(null), null);
 			this.dataSource = dataSource;
 		}
 

spring-boot-project/spring-boot-docs/src/docs/asciidoc/howto/batch.adoc

@@ -3,6 +3,19 @@
 A number of questions often arise when people use Spring Batch from within a Spring Boot application.
 This section addresses those questions.
 
+[[howto.batch.architectural-considerations]]
+=== Architectural Considerations
+
+The default configuration of Spring Batch is geared towards single-job containerized Spring Boot apps orchestrated by a job scheduler like Kubernetes, optionally using https://dataflow.spring.io/[Spring Cloud Dataflow]:
+
+* All `Jobs` in the application context are executed once on application startup; see <<#howto.batch.running-jobs-on-startup>>.
+* Jobs are run on the same thread they are launched on.
+
+However, it is also a valid option to run batch jobs as part of other applications, notably web applications running in servlet containers.
+Example use cases include reporting, ad-hoc job running, and web application support.
+See {spring-batch-docs}job.html#runningJobsFromWebContainer[the Spring Batch documentation] for how to do this.
+You might need to <<#howto.batch.customizing-task-executor,customize the task executor for batch jobs>> if you opt for this approach.
+
 
 
 [[howto.batch.specifying-a-data-source]]
@@ -57,3 +70,20 @@ This provides only one argument to the batch job: `someParameter=someValue`.
 Spring Batch requires a data store for the `Job` repository.
 If you use Spring Boot, you must use an actual database.
 Note that it can be an in-memory database, see {spring-batch-docs}job.html#configuringJobRepository[Configuring a Job Repository].
+
+[[howto.batch.customizing-task-executor]]
+=== Customizing the TaskExecutor for Batch Jobs
+
+By default, jobs are run on the same thread they are launched on.
+See {spring-batch-api}/core/configuration/annotation/EnableBatchProcessing.html[the Javadoc of `@EnableBatchProcessing`] for details.
+Depending on your type of application, this might be undesirable because the starting thread is blocked while the batch job runs.
+Furthermore, additional jobs might have to wait for the currently running job to complete.
+In such a case, it is necessary to customize the `TaskExecutor` used by Spring Batch.
+The auto-configuration of Spring Batch automatically picks up any `TaskExecutor` annotated with `@BatchTaskExecutor`, for example:
+
+[source,java,indent=0,subs="verbatim"]
+----
+include::{docs-java}/howto/batch/customizingtaskexecutor/BatchConfiguration.java[tag=bean]
+----
+
+The example configures a `TaskExecutor` that dynamically adapts it size and uses up to 4 threads with a maximum queue size of 10. Adjust this configuration to match the needs of your application.

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/howto/batch/customizingtaskexecutor/BatchConfiguration.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2022 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.boot.docs.howto.batch.customizingtaskexecutor;
+
+import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
+import org.springframework.boot.autoconfigure.batch.BatchTaskExecutor;
+import org.springframework.boot.task.TaskExecutorBuilder;
+import org.springframework.context.annotation.Bean;
+import org.springframework.core.task.TaskExecutor;
+
+@EnableBatchProcessing
+public class BatchConfiguration {
+
+	// tag::bean[]
+	@Bean
+	@BatchTaskExecutor
+	public TaskExecutor batchTaskExecutor(TaskExecutorBuilder builder) {
+		return builder.threadNamePrefix("batch-").corePoolSize(0).maxPoolSize(4).queueCapacity(10)
+				.allowCoreThreadTimeOut(true).awaitTermination(false).build();
+	}
+	// end::bean[]
+
+}