Improve the process of job registration

This commit changes the way of populating the default
job registry from using a BeanPostProcessor to using
a JobRegistrySmartInitializingSingleton. This change
resolves warnings about beans being eagerly injected
into currently created BeanPostProcessors and prevents
lifecycle issues about early bean initializations.

It also deprecates JobRegistryBeanPostProcessor in favor
of JobRegistrySmartInitializingSingleton.

Resolves #4547

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/annotation/BatchRegistrar.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2023 the original author or authors.
+ * Copyright 2022-2024 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.
@@ -22,7 +22,7 @@ import org.apache.commons.logging.LogFactory;
 
 import org.springframework.batch.core.configuration.support.AutomaticJobRegistrar;
 import org.springframework.batch.core.configuration.support.DefaultJobLoader;
-import org.springframework.batch.core.configuration.support.JobRegistryBeanPostProcessor;
+import org.springframework.batch.core.configuration.support.JobRegistrySmartInitializingSingleton;
 import org.springframework.batch.core.configuration.support.MapJobRegistry;
 import org.springframework.batch.core.explore.support.JobExplorerFactoryBean;
 import org.springframework.batch.core.launch.support.JobOperatorFactoryBean;
@@ -63,7 +63,7 @@ class BatchRegistrar implements ImportBeanDefinitionRegistrar {
 		registerJobExplorer(registry, batchAnnotation);
 		registerJobLauncher(registry, batchAnnotation);
 		registerJobRegistry(registry);
-		registerJobRegistryBeanPostProcessor(registry);
+		registerJobRegistrySmartInitializingSingleton(registry);
 		registerJobOperator(registry, batchAnnotation);
 		registerAutomaticJobRegistrar(registry, batchAnnotation);
 		watch.stop();
@@ -225,17 +225,19 @@ class BatchRegistrar implements ImportBeanDefinitionRegistrar {
 		registry.registerBeanDefinition("jobRegistry", beanDefinition);
 	}
 
-	private void registerJobRegistryBeanPostProcessor(BeanDefinitionRegistry registry) {
-		if (registry.containsBeanDefinition("jobRegistryBeanPostProcessor")) {
-			LOGGER.info("Bean jobRegistryBeanPostProcessor already defined in the application context, skipping"
-					+ " the registration of a jobRegistryBeanPostProcessor");
+	private void registerJobRegistrySmartInitializingSingleton(BeanDefinitionRegistry registry) {
+		if (registry.containsBeanDefinition("jobRegistrySmartInitializingSingleton")) {
+			LOGGER
+				.info("Bean jobRegistrySmartInitializingSingleton already defined in the application context, skipping"
+						+ " the registration of a jobRegistrySmartInitializingSingleton");
 			return;
 		}
 		BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder
-			.genericBeanDefinition(JobRegistryBeanPostProcessor.class);
+			.genericBeanDefinition(JobRegistrySmartInitializingSingleton.class);
 		beanDefinitionBuilder.addPropertyReference("jobRegistry", "jobRegistry");
 
-		registry.registerBeanDefinition("jobRegistryBeanPostProcessor", beanDefinitionBuilder.getBeanDefinition());
+		registry.registerBeanDefinition("jobRegistrySmartInitializingSingleton",
+				beanDefinitionBuilder.getBeanDefinition());
 	}
 
 	private void registerJobOperator(BeanDefinitionRegistry registry, EnableBatchProcessing batchAnnotation) {

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/annotation/EnableBatchProcessing.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -93,9 +93,9 @@ import org.springframework.transaction.PlatformTransactionManager;
  * "jobOperator" of type
  * {@link org.springframework.batch.core.launch.support.SimpleJobOperator})</li>
  * <li>a
- * {@link org.springframework.batch.core.configuration.support.JobRegistryBeanPostProcessor}
- * (bean name "jobRegistryBeanPostProcessor" of type
- * {@link org.springframework.batch.core.configuration.support.JobRegistryBeanPostProcessor})</li>
+ * {@link org.springframework.batch.core.configuration.support.JobRegistrySmartInitializingSingleton}
+ * (bean name "jobRegistrySmartInitializingSingleton" of type
+ * {@link org.springframework.batch.core.configuration.support.JobRegistrySmartInitializingSingleton})</li>
  * </ul>
  *
  * If the configuration is specified as <code>modular=true</code>, the context also

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/DefaultBatchConfiguration.java

@@ -251,24 +251,12 @@ public class DefaultBatchConfiguration implements ApplicationContextAware {
 	 * @return a {@link JobRegistryBeanPostProcessor}
 	 * @throws BatchConfigurationException if unable to register the bean
 	 * @since 5.1
-	 * @deprecated Use {@link #jobRegistryBeanPostProcessor(JobRegistry)} instead
+	 * @deprecated Use {@link #jobRegistrySmartInitializingSingleton(JobRegistry)} instead
 	 */
 	@Deprecated(forRemoval = true)
 	public JobRegistryBeanPostProcessor jobRegistryBeanPostProcessor() throws BatchConfigurationException {
-		return jobRegistryBeanPostProcessor(jobRegistry());
-	}
-
-	/**
-	 * Defines a {@link JobRegistryBeanPostProcessor} bean.
-	 * @return a {@link JobRegistryBeanPostProcessor} bean
-	 * @throws BatchConfigurationException if unable to register the bean
-	 * @since 5.2
-	 */
-	@Bean
-	public JobRegistryBeanPostProcessor jobRegistryBeanPostProcessor(JobRegistry jobRegistry)
-			throws BatchConfigurationException {
 		JobRegistryBeanPostProcessor jobRegistryBeanPostProcessor = new JobRegistryBeanPostProcessor();
-		jobRegistryBeanPostProcessor.setJobRegistry(jobRegistry);
+		jobRegistryBeanPostProcessor.setJobRegistry(jobRegistry());
 		try {
 			jobRegistryBeanPostProcessor.afterPropertiesSet();
 			return jobRegistryBeanPostProcessor;
@@ -278,6 +266,28 @@ public class DefaultBatchConfiguration implements ApplicationContextAware {
 		}
 	}
 
+	/**
+	 * Define a {@link JobRegistrySmartInitializingSingleton} bean.
+	 * @param jobRegistry the job registry to populate
+	 * @throws BatchConfigurationException if unable to register the bean
+	 * @return a bean of type {@link JobRegistrySmartInitializingSingleton}
+	 * @since 5.2
+	 */
+	@Bean
+	public JobRegistrySmartInitializingSingleton jobRegistrySmartInitializingSingleton(JobRegistry jobRegistry)
+			throws BatchConfigurationException {
+		JobRegistrySmartInitializingSingleton jobRegistrySmartInitializingSingleton = new JobRegistrySmartInitializingSingleton();
+		jobRegistrySmartInitializingSingleton.setJobRegistry(jobRegistry);
+		try {
+			jobRegistrySmartInitializingSingleton.afterPropertiesSet();
+			return jobRegistrySmartInitializingSingleton;
+		}
+		catch (Exception e) {
+			throw new BatchConfigurationException(
+					"Unable to configure the default job registry SmartInitializingSingleton", e);
+		}
+	}
+
 	/*
 	 * Getters to customize the configuration of infrastructure beans
 	 */

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/JobRegistryBeanPostProcessor.java

@@ -45,10 +45,13 @@ import org.springframework.util.Assert;
  * recommended in cases where this class may cause early bean initializations. You must
  * include at most one of either of them as a bean.
  *
+ * @deprecated since 5.2 in favor of {@link JobRegistrySmartInitializingSingleton}.
+ *
  * @author Dave Syer
  * @author Mahmoud Ben Hassine
  *
  */
+@Deprecated(since = "5.2")
 public class JobRegistryBeanPostProcessor
 		implements BeanPostProcessor, BeanFactoryAware, InitializingBean, DisposableBean {
 

spring-batch-core/src/test/java/org/springframework/batch/core/configuration/annotation/BatchRegistrarTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2023 the original author or authors.
+ * Copyright 2022-2024 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.
@@ -27,7 +27,7 @@ import org.springframework.aop.framework.Advised;
 import org.springframework.batch.core.DefaultJobKeyGenerator;
 import org.springframework.batch.core.JobKeyGenerator;
 import org.springframework.batch.core.configuration.JobRegistry;
-import org.springframework.batch.core.configuration.support.JobRegistryBeanPostProcessor;
+import org.springframework.batch.core.configuration.support.JobRegistrySmartInitializingSingleton;
 import org.springframework.batch.core.explore.JobExplorer;
 import org.springframework.batch.core.launch.JobLauncher;
 import org.springframework.batch.core.launch.JobOperator;
@@ -79,7 +79,7 @@ class BatchRegistrarTests {
 		Assertions.assertTrue(Mockito.mockingDetails(context.getBean(JobLauncher.class)).isMock());
 		Assertions.assertTrue(Mockito.mockingDetails(context.getBean(JobRegistry.class)).isMock());
 		Assertions.assertTrue(Mockito.mockingDetails(context.getBean(JobOperator.class)).isMock());
-		Assertions.assertTrue(Mockito.mockingDetails(context.getBean(JobRegistryBeanPostProcessor.class)).isMock());
+		Assertions.assertTrue(Mockito.mockingDetails(context.getBean(JobRegistrySmartInitializingSingleton.class)).isMock());
 	}
 
 	@Test
@@ -162,7 +162,8 @@ class BatchRegistrarTests {
 		JobExplorer jobExplorer = context.getBean(JobExplorer.class);
 		JobRegistry jobRegistry = context.getBean(JobRegistry.class);
 		JobOperator jobOperator = context.getBean(JobOperator.class);
-		JobRegistryBeanPostProcessor jobRegistryBeanPostProcessor = context.getBean(JobRegistryBeanPostProcessor.class);
+		JobRegistrySmartInitializingSingleton jobRegistrySmartInitializingSingleton = context
+			.getBean(JobRegistrySmartInitializingSingleton.class);
 
 		// then
 		Assertions.assertNotNull(jobLauncher);
@@ -170,7 +171,7 @@ class BatchRegistrarTests {
 		Assertions.assertNotNull(jobExplorer);
 		Assertions.assertNotNull(jobRegistry);
 		Assertions.assertNotNull(jobOperator);
-		Assertions.assertNotNull(jobRegistryBeanPostProcessor);
+		Assertions.assertNotNull(jobRegistrySmartInitializingSingleton);
 	}
 
 	@Test
@@ -249,7 +250,7 @@ class BatchRegistrarTests {
 		}
 
 		@Bean
-		public JobRegistryBeanPostProcessor jobRegistryBeanPostProcessor() {
+		public JobRegistrySmartInitializingSingleton jobRegistrySmartInitializingSingleton() {
 			return Mockito.mock();
 		}
 

spring-batch-core/src/test/java/org/springframework/batch/core/configuration/support/DefaultBatchConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022-2023 the original author or authors.
+ * Copyright 2022-2024 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.
@@ -85,9 +85,9 @@ class DefaultBatchConfigurationTests {
 		Assertions.assertEquals(1, jobRepositories.size());
 		JobRepository jobRepository = jobRepositories.entrySet().iterator().next().getValue();
 		Assertions.assertInstanceOf(DummyJobRepository.class, jobRepository);
-		Map<String, JobRegistryBeanPostProcessor> jobRegistryBeanPostProcessorMap = context
-			.getBeansOfType(JobRegistryBeanPostProcessor.class);
-		Assertions.assertEquals(1, jobRegistryBeanPostProcessorMap.size());
+		Map<String, JobRegistrySmartInitializingSingleton> jobRegistrySmartInitializingSingletonMap = context
+			.getBeansOfType(JobRegistrySmartInitializingSingleton.class);
+		Assertions.assertEquals(1, jobRegistrySmartInitializingSingletonMap.size());
 	}
 
 	@Test
@@ -101,7 +101,8 @@ class DefaultBatchConfigurationTests {
 		JobExplorer jobExplorer = context.getBean(JobExplorer.class);
 		JobRegistry jobRegistry = context.getBean(JobRegistry.class);
 		JobOperator jobOperator = context.getBean(JobOperator.class);
-		JobRegistryBeanPostProcessor jobRegistryBeanPostProcessor = context.getBean(JobRegistryBeanPostProcessor.class);
+		JobRegistrySmartInitializingSingleton jobRegistrySmartInitializingSingleton = context
+			.getBean(JobRegistrySmartInitializingSingleton.class);
 
 		// then
 		Assertions.assertNotNull(jobLauncher);
@@ -109,7 +110,7 @@ class DefaultBatchConfigurationTests {
 		Assertions.assertNotNull(jobExplorer);
 		Assertions.assertNotNull(jobRegistry);
 		Assertions.assertNotNull(jobOperator);
-		Assertions.assertNotNull(jobRegistryBeanPostProcessor);
+		Assertions.assertNotNull(jobRegistrySmartInitializingSingleton);
 	}
 
 	@Configuration
@@ -161,10 +162,10 @@ class DefaultBatchConfigurationTests {
 		}
 
 		@Bean
-		public JobRegistryBeanPostProcessor jobRegistryBeanPostProcessor(JobRegistry jobRegistry) {
-			JobRegistryBeanPostProcessor postProcessor = new JobRegistryBeanPostProcessor();
-			postProcessor.setJobRegistry(jobRegistry);
-			return postProcessor;
+		public JobRegistrySmartInitializingSingleton jobRegistrySmartInitializingSingleton(JobRegistry jobRegistry) {
+			JobRegistrySmartInitializingSingleton smartInitializingSingleton = new JobRegistrySmartInitializingSingleton();
+			smartInitializingSingleton.setJobRegistry(jobRegistry);
+			return smartInitializingSingleton;
 		}
 
 	}

spring-batch-docs/modules/ROOT/pages/job/advanced-meta-data.adoc

@@ -222,7 +222,12 @@ example has been given an `id` so that it can be included in child
 contexts (for example, as a parent bean definition) and cause all jobs created
 there to also be registered automatically.
 
-As of version 5.1, the `@EnableBatchProcessing` annotation automatically registers a `jobRegistryBeanPostProcessor` bean in the application context.
+[WARNING]
+.Deprecation
+====
+As of version 5.2, the `JobRegistryBeanPostProcessor` class is deprecated in favor of
+`JobRegistrySmartInitializingSingleton`, see xref:#jobregistrysmartinitializingsingleton[JobRegistrySmartInitializingSingleton].
+====
 
 [[jobregistrysmartinitializingsingleton]]
 === JobRegistrySmartInitializingSingleton