Add customizer for conversion service used by Spring Batch

See gh-34769

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure.batch;
 
+import java.util.List;
+
 import javax.sql.DataSource;
 
 import org.springframework.batch.core.configuration.ListableJobLocator;
@@ -44,6 +46,7 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Conditional;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.core.convert.support.ConfigurableConversionService;
 import org.springframework.jdbc.datasource.init.DatabasePopulator;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.annotation.Isolation;
@@ -115,11 +118,15 @@ public class BatchAutoConfiguration {
 
 		private final BatchProperties properties;
 
+		private final List<BatchConversionServiceCustomizer> batchConversionServiceCustomizers;
+
 		SpringBootBatchConfiguration(DataSource dataSource, @BatchDataSource ObjectProvider<DataSource> batchDataSource,
-				PlatformTransactionManager transactionManager, BatchProperties properties) {
+				PlatformTransactionManager transactionManager, BatchProperties properties,
+				List<BatchConversionServiceCustomizer> batchConversionServiceCustomizers) {
 			this.dataSource = batchDataSource.getIfAvailable(() -> dataSource);
 			this.transactionManager = transactionManager;
 			this.properties = properties;
+			this.batchConversionServiceCustomizers = batchConversionServiceCustomizers;
 		}
 
 		@Override
@@ -144,6 +151,15 @@ public class BatchAutoConfiguration {
 			return (isolation != null) ? isolation : super.getIsolationLevelForCreate();
 		}
 
+		@Override
+		protected ConfigurableConversionService getConversionService() {
+			ConfigurableConversionService conversionService = super.getConversionService();
+			for (BatchConversionServiceCustomizer customizer : this.batchConversionServiceCustomizers) {
+				customizer.customize(conversionService);
+			}
+			return conversionService;
+		}
+
 	}
 
 	@Configuration(proxyBeanMethods = false)

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

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2023 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 org.springframework.core.convert.support.ConfigurableConversionService;
+
+/**
+ * Callback interface that can be implemented by beans wishing to further customize the
+ * {@link ConfigurableConversionService} used in
+ * {@link org.springframework.batch.core.configuration.support.DefaultBatchConfiguration}
+ * retaining its default auto-configuration.
+ *
+ * @author Claudio Nave
+ * @since 3.1.0
+ */
+@FunctionalInterface
+public interface BatchConversionServiceCustomizer {
+
+	/**
+	 * Customize the {@link ConfigurableConversionService}.
+	 * @param configurableConversionService the ConfigurableConversionService to customize
+	 */
+	void customize(ConfigurableConversionService configurableConversionService);
+
+}

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

@@ -71,6 +71,8 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Primary;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.core.convert.support.ConfigurableConversionService;
 import org.springframework.jdbc.BadSqlGrammarException;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.jdbc.datasource.DataSourceTransactionManager;
@@ -400,6 +402,21 @@ class BatchAutoConfigurationTests {
 				.hasBean("customInitializer"));
 	}
 
+	@Test
+	void userProvidedCustomConverter() {
+		this.contextRunner.withUserConfiguration(TestConfiguration.class, EmbeddedDataSourceConfiguration.class)
+			.withUserConfiguration(RegisterCustomConverter.class)
+			.run((context) -> {
+				assertThat(context).hasSingleBean(SpringBootBatchConfiguration.class);
+				ConfigurableConversionService configurableConversionService = context
+					.getBean(SpringBootBatchConfiguration.class)
+					.getConversionService();
+				assertThat(configurableConversionService.canConvert(RegisterCustomConverter.Foo.class,
+						RegisterCustomConverter.Bar.class))
+					.isTrue();
+			});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	protected static class BatchDataSourceConfiguration {
 
@@ -680,4 +697,32 @@ class BatchAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class RegisterCustomConverter {
+
+		@Bean
+		BatchConversionServiceCustomizer batchConversionServiceCustomizer() {
+			return (configurableConversionService) -> configurableConversionService
+				.addConverter(new FooToBarConverter());
+		}
+
+		static class Foo {
+
+		}
+
+		static class Bar {
+
+		}
+
+		static class FooToBarConverter implements Converter<Foo, Bar> {
+
+			@Override
+			public Bar convert(Foo source) {
+				return null;
+			}
+
+		}
+
+	}
+
 }