BATCH-2537: add support for @Primary annotated data sources

Currently, when multiple data sources are defined in the context, an
IllegalStateException is thrown even if one of the data sources is
annotated with @Primary (which should be the one to use).

This commit makes it possible to use the data source annotated with
@Primary when multiple data sources are defined. Note that the context
initialization will still fail (with a UnsatisfiedDependencyException
from Spring's bean factory) if multiple data sources are defined and
none of them is annotated with @Primary. If multiple data sources are
defined and none of them is annotated with @Primary but one of them is
named "dataSource", this data source will be used by the batch
configuration due to autowiring by name (this detail has been documented
in the javadoc of @EnableBatchProcessing).

Resolves BATCH-2537

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

@@ -33,9 +33,11 @@ import org.springframework.batch.core.repository.JobRepository;
 import org.springframework.batch.core.scope.context.ChunkContext;
 import org.springframework.batch.core.step.tasklet.Tasklet;
 import org.springframework.batch.repeat.RepeatStatus;
+import org.springframework.beans.factory.UnsatisfiedDependencyException;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Primary;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
 import org.springframework.stereotype.Component;
@@ -57,11 +59,21 @@ public class MapJobRepositoryConfigurationTests {
 		testConfigurationClass(HsqlBatchConfiguration.class);
 	}
 
-	@Test(expected = IllegalStateException.class)
-	public void testMultipleDataSources() throws Exception {
+	@Test(expected = UnsatisfiedDependencyException.class)
+	public void testMultipleDataSources_whenNoneOfThemIsPrimary() throws Exception {
 		testConfigurationClass(InvalidBatchConfiguration.class);
 	}
 
+	@Test
+	public void testMultipleDataSources_whenNoneOfThemIsPrimaryButOneOfThemIsNamed_dataSource_() throws Exception {
+		testConfigurationClass(ValidBatchConfigurationWithoutPrimaryDataSource.class);
+	}
+
+	@Test
+	public void testMultipleDataSources_whenOneOfThemIsPrimary() throws Exception {
+		testConfigurationClass(ValidBatchConfigurationWithPrimaryDataSource.class);
+	}
+
 	private void testConfigurationClass(Class<?> clazz) throws Exception {
 		GenericApplicationContext context = new AnnotationConfigApplicationContext(clazz);
 		this.jobLauncher = context.getBean(JobLauncher.class);
@@ -85,11 +97,37 @@ public class MapJobRepositoryConfigurationTests {
 		}
 	}
 
+	public static class ValidBatchConfigurationWithPrimaryDataSource extends HsqlBatchConfiguration {
+
+		@Primary
+		@Bean
+		DataSource dataSource2() {
+			return new PooledEmbeddedDataSource(new EmbeddedDatabaseBuilder().
+					setName("dataSource2").
+					addScript("classpath:org/springframework/batch/core/schema-drop-hsqldb.sql").
+					addScript("classpath:org/springframework/batch/core/schema-hsqldb.sql").
+					build());
+		}
+	}
+
+	public static class ValidBatchConfigurationWithoutPrimaryDataSource extends HsqlBatchConfiguration {
+
+		@Bean
+		DataSource dataSource() { // will be autowired by name
+			return new PooledEmbeddedDataSource(new EmbeddedDatabaseBuilder().
+					setName("dataSource").
+					addScript("classpath:org/springframework/batch/core/schema-drop-hsqldb.sql").
+					addScript("classpath:org/springframework/batch/core/schema-hsqldb.sql").
+					build());
+		}
+	}
+
 	public static class HsqlBatchConfiguration extends MapRepositoryBatchConfiguration {
 
 		@Bean
-		DataSource dataSource() {
+		DataSource dataSource1() {
 			return new PooledEmbeddedDataSource(new EmbeddedDatabaseBuilder().
+					setName("dataSource1").
 				addScript("classpath:org/springframework/batch/core/schema-drop-hsqldb.sql").
 				addScript("classpath:org/springframework/batch/core/schema-hsqldb.sql").
 				build());