Set isolation to DEFAULT for JPA transaction manager

Also logs a warning about the fact that locks may not be taken when
starting a Job. JPA and Batch don't really work that well together
in general so it's probably not worth a lot of effort to work aoround
this. If anyone needs to they should create a custom JpaDialect
(and a BatchConfigurer).

Fixes gh-197

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

@@ -20,6 +20,8 @@ import javax.annotation.PostConstruct;
 import javax.persistence.EntityManagerFactory;
 import javax.sql.DataSource;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.springframework.batch.core.configuration.annotation.BatchConfigurer;
 import org.springframework.batch.core.launch.JobLauncher;
 import org.springframework.batch.core.launch.support.SimpleJobLauncher;
@@ -36,6 +38,8 @@ import org.springframework.transaction.PlatformTransactionManager;
 @Component
 public class BasicBatchConfigurer implements BatchConfigurer {
 
+	private static Log logger = LogFactory.getLog(BasicBatchConfigurer.class);
+
 	private DataSource dataSource;
 	private EntityManagerFactory entityManagerFactory;
 	private PlatformTransactionManager transactionManager;
@@ -84,6 +88,10 @@ public class BasicBatchConfigurer implements BatchConfigurer {
 	protected JobRepository createJobRepository() throws Exception {
 		JobRepositoryFactoryBean factory = new JobRepositoryFactoryBean();
 		factory.setDataSource(this.dataSource);
+		if (this.entityManagerFactory != null) {
+			logger.warn("JPA does not support custom isolation levels, so locks may not be taken when launching Jobs");
+			factory.setIsolationLevelForCreate("ISOLATION_DEFAULT");
+		}
 		factory.setTransactionManager(getTransactionManager());
 		factory.afterPropertiesSet();
 		return (JobRepository) factory.getObject();

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

@@ -54,6 +54,7 @@ import org.springframework.transaction.PlatformTransactionManager;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 /**
@@ -143,6 +144,9 @@ public class BatchAutoConfigurationTests {
 		// It's a lazy proxy, but it does render its target if you ask for toString():
 		assertTrue(transactionManager.toString().contains("JpaTransactionManager"));
 		assertNotNull(this.context.getBean(EntityManagerFactory.class));
+		// Ensure the JobRepository can be used (no problem with isolation level)
+		assertNull(this.context.getBean(JobRepository.class).getLastJobExecution("job",
+				new JobParameters()));
 	}
 
 	@EnableBatchProcessing