added assert to JobInstanceDao#createJobInstance(Job, JobParameters) that JobInstance does not already exist

spring-batch-execution/src/main/java/org/springframework/batch/execution/repository/dao/JdbcJobInstanceDao.java

@@ -57,6 +57,8 @@ public class JdbcJobInstanceDao extends AbstractJdbcBatchMetadataDao implements
 		Assert.hasLength(job.getName(), "Job must have a name");
 		Assert.notNull(jobParameters, "JobParameters must not be null.");
 
+		Assert.state(getJobInstance(job, jobParameters) == null, "JobInstance must not already exist");
+		
 		Long jobId = new Long(jobIncrementer.nextLongValue());
 		Object[] parameters = new Object[] { jobId, job.getName(), createJobKey(jobParameters) };
 		getJdbcTemplate().update(getQuery(CREATE_JOB_INSTANCE), parameters,

spring-batch-execution/src/main/java/org/springframework/batch/execution/repository/dao/JobInstanceDao.java

@@ -1,7 +1,5 @@
 package org.springframework.batch.execution.repository.dao;
 
-import java.util.List;
-
 import org.springframework.batch.core.domain.Job;
 import org.springframework.batch.core.domain.JobInstance;
 import org.springframework.batch.core.domain.JobParameters;
@@ -18,7 +16,9 @@ public interface JobInstanceDao {
 	/**
 	 * Create a JobInstance with given name and parameters.
 	 * 
-	 * PostConditions: A valid job will be returned which has been persisted and
+	 * PreConditions: JobInstance for given name and parameters must not already exist
+	 * 
+	 * PostConditions: A valid job instancewill be returned which has been persisted and
 	 * contains an unique Id.
 	 * 
 	 * @param jobName

spring-batch-execution/src/main/java/org/springframework/batch/execution/repository/dao/MapJobInstanceDao.java

@@ -7,6 +7,7 @@ import org.springframework.batch.core.domain.Job;
 import org.springframework.batch.core.domain.JobInstance;
 import org.springframework.batch.core.domain.JobParameters;
 import org.springframework.batch.support.transaction.TransactionAwareProxyFactory;
+import org.springframework.util.Assert;
 
 public class MapJobInstanceDao implements JobInstanceDao {
 
@@ -20,9 +21,7 @@ public class MapJobInstanceDao implements JobInstanceDao {
 
 	public JobInstance createJobInstance(Job job, JobParameters jobParameters) {
 		
-		if (getJobInstance(job, jobParameters) != null) {
-			throw new IllegalArgumentException("JobInstance already exists for given job and parameters");
-		}
+		Assert.state(getJobInstance(job, jobParameters) == null, "JobInstance must not already exist");
 		
 		JobInstance jobInstance = new JobInstance(new Long(currentId++), jobParameters, job);
 		jobInstances.add(jobInstance);

spring-batch-execution/src/test/java/org/springframework/batch/execution/repository/dao/AbstractJobDaoTests.java

@@ -268,4 +268,22 @@ public abstract class AbstractJobDaoTests extends AbstractTransactionalDataSourc
 
 		assertEquals(lastExecution, jobExecutionDao.getLastJobExecution(jobInstance));
 	}
+	
+	/**
+	 * Trying to create instance twice for the same job+parameters causes error
+	 */
+	public void testCreateDuplicateInstance() {
+		
+		jobParameters = new JobParameters();
+		
+		jobInstanceDao.createJobInstance(job, jobParameters);
+		
+		try {
+			jobInstanceDao.createJobInstance(job, jobParameters);
+			fail();
+		}
+		catch (IllegalStateException e) {
+			// expected
+		}
+	}
 }

spring-batch-execution/src/test/java/org/springframework/batch/execution/repository/dao/MapJobInstanceDaoTests.java

@@ -10,8 +10,12 @@ import org.springframework.batch.execution.job.JobSupport;
 
 public class MapJobInstanceDaoTests extends TestCase {
 
-	JobInstanceDao dao = new MapJobInstanceDao();
-	
+	private JobInstanceDao dao = new MapJobInstanceDao();
+
+	private Job fooJob = new JobSupport("foo");
+
+	private JobParameters fooParams = new JobParametersBuilder().addString("fooKey", "fooValue").toJobParameters();
+
 	protected void setUp() throws Exception {
 		MapJobInstanceDao.clear();
 	}
@@ -24,15 +28,29 @@ public class MapJobInstanceDaoTests extends TestCase {
 	 * Create and retrieve a job instance.
 	 */
 	public void testCreateAndRetrieve() throws Exception {
-		Job fooJob = new JobSupport("foo");
-		JobParameters fooParams = new JobParametersBuilder().addString("fooKey", "fooValue").toJobParameters();
-		
+
 		JobInstance fooInstance = dao.createJobInstance(fooJob, fooParams);
 		assertNotNull(fooInstance.getId());
 		assertEquals(fooJob, fooInstance.getJob());
 		assertEquals(fooParams, fooInstance.getJobParameters());
-		
+
 		JobInstance retrievedInstance = dao.getJobInstance(fooJob, fooParams);
 		assertEquals(fooInstance, retrievedInstance);
 	}
+
+	/**
+	 * Trying to create instance twice for the same job+parameters causes error
+	 */
+	public void testCreateDuplicateInstance() {
+		
+		dao.createJobInstance(fooJob, fooParams);
+		
+		try {
+			dao.createJobInstance(fooJob, fooParams);
+			fail();
+		}
+		catch (IllegalStateException e) {
+			// expected
+		}
+	}
 }