Fix #5340: Allow restart of jobs with JobParameterIncrementer from command line

This commit addresses the issue where jobs using JobParameterIncrementer
could not be restarted from the command line. Previously, the start()
method would always use the incrementer to create a new instance, even
when there was a failed/stopped job instance that could be restarted.

Changes:
- Modified SimpleJobOperator.start() to first try running the job with
  provided parameters (which restarts failed/stopped instances)
- Only use the incrementer when JobInstanceAlreadyCompleteException
  is thrown (meaning the job instance is already complete)

This allows jobs with JobParameterIncrementer to be restarted from the
command line when they fail or stop, while still creating new instances
when the previous instance is complete.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nikitanagar08

spring-batch-core/src/main/java/org/springframework/batch/core/launch/support/SimpleJobOperator.java

@@ -172,8 +172,10 @@ public Long start(String jobName, Properties parameters)
 
 	/**
 	 * Start a new instance of a job with the specified parameters. If the job defines a
-	 * {@link JobParametersIncrementer}, then the incrementer will be used to calculate
-	 * the next parameters in the sequence and the provided parameters will be ignored.
+	 * {@link JobParametersIncrementer} and there is no restartable job instance for the
+	 * provided parameters, then the incrementer will be used to calculate the next
+	 * parameters in the sequence. Otherwise, the job will be launched (or restarted) with
+	 * the provided parameters.
 	 * @param job the {@link Job} to start
 	 * @param jobParameters the {@link JobParameters} to start the job with
 	 * @return the {@link JobExecution} that was started
@@ -191,12 +193,21 @@ public JobExecution start(Job job, JobParameters jobParameters) throws JobInstan
 		Assert.notNull(job, "The Job must not be null.");
 		Assert.notNull(jobParameters, "The JobParameters must not be null.");
 		if (job.getJobParametersIncrementer() != null) {
-			if (!jobParameters.isEmpty() && logger.isWarnEnabled()) {
-				logger.warn(String.format(
-						"Attempting to launch job: [%s] which defines an incrementer with additional parameters: [%s]. Additional parameters will be ignored.",
-						job.getName(), jobParameters));
+			// First, try to run the job with the provided parameters.
+			// This will restart failed/stopped job instances if they exist.
+			try {
+				return run(job, jobParameters);
+			}
+			catch (JobInstanceAlreadyCompleteException e) {
+				// Job instance with these parameters is already complete.
+				// Use the incrementer to get the next parameters for a new instance.
+				if (!jobParameters.isEmpty() && logger.isWarnEnabled()) {
+					logger.warn(String.format(
+							"Job instance for [%s] with parameters [%s] is already complete. Using incrementer to get next parameters.",
+							job.getName(), jobParameters));
+				}
+				return startNextInstance(job);
 			}
-			return startNextInstance(job);
 		}
 		return run(job, jobParameters);
 	}