Add ExitStatus overload for on() method in builder classes

Introduce on(ExitStatus) method in builder classes for better type safety

Fixes [#5306](#5306)

Add on(ExitStatus) methods as overloaded convenience methods that delegate directly to the existing on(String) methods by extracting the underlying exit code. The new method names make the type-safe behavior explicit and improve API consistency across builder classes.

Changes:
- `SimpleJobBuilder.on(ExitStatus)` - delegates to on(String)
- `FlowBuilder.on(ExitStatus)` - delegates to on(String)
- `FlowBuilder.UnterminatedFlowBuilder.on(ExitStatus)` - delegates to on(String)

The existing on(String) methods remain for backward compatibility and to preserve wildcard pattern matching.

Signed-off-by: Taha Yigit Melek <yigittahamelek@gmail.com>

Author: tahayigitmelek

spring-batch-core/src/main/java/org/springframework/batch/core/job/builder/FlowBuilder.java

@@ -224,6 +224,16 @@ public TransitionBuilder<Q> on(String pattern) {
 		return new TransitionBuilder<>(this, pattern);
 	}
 
+	/**
+	 * Start a transition to a new state if the exit status from the previous state
+	 * matches the status given.
+	 * @param status the exit status on which to take this transition
+	 * @return a builder to enable fluent chaining
+	 */
+	public TransitionBuilder<Q> on(ExitStatus status) {
+		return on(status.getExitCode());
+	}
+
 	/**
 	 * A synonym for {@link #build()} which callers might find useful. Subclasses can
 	 * override build to create an object of the desired type (e.g. a parent builder or an
@@ -437,6 +447,16 @@ public TransitionBuilder<Q> on(String pattern) {
 			return new TransitionBuilder<>(parent, pattern);
 		}
 
+		/**
+		 * Start a transition to a new state if the exit status from the previous state
+		 * matches the status given.
+		 * @param status the exit status on which to take this transition
+		 * @return a TransitionBuilder
+		 */
+		public TransitionBuilder<Q> on(ExitStatus status) {
+			return on(status.getExitCode());
+		}
+
 	}
 
 	/**

spring-batch-core/src/main/java/org/springframework/batch/core/job/builder/SimpleJobBuilder.java

@@ -20,6 +20,7 @@
 
 import org.jspecify.annotations.NullUnmarked;
 
+import org.springframework.batch.core.ExitStatus;
 import org.springframework.batch.core.job.Job;
 import org.springframework.batch.core.step.Step;
 import org.springframework.batch.core.job.SimpleJob;
@@ -99,6 +100,15 @@ public FlowBuilder.TransitionBuilder<FlowJobBuilder> on(String pattern) {
 		return builder.on(pattern);
 	}
 
+	/**
+	 * Branch into a flow conditional on the outcome of the current step.
+	 * @param status the exit status of the current step
+	 * @return a builder for fluent chaining
+	 */
+	public FlowBuilder.TransitionBuilder<FlowJobBuilder> on(ExitStatus status) {
+		return on(status.getExitCode());
+	}
+
 	/**
 	 * Start with this decider. Returns a flow builder and when the flow is ended a job
 	 * builder will be returned to continue the job configuration if needed.

spring-batch-core/src/test/java/org/springframework/batch/core/job/builder/FlowBuilderTests.java

@@ -166,6 +166,49 @@ public void execute(StepExecution stepExecution) throws UnexpectedJobExecutionEx
 		assertFalse(stepExecutions.hasNext());
 	}
 
+	@Test
+	void testOnExitStatus() throws Exception {
+		FlowBuilder<Flow> builder = new FlowBuilder<>("transitionsFlow");
+		JobRepository jobRepository = new ResourcelessJobRepository();
+		JobParameters jobParameters = new JobParameters();
+		JobInstance jobInstance = jobRepository.createJobInstance("foo", jobParameters);
+		JobExecution jobExecution = jobRepository.createJobExecution(jobInstance, jobParameters,
+				new ExecutionContext());
+
+		StepSupport stepA = new StepSupport("stepA") {
+			@Override
+			public void execute(StepExecution stepExecution) throws UnexpectedJobExecutionException {
+				stepExecution.setExitStatus(ExitStatus.FAILED);
+			}
+		};
+
+		StepSupport stepB = new StepSupport("stepB") {
+			@Override
+			public void execute(StepExecution stepExecution) throws UnexpectedJobExecutionException {
+			}
+		};
+
+		StepSupport stepC = new StepSupport("stepC") {
+			@Override
+			public void execute(StepExecution stepExecution) throws UnexpectedJobExecutionException {
+			}
+		};
+
+		FlowExecution flowExecution = builder.start(stepA)
+			.on("*")
+			.to(stepB)
+			.from(stepA)
+			.on(ExitStatus.FAILED)
+			.to(stepC)
+			.end()
+			.start(new JobFlowExecutor(jobRepository, new SimpleStepHandler(jobRepository), jobExecution));
+
+		Iterator<StepExecution> stepExecutions = jobExecution.getStepExecutions().iterator();
+		assertEquals("stepA", stepExecutions.next().getStepName());
+		assertEquals("stepC", stepExecutions.next().getStepName());
+		assertFalse(stepExecutions.hasNext());
+	}
+
 	private static StepSupport createCompleteStep(String name) {
 		return new StepSupport(name) {
 			@Override

spring-batch-core/src/test/java/org/springframework/batch/core/job/builder/FlowJobBuilderTests.java

@@ -171,6 +171,18 @@ void testBuildOverTwoLines() throws JobInterruptedException {
 		assertEquals(2, execution.getStepExecutions().size());
 	}
 
+	@Test
+	void testBuildOnExitStatus() throws JobInterruptedException {
+		FlowJobBuilder builder = new JobBuilder("flow", jobRepository).start(step1)
+			.on(ExitStatus.COMPLETED)
+			.to(step2)
+			.end();
+		builder.preventRestart();
+		builder.build().execute(execution);
+		assertEquals(BatchStatus.COMPLETED, execution.getStatus());
+		assertEquals(2, execution.getStepExecutions().size());
+	}
+
 	@Test
 	void testBuildSubflow() throws JobInterruptedException {
 		Flow flow = new FlowBuilder<Flow>("subflow").from(step1).end();
@@ -278,6 +290,24 @@ public FlowExecutionStatus decide(JobExecution jobExecution, @Nullable StepExecu
 		assertEquals(1, execution.getStepExecutions().size());
 	}
 
+	@Test
+	void testBuildWithDeciderAtStartOnExitStatus() throws JobInterruptedException {
+		JobExecutionDecider decider = new JobExecutionDecider() {
+			private int count = 0;
+
+			@Override
+			public FlowExecutionStatus decide(JobExecution jobExecution, @Nullable StepExecution stepExecution) {
+				count++;
+				return count < 2 ? new FlowExecutionStatus("ONGOING") : FlowExecutionStatus.COMPLETED;
+			}
+		};
+		JobFlowBuilder builder = new JobBuilder("flow", jobRepository).start(decider);
+		builder.on(ExitStatus.COMPLETED).end().from(decider).on("*").to(step1).end();
+		builder.build().preventRestart().build().execute(execution);
+		assertEquals(BatchStatus.COMPLETED, execution.getStatus());
+		assertEquals(1, execution.getStepExecutions().size());
+	}
+
 	@Test
 	void testBuildWithDeciderPriorityOnWildcardCount() throws JobInterruptedException {
 		JobExecutionDecider decider = (jobExecution, stepExecution) -> new FlowExecutionStatus("COMPLETED_PARTIALLY");