Step names must be unique #3757

pom.xml

@@ -152,6 +152,26 @@
 		<spring-javaformat-maven-plugin.version>0.0.39</spring-javaformat-maven-plugin.version>
 	</properties>
 
+	<dependencyManagement>
+		<dependencies>
+			<dependency>
+				<groupId>org.slf4j</groupId>
+				<artifactId>jcl-over-slf4j</artifactId>
+				<version>${slf4j.version}</version>
+			</dependency>
+			<dependency>
+				<groupId>org.slf4j</groupId>
+				<artifactId>slf4j-api</artifactId>
+				<version>${slf4j.version}</version>
+			</dependency>
+			<dependency>
+				<groupId>org.slf4j</groupId>
+				<artifactId>slf4j-simple</artifactId>
+				<version>${slf4j.version}</version>
+			</dependency>
+		</dependencies>
+	</dependencyManagement>
+
 	<build>
 		<plugins>
 			<plugin>

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,8 +17,7 @@
 package org.springframework.batch.core.job;
 
 import java.time.LocalDateTime;
-import java.util.Collection;
-import java.util.List;
+import java.util.*;
 import java.util.stream.Collectors;
 
 import io.micrometer.core.instrument.LongTaskTimer;
@@ -43,6 +42,7 @@
 import org.springframework.batch.core.StartLimitExceededException;
 import org.springframework.batch.core.Step;
 import org.springframework.batch.core.StepExecution;
+import org.springframework.batch.core.job.builder.AlreadyUsedStepNameException;
 import org.springframework.batch.core.launch.NoSuchJobException;
 import org.springframework.batch.core.launch.support.ExitCodeMapper;
 import org.springframework.batch.core.listener.CompositeJobExecutionListener;
@@ -300,6 +300,7 @@ public final void execute(JobExecution execution) {
 
 				execution.setStartTime(LocalDateTime.now());
 				updateStatus(execution, BatchStatus.STARTED);
+				checkStepNamesUnicity();
 
 				listener.beforeJob(execution);
 
@@ -368,11 +369,11 @@ public final void execute(JobExecution execution) {
 			finally {
 				JobSynchronizationManager.release();
 			}
-
 		}
-
 	}
 
+	protected abstract void checkStepNamesUnicity() throws AlreadyUsedStepNameException;
+
 	private void stopObservation(JobExecution execution, Observation observation) {
 		List<Throwable> throwables = execution.getFailureExceptions();
 		if (!throwables.isEmpty()) {
@@ -430,6 +431,16 @@ else if (ex instanceof NoSuchJobException || ex.getCause() instanceof NoSuchJobE
 		return exitStatus;
 	}
 
+	protected static void addToMapCheckingUnicity(Map<String, Step> map, Step step, String name)
+			throws AlreadyUsedStepNameException {
+		map.merge(name, step, (old, value) -> {
+			if (!old.equals(value)) {
+				throw new AlreadyUsedStepNameException(name);
+			}
+			return old;
+		});
+	}
+
 	private void updateStatus(JobExecution jobExecution, BatchStatus status) {
 		jobExecution.setStatus(status);
 		jobRepository.update(jobExecution);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,7 @@
 
 package org.springframework.batch.core.job;
 
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
+import java.util.*;
 
 import org.springframework.batch.core.BatchStatus;
 import org.springframework.batch.core.Job;
@@ -145,4 +143,9 @@ protected void doExecute(JobExecution execution)
 		}
 	}
 
+	@Override
+	protected void checkStepNamesUnicity() {
+		// noop : steps of SimpleJob can share the same name
+	}
+
 }

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

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2006-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.batch.core.job.builder;
+
+/**
+ * Exception to indicate the name of a step is already used by a different step in the
+ * same flow. Step names must be unique within a flow definition because the search of the
+ * next step to find relies on the step name
+ *
+ * @author Fabrice Bibonne
+ */
+public class AlreadyUsedStepNameException extends RuntimeException {
+
+	public AlreadyUsedStepNameException(String name) {
+		super("the name " + name + " is already used");
+	}
+
+}

spring-batch-core/src/main/java/org/springframework/batch/core/job/flow/FlowJob.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,19 +15,20 @@
  */
 package org.springframework.batch.core.job.flow;
 
-import java.util.Collection;
-import java.util.Map;
-import java.util.concurrent.ConcurrentHashMap;
-
 import org.springframework.batch.core.Job;
 import org.springframework.batch.core.JobExecution;
 import org.springframework.batch.core.JobExecutionException;
 import org.springframework.batch.core.Step;
 import org.springframework.batch.core.job.AbstractJob;
 import org.springframework.batch.core.job.SimpleStepHandler;
+import org.springframework.batch.core.job.builder.AlreadyUsedStepNameException;
 import org.springframework.batch.core.step.StepHolder;
 import org.springframework.batch.core.step.StepLocator;
 
+import java.util.Collection;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
 /**
  * Implementation of the {@link Job} interface that allows for complex flows of steps,
  * rather than requiring sequential execution. In general, this job implementation was
@@ -74,50 +75,50 @@ public void setFlow(Flow flow) {
 	 */
 	@Override
 	public Step getStep(String stepName) {
-		if (!initialized) {
-			init();
-		}
+		init();
 		return stepMap.get(stepName);
 	}
 
 	/**
 	 * Initialize the step names
 	 */
 	private void init() {
-		findSteps(flow, stepMap);
-		initialized = true;
+		if (!initialized) {
+			findStepsThrowingIfNameNotUnique(flow);
+			initialized = true;
+		}
 	}
 
-	private void findSteps(Flow flow, Map<String, Step> map) {
+	private void findStepsThrowingIfNameNotUnique(Flow flow) {
 
 		for (State state : flow.getStates()) {
 			if (state instanceof StepLocator locator) {
 				for (String name : locator.getStepNames()) {
-					map.put(name, locator.getStep(name));
+					addToMapCheckingUnicity(this.stepMap, locator.getStep(name), name);
 				}
 			}
-			else if (state instanceof StepHolder) {
-				Step step = ((StepHolder) state).getStep();
-				String name = step.getName();
-				stepMap.put(name, step);
+			// TODO remove this else bock ? not executed during tests : the only State
+			// which implements StepHolder is StepState which already implements
+			// StepLocator
+			// within tests coverage `state instanceof StepHolder` is false 30 times/30
+			else if (state instanceof StepHolder stepHolder) {
+				Step step = stepHolder.getStep();
+				addToMapCheckingUnicity(this.stepMap, step, step.getName());
 			}
-			else if (state instanceof FlowHolder) {
-				for (Flow subflow : ((FlowHolder) state).getFlows()) {
-					findSteps(subflow, map);
+			else if (state instanceof FlowHolder flowHolder) {
+				for (Flow subflow : flowHolder.getFlows()) {
+					findStepsThrowingIfNameNotUnique(subflow);
 				}
 			}
 		}
-
 	}
 
 	/**
 	 * {@inheritDoc}
 	 */
 	@Override
 	public Collection<String> getStepNames() {
-		if (!initialized) {
-			init();
-		}
+		init();
 		return stepMap.keySet();
 	}
 
@@ -139,4 +140,9 @@ protected void doExecute(final JobExecution execution) throws JobExecutionExcept
 		}
 	}
 
+	@Override
+	protected void checkStepNamesUnicity() throws AlreadyUsedStepNameException {
+		init();
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,31 +17,20 @@
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import org.springframework.batch.core.BatchStatus;
-import org.springframework.batch.core.JobExecution;
-import org.springframework.batch.core.JobExecutionException;
-import org.springframework.batch.core.JobInterruptedException;
-import org.springframework.batch.core.JobParameters;
-import org.springframework.batch.core.JobParametersInvalidException;
-import org.springframework.batch.core.Step;
-import org.springframework.batch.core.StepExecution;
+import org.springframework.batch.core.*;
 import org.springframework.batch.core.repository.JobRepository;
 import org.springframework.batch.core.repository.support.JobRepositoryFactoryBean;
 import org.springframework.batch.core.step.StepSupport;
-import org.springframework.jdbc.support.JdbcTransactionManager;
 import org.springframework.jdbc.datasource.embedded.EmbeddedDatabase;
 import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
+import org.springframework.jdbc.support.JdbcTransactionManager;
 import org.springframework.lang.Nullable;
 
 import java.time.LocalDateTime;
 import java.util.Collection;
 import java.util.Collections;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertNull;
-import static org.junit.jupiter.api.Assertions.assertThrows;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.*;
 
 /**
  * @author Dave Syer
@@ -215,6 +204,10 @@ public StubJob() {
 		protected void doExecute(JobExecution execution) throws JobExecutionException {
 		}
 
+		@Override
+		protected void checkStepNamesUnicity() {
+		}
+
 		@Override
 		public Step getStep(String stepName) {
 			return null;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -513,6 +513,25 @@ void testGetMultipleJobParameters() throws Exception {
 
 	}
 
+	@Test
+	public void testMultipleStepsWithSameName() {
+		job.setName("MultipleStepsWithSameName");
+		String sharedName = "stepName";
+		final List<String> executionsCallbacks = new ArrayList<>();
+		StubStep sharedNameStep1 = new StubStep(sharedName, jobRepository);
+		sharedNameStep1.setCallback(() -> executionsCallbacks.add("step1"));
+		job.addStep(sharedNameStep1);
+		StubStep sharedNameStep2 = new StubStep(sharedName, jobRepository);
+		sharedNameStep2.setCallback(() -> executionsCallbacks.add("step2"));
+		job.addStep(sharedNameStep2);
+		StubStep sharedNameStep3 = new StubStep(sharedName, jobRepository);
+		sharedNameStep3.setCallback(() -> executionsCallbacks.add("step3"));
+		job.addStep(sharedNameStep3);
+		job.execute(jobExecution);
+		assertEquals(List.of("step1", "step2", "step3"), executionsCallbacks);
+		assertEquals(BatchStatus.COMPLETED, jobExecution.getStatus());
+	}
+
 	/*
 	 * Check JobRepository to ensure status is being saved.
 	 */