Fix/null pointer exception parallel remove map step registry

pom.xml

@@ -127,6 +127,7 @@
 		<jruby.version>9.4.13.0</jruby.version>
 		<lettuce.version>6.8.0.RELEASE</lettuce.version>
 		<jedis.version>6.1.0</jedis.version>
+		<vmlens.version>1.2.14</vmlens.version>
 
 		<!-- samples dependencies -->
 		<spring-rabbit.version>${spring-amqp.version}</spring-rabbit.version>

spring-batch-core/pom.xml

@@ -402,6 +402,12 @@
 				</exclusion>
 			</exclusions>
 		</dependency>
+		<dependency>
+			<groupId>com.vmlens</groupId>
+			<artifactId>api</artifactId>
+			<version>${vmlens.version}</version>
+			<scope>test</scope>
+		</dependency>
 
 		<!-- provided dependencies -->
 		<dependency>
@@ -412,4 +418,27 @@
 		</dependency>
 	</dependencies>
 
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>com.vmlens</groupId>
+				<artifactId>vmlens-maven-plugin</artifactId>
+				<version>${vmlens.version}</version>
+				<executions>
+					<execution>
+						<id>test</id>
+						<goals>
+							<goal>test</goal>
+						</goals>
+					</execution>
+				</executions>
+				<configuration>
+					<includes>
+						<include>**/*CT.java</include>
+					</includes>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+
 </project>

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/MapStepRegistry.java

@@ -65,11 +65,11 @@ public void unregisterStepsFromJob(String jobName) {
 	public Step getStep(String jobName, String stepName) throws NoSuchJobException {
 		Assert.notNull(jobName, "The job name cannot be null.");
 		Assert.notNull(stepName, "The step name cannot be null.");
-		if (!map.containsKey(jobName)) {
+		final Map<String, Step> jobSteps = map.get(jobName);
+		if (jobSteps == null) {
 			throw new NoSuchJobException("No job configuration with the name [" + jobName + "] was registered");
 		}
 		else {
-			final Map<String, Step> jobSteps = map.get(jobName);
 			if (jobSteps.containsKey(stepName)) {
 				return jobSteps.get(stepName);
 			}

spring-batch-core/src/test/java/org/springframework/batch/core/configuration/support/MapStepRegistryCT.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2006-2023 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.configuration.support;
+
+import com.vmlens.api.AllInterleavings;
+import org.junit.jupiter.api.Test;
+import org.springframework.batch.core.configuration.DuplicateJobException;
+import org.springframework.batch.core.configuration.StepRegistry;
+import org.springframework.batch.core.launch.NoSuchJobException;
+import org.springframework.batch.core.step.tasklet.TaskletStep;
+
+import java.util.List;
+
+/**
+ * @author Thomas Krieger
+ */
+public class MapStepRegistryCT {
+
+	@Test
+	public void unregisterAndGet() throws DuplicateJobException, InterruptedException {
+		try (AllInterleavings allInterleavings = new AllInterleavings("MapStepRegistryCT.unregisterAndGet")) {
+			while (allInterleavings.hasNext()) {
+				StepRegistry registry = new MapStepRegistry();
+				registry.register("foo", List.of(new TaskletStep("first")));
+				Thread first = new Thread() {
+					@Override
+					public void run() {
+						registry.unregisterStepsFromJob("foo");
+					}
+				};
+				first.start();
+				try {
+					registry.getStep("foo", "first");
+				}
+				catch (NoSuchJobException e) {
+
+				}
+				first.join();
+			}
+		}
+	}
+
+}