Fix listener API allowing invalid listeners

Before listeners could be created without annotations which then would be ignored during runtime.
Now listeners without annotations will throw an IllegalArgumentException

Resolves #4808

Signed-off-by: Sacha Leemann <sacha.leemann@yahoo.de>

Author: SoxerL

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

@@ -161,6 +161,9 @@ public B listener(Object listener) {
 			factory.setDelegate(listener);
 			properties.addJobExecutionListener((JobExecutionListener) factory.getObject());
 		}
+		else {
+			throw new IllegalArgumentException("Missing @BeforeJob or @AfterJob annotations on Listener.");
+		}
 
 		@SuppressWarnings("unchecked")
 		B result = (B) this;

spring-batch-core/src/main/java/org/springframework/batch/core/step/builder/StepBuilderHelper.java

@@ -125,6 +125,9 @@ public B listener(Object listener) {
 			factory.setDelegate(listener);
 			properties.addStepExecutionListener((StepExecutionListener) factory.getObject());
 		}
+		else {
+			throw new IllegalArgumentException("Missing @BeforeStep or @AfterStep annotations on Listener.");
+		}
 
 		return self();
 	}

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

@@ -19,6 +19,7 @@
 
 import org.junit.jupiter.api.Test;
 
+import org.mockito.Mockito;
 import org.springframework.batch.core.ExitStatus;
 import org.springframework.batch.core.job.Job;
 import org.springframework.batch.core.job.JobExecution;
@@ -40,6 +41,7 @@
 import org.springframework.transaction.PlatformTransactionManager;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 /**
  * @author Mahmoud Ben Hassine
@@ -65,6 +67,16 @@ void testListeners() throws Exception {
 
 	}
 
+	@Test
+	void testInvalidListener() {
+		assertThrows(IllegalArgumentException.class,
+				() -> new JobBuilder("job", Mockito.mock()).listener(new InvalidListener())
+					.start(new StepBuilder("step", Mockito.mock())
+						.tasklet((contribution, chunkContext) -> RepeatStatus.FINISHED, Mockito.mock())
+						.build())
+					.build());
+	}
+
 	@Configuration
 	@EnableBatchProcessing
 	static class MyJobConfiguration {
@@ -130,4 +142,14 @@ public void afterJob(JobExecution jobExecution) {
 
 	}
 
+	public static class InvalidListener {
+
+		public void beforeStep() {
+		}
+
+		public void afterStep() {
+		}
+
+	}
+
 }

spring-batch-core/src/test/java/org/springframework/batch/core/step/builder/StepBuilderTests.java

@@ -60,6 +60,7 @@
 import org.springframework.transaction.PlatformTransactionManager;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 /**
  * @author Dave Syer
@@ -117,6 +118,13 @@ void testListeners() throws Exception {
 		assertEquals(1, AnnotationBasedStepExecutionListener.afterChunkCount);
 	}
 
+	@Test
+	void testMissingAnnotationsForListeners() {
+		assertThrows(IllegalArgumentException.class,
+				() -> new StepBuilder("step", jobRepository).listener(new InvalidListener())
+					.tasklet((contribution, chunkContext) -> null, transactionManager));
+	}
+
 	@Test
 	void testAnnotationBasedChunkListenerForTaskletStep() throws Exception {
 		TaskletStepBuilder builder = new StepBuilder("step", jobRepository)
@@ -465,4 +473,14 @@ public void afterChunkError() {
 
 	}
 
+	public static class InvalidListener {
+
+		public void beforeStep() {
+		}
+
+		public void afterStep() {
+		}
+
+	}
+
 }