FEATURE: validate step listeners

spring-batch-core/src/main/java/org/springframework/batch/core/listener/StepListenerFactoryBean.java

@@ -15,6 +15,9 @@
  */
 package org.springframework.batch.core.listener;
 
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
 import org.springframework.batch.core.StepListener;
 
 /**
@@ -23,11 +26,22 @@
  *
  * @author Lucas Ward
  * @author Dan Garrette
+ * @author Alexei KLENIN
  * @since 2.0
  * @see AbstractListenerFactoryBean
  * @see StepListenerMetaData
  */
 public class StepListenerFactoryBean extends AbstractListenerFactoryBean<StepListener> {
+	private static final String STR_STEP_LISTENER_ANNOTATIONS_LIST = Stream
+			.of(StepListenerMetaData.values())
+			.map(StepListenerMetaData::getAnnotation)
+			.map(Class::getSimpleName)
+			.map(annotation -> String.format("\t- @%s\n", annotation))
+			.collect(Collectors.joining());
+	private static final String ERR_OBJECT_NOT_STEP_LISTENER_TEMPLATE =
+			"Object of type [%s] is not a valid step listener. " +
+			"It must ether implement StepListener interface or have methods annotated with any of:\n" +
+			STR_STEP_LISTENER_ANNOTATIONS_LIST;
 
 	@Override
 	protected ListenerMetaData getMetaDataFromPropertyName(String propertyName) {
@@ -74,4 +88,19 @@ public static StepListener getListener(Object delegate) {
 	public static boolean isListener(Object delegate) {
 		return AbstractListenerFactoryBean.isListener(delegate, StepListener.class, StepListenerMetaData.values());
 	}
+
+	/**
+	 * Asserts that {@code delegate} is a valid step listener. If this is not a case, throws an
+	 * {@link IllegalArgumentException} with message detailing the problem. Object is a valid
+	 * step listener is it ether implements interface {@link StepListener} or has any method
+	 * annotated with one of marker annotations.
+	 *
+	 * @param delegate the object to check
+	 */
+	public static void assertListener(Object delegate) {
+		if (!isListener(delegate)) {
+			throw new IllegalArgumentException(String.format(
+					ERR_OBJECT_NOT_STEP_LISTENER_TEMPLATE, delegate.getClass().getName()));
+		}
+	}
 }

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

@@ -23,6 +23,7 @@
 import org.springframework.batch.core.ChunkListener;
 import org.springframework.batch.core.Step;
 import org.springframework.batch.core.StepExecutionListener;
+import org.springframework.batch.core.StepListener;
 import org.springframework.batch.core.annotation.AfterChunk;
 import org.springframework.batch.core.annotation.AfterChunkError;
 import org.springframework.batch.core.annotation.BeforeChunk;
@@ -47,6 +48,7 @@
  * @author Dave Syer
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
+ * @author Alexei Klenin
  *
  * @since 2.2
  *
@@ -159,10 +161,9 @@ public B listener(Object listener) {
 		chunkListenerMethods.addAll(ReflectionUtils.findMethod(listener.getClass(), AfterChunk.class));
 		chunkListenerMethods.addAll(ReflectionUtils.findMethod(listener.getClass(), AfterChunkError.class));
 
-		if(chunkListenerMethods.size() > 0) {
-			StepListenerFactoryBean factory = new StepListenerFactoryBean();
-			factory.setDelegate(listener);
-			this.listener((ChunkListener) factory.getObject());
+		if (!chunkListenerMethods.isEmpty()) {
+			StepListener stepListener = StepListenerFactoryBean.getListener(listener);
+			this.listener((ChunkListener) stepListener);
 		}
 
 		@SuppressWarnings("unchecked")

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

@@ -91,6 +91,7 @@
  * @author Chris Schaefer
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
+ * @author Alexei Klenin
  *
  * @since 2.2
  */
@@ -204,18 +205,14 @@ public SimpleStepBuilder<I, O> listener(Object listener) {
 		skipListenerMethods.addAll(ReflectionUtils.findMethod(listener.getClass(), OnSkipInProcess.class));
 		skipListenerMethods.addAll(ReflectionUtils.findMethod(listener.getClass(), OnSkipInWrite.class));
 
-		if(skipListenerMethods.size() > 0) {
-			StepListenerFactoryBean factory = new StepListenerFactoryBean();
-			factory.setDelegate(listener);
-			skipListeners.add((SkipListener) factory.getObject());
+		if (!skipListenerMethods.isEmpty()) {
+			StepListener stepListener = StepListenerFactoryBean.getListener(listener);
+			skipListeners.add((SkipListener<I, O>) stepListener);
 		}
 
-		@SuppressWarnings("unchecked")
-		SimpleStepBuilder<I, O> result = this;
-		return result;
+		return this;
 	}
 
-
 	/**
 	 * Register a skip listener.
 	 *

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

@@ -64,6 +64,7 @@
  *
  * @author Dave Syer
  * @author Mahmoud Ben Hassine
+ * @author Alexei Klenin
  *
  * @since 2.2
  */
@@ -265,7 +266,6 @@ public SimpleStepBuilder<I, O> readerIsTransactionalQueue() {
 	 * @param listener the object that has a method configured with listener annotation
 	 * @return this for fluent chaining
 	 */
-	@SuppressWarnings("unchecked")
 	@Override
 	public SimpleStepBuilder<I, O> listener(Object listener) {
 		super.listener(listener);
@@ -281,18 +281,14 @@ public SimpleStepBuilder<I, O> listener(Object listener) {
 		itemListenerMethods.addAll(ReflectionUtils.findMethod(listener.getClass(), OnProcessError.class));
 		itemListenerMethods.addAll(ReflectionUtils.findMethod(listener.getClass(), OnWriteError.class));
 
-		if(itemListenerMethods.size() > 0) {
-			StepListenerFactoryBean factory = new StepListenerFactoryBean();
-			factory.setDelegate(listener);
-			itemListeners.add((StepListener) factory.getObject());
+		if (!itemListenerMethods.isEmpty()) {
+			StepListener stepListener = StepListenerFactoryBean.getListener(listener);
+			itemListeners.add(stepListener);
 		}
 
-		@SuppressWarnings("unchecked")
-		SimpleStepBuilder<I, O> result = this;
-		return result;
+		return this;
 	}
 
-
 	/**
 	 * Register an item reader listener.
 	 *

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

@@ -17,8 +17,10 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+
 import org.springframework.batch.core.Step;
 import org.springframework.batch.core.StepExecutionListener;
+import org.springframework.batch.core.StepListener;
 import org.springframework.batch.core.annotation.AfterStep;
 import org.springframework.batch.core.annotation.BeforeStep;
 import org.springframework.batch.core.listener.StepListenerFactoryBean;
@@ -40,6 +42,7 @@
  * 
  * @author Dave Syer
  * @author Michael Minella
+ * @author Alexei Klenin
  *
  * @since 2.2
  */
@@ -91,14 +94,15 @@ public B startLimit(int startLimit) {
 	 * @return this for fluent chaining
 	 */
 	public B listener(Object listener) {
+		StepListenerFactoryBean.assertListener(listener);
+
 		Set<Method> stepExecutionListenerMethods = new HashSet<>();
 		stepExecutionListenerMethods.addAll(ReflectionUtils.findMethod(listener.getClass(), BeforeStep.class));
 		stepExecutionListenerMethods.addAll(ReflectionUtils.findMethod(listener.getClass(), AfterStep.class));
 
-		if(stepExecutionListenerMethods.size() > 0) {
-			StepListenerFactoryBean factory = new StepListenerFactoryBean();
-			factory.setDelegate(listener);
-			properties.addStepExecutionListener((StepExecutionListener) factory.getObject());
+		if (!stepExecutionListenerMethods.isEmpty()) {
+			StepListener stepListener = StepListenerFactoryBean.getListener(listener);
+			properties.addStepExecutionListener((StepExecutionListener) stepListener);
 		}
 
 		@SuppressWarnings("unchecked")