Refine ChunkOrientedStepBuilder to fix generics

Closes GH-5358

Signed-off-by: Yanming Zhou <zhouyanming@gmail.com>

Author: quaff

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

@@ -71,17 +71,18 @@
  * to provide common properties and methods for building chunk-oriented steps.
  *
  * @author Mahmoud Ben Hassine
+ * @author Yanming Zhou
  * @since 6.0
  */
 public class ChunkOrientedStepBuilder<I, O> extends StepBuilderHelper<ChunkOrientedStepBuilder<I, O>> {
 
 	private final int chunkSize;
 
-	private @Nullable ItemReader<I> reader;
+	private @Nullable ItemReader<? extends I> reader;
 
-	private @Nullable ItemProcessor<I, O> processor;
+	private @Nullable ItemProcessor<? super I, ? extends O> processor;
 
-	private @Nullable ItemWriter<O> writer;
+	private @Nullable ItemWriter<? super O> writer;
 
 	private PlatformTransactionManager transactionManager = new ResourcelessTransactionManager();
 
@@ -155,7 +156,7 @@ protected ChunkOrientedStepBuilder<I, O> self() {
 	 * @param reader an item reader
 	 * @return this for fluent chaining
 	 */
-	public ChunkOrientedStepBuilder<I, O> reader(ItemReader<I> reader) {
+	public ChunkOrientedStepBuilder<I, O> reader(ItemReader<? extends I> reader) {
 		this.reader = reader;
 		return self();
 	}
@@ -167,7 +168,7 @@ public ChunkOrientedStepBuilder<I, O> reader(ItemReader<I> reader) {
 	 * @param processor an item processor
 	 * @return this for fluent chaining
 	 */
-	public ChunkOrientedStepBuilder<I, O> processor(ItemProcessor<I, O> processor) {
+	public ChunkOrientedStepBuilder<I, O> processor(ItemProcessor<? super I, ? extends O> processor) {
 		this.processor = processor;
 		return self();
 	}
@@ -179,7 +180,7 @@ public ChunkOrientedStepBuilder<I, O> processor(ItemProcessor<I, O> processor) {
 	 * @param writer an item writer
 	 * @return this for fluent chaining
 	 */
-	public ChunkOrientedStepBuilder<I, O> writer(ItemWriter<O> writer) {
+	public ChunkOrientedStepBuilder<I, O> writer(ItemWriter<? super O> writer) {
 		this.writer = writer;
 		return self();
 	}
@@ -395,7 +396,6 @@ public ChunkOrientedStepBuilder<I, O> observationRegistry(ObservationRegistry ob
 		return self();
 	}
 
-	@SuppressWarnings("unchecked")
 	public ChunkOrientedStep<I, O> build() {
 		Assert.notNull(this.reader, "Item reader must not be null");
 		Assert.notNull(this.writer, "Item writer must not be null");
@@ -457,6 +457,7 @@ public ChunkOrientedStep<I, O> build() {
 		return chunkOrientedStep;
 	}
 
+	@SuppressWarnings({ "rawtypes", "unchecked" })
 	private void registerTypedListener(StepListener stepListener, ChunkOrientedStep<I, O> chunkOrientedStep) {
 		if (stepListener instanceof ItemReadListener listener) {
 			chunkOrientedStep.registerItemReadListener(listener);

spring-batch-core/src/main/java/org/springframework/batch/core/step/item/ChunkOrientedStep.java

@@ -91,6 +91,7 @@
  * @author Andrey Litvitski
  * @author xeounxzxu
  * @author Minchul Son
+ * @author Yanming Zhou
  * @since 6.0
  */
 public class ChunkOrientedStep<I, O> extends AbstractStep {
@@ -100,16 +101,16 @@ public class ChunkOrientedStep<I, O> extends AbstractStep {
 	/*
 	 * Step Input / Output parameters
 	 */
-	private final ItemReader<I> itemReader;
+	private final ItemReader<? extends I> itemReader;
 
 	private final CompositeItemReadListener<I> compositeItemReadListener = new CompositeItemReadListener<>();
 
 	@SuppressWarnings("unchecked")
-	private ItemProcessor<I, O> itemProcessor = item -> (O) item;
+	private ItemProcessor<? super I, ? extends O> itemProcessor = item -> (O) item;
 
 	private final CompositeItemProcessListener<I, O> compositeItemProcessListener = new CompositeItemProcessListener<>();
 
-	private final ItemWriter<O> itemWriter;
+	private final ItemWriter<? super O> itemWriter;
 
 	private final CompositeItemWriteListener<O> compositeItemWriteListener = new CompositeItemWriteListener<>();
 
@@ -168,8 +169,8 @@ public class ChunkOrientedStep<I, O> extends AbstractStep {
 	 * @param itemWriter the item writer to write items
 	 * @param jobRepository the job repository to use for this step
 	 */
-	public ChunkOrientedStep(String name, int chunkSize, ItemReader<I> itemReader, ItemWriter<O> itemWriter,
-			JobRepository jobRepository) {
+	public ChunkOrientedStep(String name, int chunkSize, ItemReader<? extends I> itemReader,
+			ItemWriter<? super O> itemWriter, JobRepository jobRepository) {
 		super(jobRepository);
 		this.chunkSize = chunkSize;
 		this.itemReader = itemReader;
@@ -181,7 +182,7 @@ public ChunkOrientedStep(String name, int chunkSize, ItemReader<I> itemReader, I
 	 * Set the item processor to use for processing items.
 	 * @param itemProcessor the item processor to set
 	 */
-	public void setItemProcessor(ItemProcessor<I, O> itemProcessor) {
+	public void setItemProcessor(ItemProcessor<? super I, ? extends O> itemProcessor) {
 		Assert.notNull(itemProcessor, "Item processor must not be null");
 		this.itemProcessor = itemProcessor;
 	}