Allow lambdas to be passed as item processors

Resolves #4061

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2021 the original author or authors.
+ * Copyright 2006-2022 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.
@@ -20,7 +20,6 @@
 import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.Set;
-import java.util.function.Function;
 
 import org.springframework.batch.core.ChunkListener;
 import org.springframework.batch.core.ItemProcessListener;
@@ -47,7 +46,6 @@
 import org.springframework.batch.item.ItemReader;
 import org.springframework.batch.item.ItemStream;
 import org.springframework.batch.item.ItemWriter;
-import org.springframework.batch.item.function.FunctionItemProcessor;
 import org.springframework.batch.repeat.CompletionPolicy;
 import org.springframework.batch.repeat.RepeatOperations;
 import org.springframework.batch.repeat.policy.SimpleCompletionPolicy;
@@ -78,8 +76,6 @@ public class SimpleStepBuilder<I, O> extends AbstractTaskletStepBuilder<SimpleSt
 
 	private ItemProcessor<? super I, ? extends O> processor;
 
-	private Function<? super I, ? extends O> itemProcessorFunction;
-
 	private int chunkSize = 0;
 
 	private RepeatOperations chunkOperations;
@@ -112,7 +108,6 @@ protected SimpleStepBuilder(SimpleStepBuilder<I, O> parent) {
 		this.reader = parent.reader;
 		this.writer = parent.writer;
 		this.processor = parent.processor;
-		this.itemProcessorFunction = parent.itemProcessorFunction;
 		this.itemListeners = parent.itemListeners;
 		this.readerTransactionalQueue = parent.readerTransactionalQueue;
 	}
@@ -236,19 +231,6 @@ public SimpleStepBuilder<I, O> processor(ItemProcessor<? super I, ? extends O> p
 		return this;
 	}
 
-	/**
-	 * A {@link Function} to be delegated to as an {@link ItemProcessor}.  If this is set,
-	 * it will take precedence over any {@code ItemProcessor} configured via
-	 * {@link #processor(ItemProcessor)}.
-	 *
-	 * @param function the function to delegate item processing to
-	 * @return this for fluent chaining
-	 */
-	public SimpleStepBuilder<I, O> processor(Function<? super I, ? extends O> function) {
-		this.itemProcessorFunction = function;
-		return this;
-	}
-
 	/**
 	 * Sets a flag to say that the reader is transactional (usually a queue), which is to say that failed items might be
 	 * rolled back and re-presented in a subsequent transaction. Default is false, meaning that the items are read
@@ -359,10 +341,6 @@ protected ItemWriter<? super O> getWriter() {
 	}
 
 	protected ItemProcessor<? super I, ? extends O> getProcessor() {
-		if(this.itemProcessorFunction != null) {
-			this.processor = new FunctionItemProcessor<>(this.itemProcessorFunction);
-		}
-
 		return processor;
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -17,7 +17,6 @@
 
 import java.util.Arrays;
 import java.util.List;
-import java.util.function.Function;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -245,7 +244,7 @@ private void assertStepFunctions(boolean faultTolerantStep) throws Exception {
 				.transactionManager(transactionManager)
 				.<Object, String>chunk(3)
 				.reader(reader)
-				.processor((Function<Object, String>) s -> s.toString())
+				.processor(Object::toString)
 				.writer(itemWriter)
 				.listener(new AnnotationBasedStepExecutionListener());
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2021 the original author or authors.
+ * Copyright 2010-2022 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.
@@ -70,7 +70,6 @@ public class FaultTolerantStepIntegrationTests {
 	@Before
 	public void setUp() {
 		ItemReader<Integer> itemReader = new ListItemReader<>(createItems());
-		ItemProcessor<Integer, Integer> itemProcessor = item -> item > 20 ? null : item;
 		ItemWriter<Integer> itemWriter = chunk -> {
 			if (chunk.contains(1)) {
 				throw new IllegalArgumentException();
@@ -80,7 +79,7 @@ public void setUp() {
 		stepBuilder = new StepBuilderFactory(jobRepository, transactionManager).get("step")
 				.<Integer, Integer>chunk(CHUNK_SIZE)
 				.reader(itemReader)
-				.processor(itemProcessor)
+				.processor(item -> item > 20 ? null : item)
 				.writer(itemWriter)
 				.faultTolerant();
 	}