OPEN - BATCH-803: Add non-buffering ChunkOrientedTasklet (or option in existing one) plus flag for factory bean

added SimpleChunkOrientedTasklet *not* designed for inheritance, so that we can deal with fault-tolerance concerns separately and in one place

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

@@ -0,0 +1,79 @@
+package org.springframework.batch.core.step.item;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.springframework.batch.core.StepContribution;
+import org.springframework.batch.core.step.tasklet.Tasklet;
+import org.springframework.batch.item.ItemProcessor;
+import org.springframework.batch.item.ItemReader;
+import org.springframework.batch.item.ItemWriter;
+import org.springframework.batch.repeat.ExitStatus;
+import org.springframework.batch.repeat.RepeatCallback;
+import org.springframework.batch.repeat.RepeatContext;
+import org.springframework.batch.repeat.RepeatOperations;
+import org.springframework.core.AttributeAccessor;
+
+/**
+ * Simplest possible implementation of {@link Tasklet} with no skipping or
+ * recovering. Just delegates all calls to the provided {@link ItemReader} and
+ * {@link ItemWriter}.
+ * 
+ * @author Dave Syer
+ * @author Robert Kasanicky
+ */
+public class SimpleChunkOrientedTasklet<I, O> extends AbstractItemProcessingTasklet<I, O> {
+
+	private RepeatOperations repeatOperations;
+
+	public SimpleChunkOrientedTasklet(ItemReader<? extends I> itemReader,
+			ItemProcessor<? super I, ? extends O> itemProcessor, ItemWriter<? super O> itemWriter,
+			RepeatOperations repeatOperations) {
+		super(itemReader, itemProcessor, itemWriter);
+		this.repeatOperations = repeatOperations;
+	}
+
+	/**
+	 * Read-process-write a list of items.
+	 */
+	public ExitStatus execute(final StepContribution contribution, AttributeAccessor attributes) throws Exception {
+		ExitStatus result = ExitStatus.CONTINUABLE;
+		final List<I> inputs = new ArrayList<I>();
+
+		result = repeatOperations.iterate(new RepeatCallback() {
+
+			public ExitStatus doInIteration(final RepeatContext context) throws Exception {
+				I item = doRead();
+
+				if (item == null) {
+					return ExitStatus.FINISHED;
+				}
+				inputs.add(item);
+				contribution.incrementReadCount();
+				return ExitStatus.CONTINUABLE;
+			}
+		});
+
+		// If there is no input we don't have to do anything more
+		if (inputs.isEmpty()) {
+			return result;
+		}
+
+		List<O> outputs = new ArrayList<O>();
+		for (I item : inputs) {
+			O output = doProcess(item);
+			if (output != null) {
+				outputs.add(output);
+			}
+		}
+		contribution.incrementFilterCount(inputs.size() - outputs.size());
+		
+		// TODO: use ItemWriter interface properly
+		// TODO: make sure exceptions get handled by the appropriate handler
+		doWrite(outputs);
+		contribution.incrementWriteCount(outputs.size());
+
+		return result;
+	}
+
+}

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

@@ -457,7 +457,7 @@ public class SimpleStepFactoryBean<T,S> implements FactoryBean, BeanNameAware {
 
 		step.setStepOperations(stepOperations);
 
-		ChunkOrientedTasklet<T,S> tasklet = new ChunkOrientedTasklet<T,S>(itemReader, itemProcessor, itemWriter, chunkOperations);
+		SimpleChunkOrientedTasklet<T,S> tasklet = new SimpleChunkOrientedTasklet<T,S>(itemReader, itemProcessor, itemWriter, chunkOperations);
 		tasklet.setListeners(getListeners());
 		step.setTasklet(tasklet);