Introduce KeyedItemReader to push the getKey() method into a separate place.

spring-batch-infrastructure/src/main/java/org/springframework/batch/io/cursor/JdbcCursorItemReader.java

@@ -31,7 +31,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.batch.io.Skippable;
 import org.springframework.batch.io.support.AbstractTransactionalIoSource;
-import org.springframework.batch.item.ItemReader;
+import org.springframework.batch.item.KeyedItemReader;
 import org.springframework.batch.item.ResourceLifecycle;
 import org.springframework.batch.restart.GenericRestartData;
 import org.springframework.batch.restart.RestartData;
@@ -117,7 +117,7 @@ import org.springframework.util.StringUtils;
  * @author Peter Zozom
  */
 public class JdbcCursorItemReader extends AbstractTransactionalIoSource
-		implements ItemReader, ResourceLifecycle, DisposableBean,
+		implements KeyedItemReader, ResourceLifecycle, DisposableBean,
 		InitializingBean, Restartable, StatisticsProvider, Skippable {
 
 	private static Log log = LogFactory.getLog(JdbcCursorItemReader.class);

spring-batch-infrastructure/src/main/java/org/springframework/batch/io/driving/DrivingQueryItemReader.java

@@ -19,7 +19,7 @@ import java.util.Iterator;
 import java.util.List;
 
 import org.springframework.batch.io.support.AbstractTransactionalIoSource;
-import org.springframework.batch.item.ItemReader;
+import org.springframework.batch.item.KeyedItemReader;
 import org.springframework.batch.item.ResourceLifecycle;
 import org.springframework.batch.repeat.synch.BatchTransactionSynchronizationManager;
 import org.springframework.batch.restart.RestartData;
@@ -51,7 +51,7 @@ import org.springframework.util.Assert;
  * @since 1.0
  */
 public class DrivingQueryItemReader extends AbstractTransactionalIoSource
-		implements ItemReader, ResourceLifecycle, InitializingBean,
+		implements KeyedItemReader, ResourceLifecycle, InitializingBean,
 		DisposableBean, Restartable {
 
 	private boolean initialized = false;

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/ItemReader.java

@@ -16,9 +16,10 @@
 
 package org.springframework.batch.item;
 
+import org.springframework.batch.item.reader.AbstractItemReader;
+
 /**
- * Strategy interface for providing the data for a given batch stage execution.
- * <br/>
+ * Strategy interface for providing the data. <br/>
  * 
  * Implementations are expected to be stateful and will be called multiple times
  * for each batch, with each call to {@link #next} returning a different value
@@ -26,8 +27,8 @@ package org.springframework.batch.item;
  * 
  * Implementations need to be thread safe and clients of a {@link ItemReader}
  * need to be aware that this is the case. Clients can code to this interface
- * without worrying about thread safety by using the AbstractItemProvider base
- * class.<br/>
+ * without worrying about thread safety by using the {@link AbstractItemReader}
+ * base class.<br/>
  * 
  * A richer interface (e.g. with a look ahead or peek) is not feasible because
  * we need to support transactions in an asynchronous batch.
@@ -50,15 +51,6 @@ public interface ItemReader {
 	 */
 	Object read() throws Exception;
 
-	/**
-	 * Get a unique identifier for the item that can be used to cache it between
-	 * calls if necessary, and then identify it later.
-	 * 
-	 * @param item the current item.
-	 * @return a unique identifier.
-	 */
-	Object getKey(Object item);
-	
 	/**
 	 * Close the reader, freeing any resources that may have been allocated
 	 * since the first call to read().

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/KeyedItemReader.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2006-2007 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.batch.item;
+
+/**
+ * Extension of the {@link ItemReader} interface that allows items to be
+ * identified and tagged by a unique key.
+ * 
+ * @author Dave Syer
+ * 
+ */
+public interface KeyedItemReader extends ItemReader {
+
+	/**
+	 * Get a unique identifier for the item that can be used to cache it between
+	 * calls if necessary, and then identify it later.
+	 * 
+	 * @param item the current item.
+	 * @return a unique identifier.
+	 */
+	Object getKey(Object item);
+
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/reader/AbstractItemReader.java

@@ -24,18 +24,11 @@ import org.springframework.batch.item.ItemReader;
  *
  */
 public abstract class AbstractItemReader implements ItemReader {
-
-	/**
-	 * Simply returns the item itself. Will be adequate for many purposes, but
-	 * not (for example) if the item is a message - in which case the identifier
-	 * should be used.
-	 * 
-	 * @see org.springframework.batch.item.ItemReader#getKey(java.lang.Object)
-	 */
-	public Object getKey(Object item) {
-		return item;
-	}
 	
+	/**
+	 * Do nothing.
+	 * @see org.springframework.batch.item.ItemReader#close()
+	 */
 	public void close() throws Exception {		
 	}
 

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/reader/ItemReaderAdapter.java

@@ -33,11 +33,11 @@ public class ItemReaderAdapter extends AbstractMethodInvokingDelegator implement
 		return invokeDelegateMethod();
     }
 
-    //harmless implementation of method required by ItemReader interface
-	public Object getKey(Object item) {
-		return item;
-	}
-
+	/**
+	 * Do nothing.
+	 * 
+	 * @see org.springframework.batch.item.ItemReader#close()
+	 */
 	public void close() throws Exception {
 		
 	}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/reader/JmsItemReader.java

@@ -24,6 +24,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.batch.item.FailedItemIdentifier;
 import org.springframework.batch.item.ItemReader;
+import org.springframework.batch.item.KeyedItemReader;
 import org.springframework.batch.item.exception.UnexpectedInputException;
 import org.springframework.jms.JmsException;
 import org.springframework.jms.core.JmsOperations;
@@ -39,7 +40,7 @@ import org.springframework.util.Assert;
  * @author Dave Syer
  * 
  */
-public class JmsItemReader extends AbstractItemReader implements FailedItemIdentifier {
+public class JmsItemReader extends AbstractItemReader implements KeyedItemReader, FailedItemIdentifier {
 
 	protected Log logger = LogFactory.getLog(getClass());
 
@@ -151,7 +152,7 @@ public class JmsItemReader extends AbstractItemReader implements FailedItemIdent
 				throw new UnexpectedInputException("Could not extract message ID", e);
 			}
 		}
-		return super.getKey(item);
+		return item;
 	}
 
 	/**

spring-batch-infrastructure/src/main/java/org/springframework/batch/retry/callback/ItemReaderRetryCallback.java

@@ -21,6 +21,7 @@ import org.apache.commons.logging.LogFactory;
 import org.springframework.batch.item.ItemReader;
 import org.springframework.batch.item.ItemRecoverer;
 import org.springframework.batch.item.ItemWriter;
+import org.springframework.batch.item.KeyedItemReader;
 import org.springframework.batch.retry.RetryCallback;
 import org.springframework.batch.retry.RetryContext;
 import org.springframework.batch.retry.RetryPolicy;
@@ -47,13 +48,13 @@ public class ItemReaderRetryCallback implements RetryCallback {
 	public static final String ITEM = ItemReaderRetryCallback.class.getName()
 			+ ".ITEM";
 
-	private ItemReader provider;
+	private KeyedItemReader provider;
 
 	private ItemWriter writer;
 
 	private ItemRecoverer recoverer;
 
-	public ItemReaderRetryCallback(ItemReader provider,
+	public ItemReaderRetryCallback(KeyedItemReader provider,
 			ItemWriter writer) {
 		super();
 		this.provider = provider;
@@ -127,7 +128,7 @@ public class ItemReaderRetryCallback implements RetryCallback {
 	 * 
 	 * @return the {@link ItemReader} instance.
 	 */
-	public ItemReader getReader() {
+	public KeyedItemReader getReader() {
 		return provider;
 	}
 

spring-batch-infrastructure/src/main/java/org/springframework/batch/retry/policy/ItemReaderRetryPolicy.java

@@ -19,8 +19,8 @@ package org.springframework.batch.retry.policy;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.batch.item.FailedItemIdentifier;
-import org.springframework.batch.item.ItemReader;
 import org.springframework.batch.item.ItemRecoverer;
+import org.springframework.batch.item.KeyedItemReader;
 import org.springframework.batch.repeat.synch.RepeatSynchronizationManager;
 import org.springframework.batch.retry.RetryCallback;
 import org.springframework.batch.retry.RetryContext;
@@ -109,7 +109,7 @@ public class ItemReaderRetryPolicy extends AbstractStatefulRetryPolicy {
 	public RetryContext open(RetryCallback callback) {
 		Assert.state(callback instanceof ItemReaderRetryCallback,
 				"Callback must be ItemProviderRetryCallback");
-		ItemProviderRetryContext context = new ItemProviderRetryContext(
+		ItemReaderRetryContext context = new ItemReaderRetryContext(
 				(ItemReaderRetryCallback) callback);
 		context.open(callback);
 		return context;
@@ -137,7 +137,7 @@ public class ItemReaderRetryPolicy extends AbstractStatefulRetryPolicy {
 		return ((RetryPolicy) context).handleRetryExhausted(context);
 	}
 
-	private class ItemProviderRetryContext extends RetryContextSupport
+	private class ItemReaderRetryContext extends RetryContextSupport
 			implements RetryPolicy {
 
 		private Object item;
@@ -145,11 +145,11 @@ public class ItemReaderRetryPolicy extends AbstractStatefulRetryPolicy {
 		// The delegate context...
 		private RetryContext delegateContext;
 
-		private ItemReader reader;
+		private KeyedItemReader reader;
 
 		private ItemRecoverer recoverer;
 
-		public ItemProviderRetryContext(ItemReaderRetryCallback callback) {
+		public ItemReaderRetryContext(ItemReaderRetryCallback callback) {
 			super(RetrySynchronizationManager.getContext());
 			item = callback.next(this);
 			this.reader = callback.getReader();
@@ -239,7 +239,7 @@ public class ItemReaderRetryPolicy extends AbstractStatefulRetryPolicy {
 	 * @param item
 	 * @return
 	 */
-	protected boolean hasFailed(ItemReader provider, Object item) {
+	protected boolean hasFailed(KeyedItemReader provider, Object item) {
 		if (provider instanceof FailedItemIdentifier) {
 			return ((FailedItemIdentifier) provider).hasFailed(item);
 		}