RESOLVED - issue BATCH-205: support for processing chain

http://opensource.atlassian.com/projects/spring/browse/BATCH-205

Patch applied.

infrastructure/src/main/java/org/springframework/batch/item/processor/CompositeItemTransformer.java

@@ -0,0 +1,42 @@
+package org.springframework.batch.item.processor;
+
+import java.util.Iterator;
+import java.util.List;
+
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.util.Assert;
+
+/**
+ * Composite {@link ItemTransformer} that passes the item through a sequence
+ * of injected <code>ItemTransformer</code>s (return value of previous transformation
+ * is the entry value of the next).
+ * 
+ * @author Robert Kasanicky
+ */
+public class CompositeItemTransformer implements ItemTransformer, InitializingBean {
+
+	private List itemTransformers;
+	
+	public Object transform(Object item) {
+		Object result = item;
+		for (Iterator iterator = itemTransformers.listIterator(); iterator.hasNext();) {
+			result = ((ItemTransformer)iterator.next()).transform(result);	
+		}
+		return result;
+	}
+
+	public void afterPropertiesSet() throws Exception {
+		Assert.notEmpty(itemTransformers);
+		for (Iterator iterator = itemTransformers.iterator(); iterator.hasNext();) {
+			Assert.isInstanceOf(ItemTransformer.class, iterator.next());
+		}
+	}
+
+	/**
+	 * @param itemTransformers will be chained to produce a composite transformation.
+	 */
+	public void setItemTransformers(List itemTransformers) {
+		this.itemTransformers = itemTransformers;
+	}
+
+}

infrastructure/src/main/java/org/springframework/batch/item/processor/ItemTransformer.java

@@ -0,0 +1,11 @@
+package org.springframework.batch.item.processor;
+
+/**
+ * Interface for item transformations during processing phase.
+ * 
+ * @author Robert Kasanicky
+ */
+public interface ItemTransformer {
+
+	Object transform(Object item);
+}

infrastructure/src/main/java/org/springframework/batch/item/processor/OutputSourceItemProcessor.java

@@ -9,6 +9,7 @@ import org.springframework.batch.restart.GenericRestartData;
 import org.springframework.batch.restart.RestartData;
 import org.springframework.batch.restart.Restartable;
 import org.springframework.batch.statistics.StatisticsProvider;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.util.Assert;
 
 /**
@@ -16,23 +17,33 @@ import org.springframework.util.Assert;
  * {@link StatisticsProvider} where the {@link OutputSource} does.
  * 
  * @author Dave Syer
+ * @author Robert Kasanicky
  */
 public class OutputSourceItemProcessor implements ItemProcessor, Restartable, Skippable,
-		StatisticsProvider {
+		StatisticsProvider, InitializingBean {
 
 	private OutputSource source;
 
-	/* (non-Javadoc)
+	/**
+	 * Calls {@link #doProcess(Object)} and then writes the result to the output source.
+	 * 
 	 * @see org.springframework.batch.item.ItemProcessor#process(java.lang.Object)
 	 */
-	public void process(Object data) throws Exception {
-		source.write(data);
+	final public void process(Object item) throws Exception {
+		Object result = doProcess(item);
+		source.write(result);
+	}
+
+	/**
+	 * By default returns the argument. This method is an extension point
+	 * meant to be overridden by subclasses that implement processing logic. 
+	 */
+	protected Object doProcess(Object item) {
+		return item;
 	}
 
 	/**
 	 * Setter for output source.
-	 * 
-	 * @param source
 	 */
 	public void setOutputSource(OutputSource source) {
 		this.source = source;
@@ -85,4 +96,9 @@ public class OutputSourceItemProcessor implements ItemProcessor, Restartable, Sk
 		}
 	}
 
+	
+	public void afterPropertiesSet() throws Exception {
+		Assert.notNull(source);
+	}
+
 }

infrastructure/src/main/java/org/springframework/batch/item/processor/TransformerOutputSourceItemProcessor.java

@@ -0,0 +1,35 @@
+package org.springframework.batch.item.processor;
+
+import org.springframework.batch.io.OutputSource;
+import org.springframework.util.Assert;
+
+/**
+ * Transforms the item using injected {@link ItemTransformer}
+ * before it is written to output by {@link OutputSource}.
+ * 
+ * @author Robert Kasanicky
+ */
+public class TransformerOutputSourceItemProcessor extends OutputSourceItemProcessor {
+
+	private ItemTransformer itemTransformer;
+
+	/**
+	 * Transform the item using the {@link #itemTransformer}.
+	 */
+	protected Object doProcess(Object item) {
+		return itemTransformer.transform(item);
+	}
+
+	/**
+	 * @param itemTransformer will transform the item before
+	 * it is passed to {@link OutputSource}.
+	 */
+	public void setItemTransformer(ItemTransformer itemTransformer) {
+		this.itemTransformer = itemTransformer;
+	}
+
+	public void afterPropertiesSet() throws Exception {
+		super.afterPropertiesSet();
+		Assert.notNull(itemTransformer);
+	}
+}

infrastructure/src/test/java/org/springframework/batch/item/processor/CompositeItemTransformerTests.java

@@ -0,0 +1,95 @@
+package org.springframework.batch.item.processor;
+
+import java.util.ArrayList;
+
+import junit.framework.TestCase;
+
+import org.easymock.MockControl;
+
+/**
+ * Tests for {@link CompositeItemTransformer}.
+ * 
+ * @author Robert Kasanicky
+ */
+public class CompositeItemTransformerTests extends TestCase {
+
+	private CompositeItemTransformer composite = new CompositeItemTransformer();
+	
+	private ItemTransformer transformer1;
+	private ItemTransformer transformer2;
+
+	private MockControl tControl1 = MockControl.createControl(ItemTransformer.class);
+	private MockControl tControl2 = MockControl.createControl(ItemTransformer.class);
+	
+	protected void setUp() throws Exception {
+		transformer1 = (ItemTransformer) tControl1.getMock();
+		transformer2 = (ItemTransformer) tControl2 .getMock();
+		
+		composite.setItemTransformers(new ArrayList() {{ 
+			add(transformer1); add(transformer2); 
+		}});
+		
+		composite.afterPropertiesSet();
+	}
+	
+	/**
+	 * Regular usage scenario - item is passed through the processing chain,
+	 * return value of the of the last transformation is returned by the composite.
+	 */
+	public void testTransform() throws Exception {
+		Object item = new Object();
+		Object itemAfterFirstTransfromation = new Object();
+		Object itemAfterSecondTransformation = new Object();
+
+		transformer1.transform(item);
+		tControl1.setReturnValue(itemAfterFirstTransfromation);
+		
+		transformer2.transform(itemAfterFirstTransfromation);
+		tControl2.setReturnValue(itemAfterSecondTransformation);
+		
+		tControl1.replay();
+		tControl2.replay();
+
+		assertSame(itemAfterSecondTransformation, composite.transform(item));
+
+		tControl1.verify();
+		tControl2.verify();
+	}
+	
+	/**
+	 * The list of transformers must not be null or empty and 
+	 * can contain only instances of {@link ItemTransformer}.
+	 */
+	public void testAfterPropertiesSet() throws Exception {
+		
+		// value not set
+		composite.setItemTransformers(null);
+		try {
+			composite.afterPropertiesSet();
+			fail();
+		}
+		catch (IllegalArgumentException e) {
+			// expected
+		}
+		
+		// empty list
+		composite.setItemTransformers(new ArrayList());
+		try {
+			composite.afterPropertiesSet();
+			fail();
+		}
+		catch (IllegalArgumentException e) {
+			// expected
+		}
+		
+		// invalid list member
+		composite.setItemTransformers(new ArrayList() {{ add(new Object()); }});
+		try {
+			composite.afterPropertiesSet();
+			fail();
+		}
+		catch (IllegalArgumentException e) {
+			// expected
+		}
+	}
+}

infrastructure/src/test/java/org/springframework/batch/item/processor/OutputSourceItemProcessorTests.java

@@ -47,6 +47,7 @@ public class OutputSourceItemProcessorTests extends TestCase {
 	protected void setUp() throws Exception {
 		source = new MockOutputSource("test");
 		processor.setOutputSource(source);
+		processor.afterPropertiesSet();
 	}
 
 	public void testProcess() throws Exception {
@@ -126,6 +127,20 @@ public class OutputSourceItemProcessorTests extends TestCase {
 		assertEquals("after skip", list.get(0));
 	}
 
+	/**
+	 * Output source property must be set.
+	 */
+	public void testAfterPropertiesSet() throws Exception {
+		processor.setOutputSource(null);
+		try {
+			processor.afterPropertiesSet();
+			fail();
+		}
+		catch (IllegalArgumentException e) {
+			// expected
+		}
+	}
+	
 	private List list = new ArrayList(); 
 
 	/**

infrastructure/src/test/java/org/springframework/batch/item/processor/TransformerOutputSourceItemProcessorTests.java

@@ -0,0 +1,71 @@
+package org.springframework.batch.item.processor;
+
+import junit.framework.TestCase;
+
+import org.easymock.MockControl;
+import org.springframework.batch.io.OutputSource;
+
+/**
+ * Tests for {@link TransformerOutputSourceItemProcessor}.
+ * 
+ * @author Robert Kasanicky
+ */
+public class TransformerOutputSourceItemProcessorTests extends TestCase {
+
+	private TransformerOutputSourceItemProcessor processor = new TransformerOutputSourceItemProcessor();
+
+	private ItemTransformer transformer;
+	private OutputSource outputSource;
+
+	private MockControl tControl = MockControl.createControl(ItemTransformer.class);
+	private MockControl outControl = MockControl.createControl(OutputSource.class);
+
+	protected void setUp() throws Exception {
+		transformer = (ItemTransformer) tControl.getMock();
+		outputSource = (OutputSource) outControl.getMock();
+		
+		processor.setItemTransformer(transformer);
+		processor.setOutputSource(outputSource);
+		
+		processor.afterPropertiesSet();
+	}
+
+	/**
+	 * Regular usage scenario - item is passed to transformer
+	 * and the result of transformation is passed to output source.
+	 */
+	public void testProcess() throws Exception {
+		Object item = new Object();
+		Object itemAfterTransformation = new Object();
+
+		transformer.transform(item);
+		tControl.setReturnValue(itemAfterTransformation);
+		
+		outputSource.write(itemAfterTransformation);
+		outControl.setVoidCallable();
+		
+		tControl.replay();
+		outControl.replay();
+
+		processor.process(item);
+
+		tControl.verify();
+		outControl.verify();
+	}
+	
+	/**
+	 * Item transformer must be set.
+	 */
+	public void testAfterPropertiesSet() throws Exception {
+		
+		// value not set
+		processor.setItemTransformer(null);
+		try {
+			processor.afterPropertiesSet();
+			fail();
+		}
+		catch (IllegalArgumentException e) {
+			// expected
+		}
+	}
+}