BATCH-1854 Created ResourceAware and added a check to MultiResourceItemReader. If an item implements ResourceAware, the current resource will be set on it

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

@@ -0,0 +1,16 @@
+package org.springframework.batch.item;
+
+import org.springframework.core.io.Resource;
+import org.springframework.batch.item.file.MultiResourceItemReader;
+
+/**
+ * Marker interface indicating that an item should have the Spring {@link Resource} in which it was read from, set on it.
+ * The canonical example is within {@link MultiResourceItemReader}, which will set the current resource on any items
+ * that implement this interface.
+ *
+ * @author Lucas Ward
+ */
+public interface ResourceAware {
+
+    void setResource(Resource resource);
+}

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

@@ -21,12 +21,7 @@ import java.util.Comparator;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.springframework.batch.item.ExecutionContext;
-import org.springframework.batch.item.ItemReader;
-import org.springframework.batch.item.ItemStream;
-import org.springframework.batch.item.ItemStreamException;
-import org.springframework.batch.item.ParseException;
-import org.springframework.batch.item.UnexpectedInputException;
+import org.springframework.batch.item.*;
 import org.springframework.batch.item.util.ExecutionContextUserSupport;
 import org.springframework.core.io.Resource;
 import org.springframework.util.Assert;
@@ -116,7 +111,7 @@ public class MultiResourceItemReader<T> implements ItemReader<T>, ItemStream {
 	 */
 	private T readNextItem() throws Exception {
 
-		T item = delegate.read();
+		T item = readFromDelegate();
 
 		while (item == null) {
 
@@ -130,13 +125,21 @@ public class MultiResourceItemReader<T> implements ItemReader<T>, ItemStream {
 			delegate.setResource(resources[currentResource]);
 			delegate.open(new ExecutionContext());
 
-			item = delegate.read();
-		}
+            item = readFromDelegate();
+        }
 
 		return item;
 	}
 
-	/**
+    private T readFromDelegate() throws Exception {
+        T item = delegate.read();
+        if(item instanceof ResourceAware){
+            ((ResourceAware) item).setResource(getCurrentResource());
+        }
+        return item;
+    }
+
+    /**
 	 * Close the {@link #setDelegate(ResourceAwareItemReaderItemStream)} reader and reset instance variable values.
 	 */
 	public void close() throws ItemStreamException {

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/file/MultiResourceItemReaderResourceAwareTests.java

@@ -0,0 +1,108 @@
+package org.springframework.batch.item.file;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStreamException;
+import org.springframework.batch.item.ResourceAware;
+import org.springframework.batch.item.file.mapping.PassThroughLineMapper;
+import org.springframework.core.io.AbstractResource;
+import org.springframework.core.io.ByteArrayResource;
+import org.springframework.core.io.FileSystemResource;
+import org.springframework.core.io.Resource;
+import org.springframework.test.util.ReflectionTestUtils;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Comparator;
+
+import static org.junit.Assert.*;
+
+/**
+ * Tests to ensure that the current Resource is correctly being set on items that implement ResourceAware.
+ * Because it there are extensive tests the reader in general, this will only test ResourceAware related
+ * use cases.
+ */
+public class MultiResourceItemReaderResourceAwareTests {
+
+	private MultiResourceItemReader<Foo> tested = new MultiResourceItemReader<Foo>();
+
+	private FlatFileItemReader<Foo> itemReader = new FlatFileItemReader<Foo>();
+
+	private ExecutionContext ctx = new ExecutionContext();
+
+	// test input spans several resources
+	private Resource r1 = new ByteArrayResource("1\n2\n3\n".getBytes());
+
+	private Resource r2 = new ByteArrayResource("4\n5\n".getBytes());
+
+	private Resource r3 = new ByteArrayResource("".getBytes());
+
+	private Resource r4 = new ByteArrayResource("6\n".getBytes());
+
+	private Resource r5 = new ByteArrayResource("7\n8\n".getBytes());
+
+	/**
+	 * Setup the tested reader to read from the test resources.
+	 */
+	@Before
+	public void setUp() throws Exception {
+
+		itemReader.setLineMapper(new FooLineMapper());
+
+		tested.setDelegate(itemReader);
+		tested.setComparator(new Comparator<Resource>() {
+			public int compare(Resource o1, Resource o2) {
+				return 0; // do not change ordering
+			}
+		});
+		tested.setResources(new Resource[] { r1, r2, r3, r4, r5 });
+	}
+
+	/**
+	 * Read input from start to end.
+	 */
+	@Test
+	public void testRead() throws Exception {
+
+		tested.open(ctx);
+
+        assertValueAndResource(r1, "1");
+        assertValueAndResource(r1, "2");
+        assertValueAndResource(r1, "3");
+        assertValueAndResource(r2, "4");
+        assertValueAndResource(r2, "5");
+        assertValueAndResource(r4, "6");
+        assertValueAndResource(r5, "7");
+        assertValueAndResource(r5, "8");
+        assertEquals(null, tested.read());
+
+		tested.close();
+	}
+
+    private void assertValueAndResource(Resource expectedResource, String expectedValue) throws Exception {
+        Foo foo = tested.read();
+        assertEquals(expectedValue, foo.value);
+        assertEquals(expectedResource, foo.resource);
+    }
+
+    static final class FooLineMapper implements LineMapper<Foo> {
+        public Foo mapLine(String line, int lineNumber) throws Exception {
+            return new Foo(line);
+        }
+    }
+
+    static final class Foo implements ResourceAware {
+
+        String value;
+        Resource resource;
+
+        Foo(String value) {
+            this.value = value;
+        }
+
+        public void setResource(Resource resource) {
+            this.resource = resource;
+        }
+    }
+}