RESOLVED - issue BATCH-1317: Add flag to FlatFileItemWriter to delete empty files

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

@@ -77,6 +77,8 @@ public class FlatFileItemWriter<T> extends ExecutionContextUserSupport implement
 
 	private boolean shouldDeleteIfExists = true;
 
+	private boolean shouldDeleteIfEmpty = false;
+
 	private String encoding = OutputState.DEFAULT_CHARSET;
 
 	private FlatFileHeaderCallback headerCallback;
@@ -134,12 +136,27 @@ public class FlatFileItemWriter<T> extends ExecutionContextUserSupport implement
 	}
 
 	/**
-	 * @param shouldDeleteIfExists the shouldDeleteIfExists to set
+	 * Flag to indicate that the target file should be deleted if it already
+	 * exists, otherwise it will be appended. If headers are emitted then
+	 * appending will cause them to show up in the middle of the file. Defaults
+	 * to true (so no appending except on restart).
+	 * 
+	 * @param shouldDeleteIfExists the flag value to set
 	 */
 	public void setShouldDeleteIfExists(boolean shouldDeleteIfExists) {
 		this.shouldDeleteIfExists = shouldDeleteIfExists;
 	}
 
+	/**
+	 * Flag to indicate that the target file should be deleted if no lines have
+	 * been written (other than header and footer) on close. Defaults to false.
+	 * 
+	 * @param shouldDeleteIfEmpty the flag value to set
+	 */
+	public void setShouldDeleteIfEmpty(boolean shouldDeleteIfEmpty) {
+		this.shouldDeleteIfEmpty = shouldDeleteIfEmpty;
+	}
+
 	/**
 	 * Set the flag indicating whether or not state should be saved in the
 	 * provided {@link ExecutionContext} during the {@link ItemStream} call to
@@ -220,10 +237,18 @@ public class FlatFileItemWriter<T> extends ExecutionContextUserSupport implement
 				}
 			}
 			catch (IOException e) {
-				throw new ItemStreamException("Failed to writer footer before closing", e);
+				throw new ItemStreamException("Failed to write footer before closing", e);
 			}
 			finally {
-				getOutputState().close();
+				state.close();
+				if (state.linesWritten == 0 && shouldDeleteIfEmpty) {
+					try {
+						resource.getFile().delete();
+					}
+					catch (IOException e) {
+						throw new ItemStreamException("Failed to delete empty file on close", e);
+					}
+				}
 				state = null;
 			}
 		}
@@ -350,7 +375,7 @@ public class FlatFileItemWriter<T> extends ExecutionContextUserSupport implement
 			}
 
 			outputBufferedWriter.flush();
-			pos = fileChannel.position() + ((TransactionAwareBufferedWriter)outputBufferedWriter).getBufferSize();
+			pos = fileChannel.position() + ((TransactionAwareBufferedWriter) outputBufferedWriter).getBufferSize();
 
 			return pos;
 
@@ -386,16 +411,33 @@ public class FlatFileItemWriter<T> extends ExecutionContextUserSupport implement
 			initialized = false;
 			restarted = false;
 			try {
-				if (outputBufferedWriter == null) {
-					return;
+				if (outputBufferedWriter != null) {
+					outputBufferedWriter.close();
 				}
-				outputBufferedWriter.close();
-				fileChannel.close();
-				os.close();
 			}
 			catch (IOException ioe) {
 				throw new ItemStreamException("Unable to close the the ItemWriter", ioe);
 			}
+			finally {
+				try {
+					if (fileChannel != null) {
+						fileChannel.close();
+					}
+				}
+				catch (IOException ioe) {
+					throw new ItemStreamException("Unable to close the the ItemWriter", ioe);
+				}
+				finally {
+					try {
+						if (os != null) {
+							os.close();
+						}
+					}
+					catch (IOException ioe) {
+						throw new ItemStreamException("Unable to close the the ItemWriter", ioe);
+					}
+				}
+			}
 		}
 
 		/**

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

@@ -61,7 +61,9 @@ public class FileUtils {
 					if (!overwriteOutputFile) {
 						throw new ItemStreamException("File already exists: [" + file.getAbsolutePath() + "]");
 					}
-					file.delete();
+					if (!file.delete()) {
+						throw new IOException("Could not delete file: "+file);
+					}
 				}
 
 				if (file.getParent() != null) {

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

@@ -370,19 +370,26 @@ public class FlatFileItemWriterTests {
 	@Test
 	public void testWriteStringWithBogusEncoding() throws Exception {
 		writer.setEncoding("BOGUS");
+		// writer.setShouldDeleteIfEmpty(true);
 		try {
 			writer.open(executionContext);
-			fail("Expecyted ItemStreamException");
+			fail("Expected ItemStreamException");
 		}
 		catch (ItemStreamException e) {
 			assertTrue(e.getCause() instanceof UnsupportedCharsetException);
 		}
 		writer.close();
+		// Try and write after the exception on open:
+		writer.setEncoding("UTF-8");
+		writer.open(executionContext);
+		writer.write(Collections.singletonList(TEST_STRING));
 	}
 
 	@Test
 	public void testWriteStringWithEncodingAfterClose() throws Exception {
-		testWriteStringWithBogusEncoding();
+		writer.open(executionContext);
+		writer.write(Collections.singletonList(TEST_STRING));
+		writer.close();
 		writer.setEncoding("UTF-8");
 		writer.open(executionContext);
 		writer.write(Collections.singletonList(TEST_STRING));
@@ -428,6 +435,22 @@ public class FlatFileItemWriterTests {
 		assertEquals(TEST_STRING, lineFromFile);
 	}
 
+	@Test
+	public void testWriteHeaderAndDeleteOnExit() throws Exception {
+		writer.setHeaderCallback(new FlatFileHeaderCallback() {
+
+			public void writeHeader(Writer writer) throws IOException {
+				writer.write("a\nb");
+			}
+
+		});
+		writer.setShouldDeleteIfEmpty(true);
+		writer.open(executionContext);
+		assertTrue(outputFile.exists());
+		writer.close();
+		assertFalse(outputFile.exists());
+	}
+
 	@Test
 	public void testWriteHeaderAfterRestartOnFirstChunk() throws Exception {
 		writer.setHeaderCallback(new FlatFileHeaderCallback() {