FlatFileItemWriter now uses charset to determine default encoding

resolves #1154

It now matches the encoding scheme of FlatFileItemReader

Author: cppwfs

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

@@ -16,6 +16,7 @@
 
 package org.springframework.batch.item.file;
 
+import java.nio.charset.Charset;
 import java.util.List;
 
 import org.springframework.batch.item.file.transform.LineAggregator;
@@ -39,11 +40,15 @@
  * @author Dave Syer
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
+ * @author Glenn Renfro
  */
 public class FlatFileItemWriter<T> extends AbstractFileItemWriter<T> {
 
 	protected LineAggregator<T> lineAggregator;
 
+	// default encoding for writing to flat files - set to charset of this Java virtual machine.
+	public static final String DEFAULT_CHARSET = Charset.defaultCharset().name();
+
 	public FlatFileItemWriter() {
 		this.setExecutionContextName(ClassUtils.getShortName(FlatFileItemWriter.class));
 	}

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

@@ -19,6 +19,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStreamReader;
+import java.nio.charset.Charset;
 import java.util.Arrays;
 
 import org.junit.Test;
@@ -275,13 +276,13 @@ public void testFlags() throws Exception {
 				.transactional(false)
 				.lineAggregator(new PassThroughLineAggregator<>())
 				.build();
-
 		assertFalse((Boolean) ReflectionTestUtils.getField(writer, "saveState"));
 		assertTrue((Boolean) ReflectionTestUtils.getField(writer, "append"));
 		assertFalse((Boolean) ReflectionTestUtils.getField(writer, "transactional"));
 		assertTrue((Boolean) ReflectionTestUtils.getField(writer, "shouldDeleteIfEmpty"));
 		assertFalse((Boolean) ReflectionTestUtils.getField(writer, "shouldDeleteIfExists"));
 		assertTrue((Boolean) ReflectionTestUtils.getField(writer, "forceSync"));
+		assertEquals( Charset.defaultCharset().name(), (String) ReflectionTestUtils.getField(writer, "encoding"));
 	}
 
 	private String readLine(String encoding, Resource outputFile ) throws IOException {