Updated based on code review.

Author: cppwfs

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2021 the original author or authors.
+ * Copyright 2006-2018 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.
@@ -16,7 +16,6 @@
 
 package org.springframework.batch.item.file;
 
-import java.nio.charset.Charset;
 import java.util.List;
 
 import org.springframework.batch.item.file.transform.LineAggregator;
@@ -40,15 +39,11 @@
  * @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/main/java/org/springframework/batch/item/support/AbstractFileItemWriter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2018 the original author or authors.
+ * Copyright 2006-2021 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.
@@ -23,6 +23,7 @@
 import java.io.Writer;
 import java.nio.channels.Channels;
 import java.nio.channels.FileChannel;
+import java.nio.charset.Charset;
 import java.nio.charset.UnsupportedCharsetException;
 import java.util.List;
 
@@ -59,6 +60,7 @@
  * @author Dave Syer
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
+ * @author Glenn Renfro
  *
  * @since 4.1
  */
@@ -71,8 +73,8 @@ public abstract class AbstractFileItemWriter<T> extends AbstractItemStreamItemWr
 
 	public static final String DEFAULT_LINE_SEPARATOR = System.getProperty("line.separator");
 
-	// default encoding for writing to output files - set to UTF-8.
-	public static final String DEFAULT_CHARSET = "UTF-8";
+	// default encoding for writing to flat files - set to charset of this Java virtual machine.
+	public static final String DEFAULT_CHARSET = Charset.defaultCharset().name();
 
 	private static final String WRITTEN_STATISTICS_NAME = "written";
 

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

@@ -25,6 +25,7 @@
 import org.junit.Test;
 
 import org.springframework.batch.item.ExecutionContext;
+
 import org.springframework.batch.item.file.FlatFileItemWriter;
 import org.springframework.batch.item.file.transform.PassThroughLineAggregator;
 import org.springframework.core.io.FileSystemResource;
@@ -266,8 +267,31 @@ public void testFlags() throws Exception {
 
 		Resource output = new FileSystemResource(File.createTempFile("foo", "txt"));
 
+		String encoding = Charset.defaultCharset().name();
+
+		FlatFileItemWriter<Foo> writer = new FlatFileItemWriterBuilder<Foo>()
+				.name("foo")
+				.resource(output)
+				.shouldDeleteIfEmpty(true)
+				.shouldDeleteIfExists(false)
+				.saveState(false)
+				.forceSync(true)
+				.append(true)
+				.transactional(false)
+				.lineAggregator(new PassThroughLineAggregator<>())
+				.build();
+
+		validateBuilderFlags(writer, encoding);
+	}
+
+	@Test
+	public void testFlagsWithEncoding() throws Exception {
+
+		Resource output = new FileSystemResource(File.createTempFile("foo", "txt"));
+		String encoding = "UTF-8";
 		FlatFileItemWriter<Foo> writer = new FlatFileItemWriterBuilder<Foo>()
 				.name("foo")
+				.encoding("UTF-8")
 				.resource(output)
 				.shouldDeleteIfEmpty(true)
 				.shouldDeleteIfExists(false)
@@ -277,16 +301,21 @@ public void testFlags() throws Exception {
 				.transactional(false)
 				.lineAggregator(new PassThroughLineAggregator<>())
 				.build();
+		validateBuilderFlags(writer, encoding);
+	}
+
+	private void validateBuilderFlags(FlatFileItemWriter<Foo> writer, String encoding) {
 		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(), ReflectionTestUtils.getField(writer, "encoding"));
+		assertEquals( encoding, ReflectionTestUtils.getField(writer, "encoding"));
 	}
 
-	private String readLine(String encoding, Resource outputFile ) throws IOException {
+
+		private String readLine(String encoding, Resource outputFile ) throws IOException {
 
 		if (reader == null) {
 			reader = new BufferedReader(new InputStreamReader(outputFile.getInputStream(), encoding));

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/json/builder/JsonFileItemWriterBuilderTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2018 the original author or authors.
+ * Copyright 2018-2021 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.
@@ -17,6 +17,7 @@
 package org.springframework.batch.item.json.builder;
 
 import java.io.File;
+import java.nio.charset.Charset;
 import java.nio.file.Files;
 
 import org.junit.Before;
@@ -36,6 +37,7 @@
 
 /**
  * @author Mahmoud Ben Hassine
+ * @author Glenn Renfro
  */
 public class JsonFileItemWriterBuilderTest {
 
@@ -100,7 +102,45 @@ public void testJsonFileItemWriterCreation() {
 				.transactional(transactional)
 				.build();
 
-		// then
+		//then
+		validateBuilderFlags(writer, encoding, lineSeparator, headerCallback, footerCallback);
+	}
+
+	@Test
+	public void testJsonFileItemWriterCreationDefaultEncoding() {
+		// given
+		boolean append = true;
+		boolean forceSync = true;
+		boolean transactional = true;
+		boolean shouldDeleteIfEmpty = true;
+		boolean shouldDeleteIfExists = true;
+		String encoding = Charset.defaultCharset().name();
+		String lineSeparator = "#";
+		FlatFileHeaderCallback headerCallback = Mockito.mock(FlatFileHeaderCallback.class);
+		FlatFileFooterCallback footerCallback = Mockito.mock(FlatFileFooterCallback.class);
+
+		// when
+		JsonFileItemWriter<String> writer = new JsonFileItemWriterBuilder<String>()
+				.name("jsonFileItemWriter")
+				.resource(this.resource)
+				.jsonObjectMarshaller(this.jsonObjectMarshaller)
+				.append(append)
+				.forceSync(forceSync)
+				.headerCallback(headerCallback)
+				.footerCallback(footerCallback)
+				.lineSeparator(lineSeparator)
+				.shouldDeleteIfEmpty(shouldDeleteIfEmpty)
+				.shouldDeleteIfExists(shouldDeleteIfExists)
+				.transactional(transactional)
+				.build();
+
+		//then
+		validateBuilderFlags(writer, encoding, lineSeparator, headerCallback, footerCallback);
+	}
+
+	private void validateBuilderFlags(JsonFileItemWriter<String> writer, String encoding,
+			String lineSeparator, FlatFileHeaderCallback headerCallback,
+			FlatFileFooterCallback footerCallback) {
 		assertTrue((Boolean) ReflectionTestUtils.getField(writer, "saveState"));
 		assertTrue((Boolean) ReflectionTestUtils.getField(writer, "append"));
 		assertTrue((Boolean) ReflectionTestUtils.getField(writer, "transactional"));