Polish 62a2e65

Add null check for delimiter

Author: fmbenhassine

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

@@ -462,7 +462,9 @@ public DelimitedLineAggregator<T> build() {
 					"A list of field names or a field extractor is required");
 
 			DelimitedLineAggregator<T> delimitedLineAggregator = new DelimitedLineAggregator<>();
-			delimitedLineAggregator.setDelimiter(this.delimiter);
+			if (this.delimiter != null) {
+				delimitedLineAggregator.setDelimiter(this.delimiter);
+			}
 
 			if (this.fieldExtractor == null) {
 				BeanWrapperFieldExtractor<T> beanWrapperFieldExtractor = new BeanWrapperFieldExtractor<>();

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

@@ -129,7 +129,7 @@ public void testDelimitedOutputWithEmptyDelimiter() throws Exception {
 				.lineSeparator("$")
 				.delimited()
 				.delimiter("")
-				.names("first", "second", "third")
+				.names(new String[] {"first", "second", "third"})
 				.encoding("UTF-16LE")
 				.headerCallback(writer1 -> writer1.append("HEADER"))
 				.footerCallback(writer12 -> writer12.append("FOOTER"))