BATCH-1306:

*FieldExtractorLineAggregator now replaces nulls with empty strings before calling doAggregate().
 *PassthroughFieldExtractor no longer replaces nulls.

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

@@ -22,12 +22,12 @@ import org.springframework.util.StringUtils;
  * delimited list of strings. The default delimiter is a comma.
  * 
  * @author Dave Syer
- *
+ * 
  */
 public class DelimitedLineAggregator<T> extends ExtractorLineAggregator<T> {
 
 	private String delimiter = ",";
-	
+
 	/**
 	 * Public setter for the delimiter.
 	 * @param delimiter the delimiter to set
@@ -36,11 +36,9 @@ public class DelimitedLineAggregator<T> extends ExtractorLineAggregator<T> {
 		this.delimiter = delimiter;
 	}
 
-	/**
-	 * @see org.springframework.batch.item.file.transform.ExtractorLineAggregator#doAggregate(java.lang.Object[])
-	 */
-	public String doAggregate(Object[] item) {
-		return StringUtils.arrayToDelimitedString(item, this.delimiter);
+	@Override
+	public String doAggregate(Object[] fields) {
+		return StringUtils.arrayToDelimitedString(fields, this.delimiter);
 	}
 
 }

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

@@ -43,13 +43,29 @@ public abstract class ExtractorLineAggregator<T> implements LineAggregator<T> {
 
 	/**
 	 * Extract fields from the given item using the {@link FieldExtractor} and
-	 * then aggregate them.  Null items are not allowed.
+	 * then aggregate them. Any null field returned by the extractor will be
+	 * replaced by an empty String. Null items are not allowed.
 	 * 
 	 * @see org.springframework.batch.item.file.transform.LineAggregator#aggregate(java.lang.Object)
 	 */
 	public String aggregate(T item) {
 		Assert.notNull(item);
-		return this.doAggregate(this.fieldExtractor.extract(item));
+		Object[] fields = this.fieldExtractor.extract(item);
+
+		//
+		// Replace nulls with empty strings
+		//
+		Object[] args = new Object[fields.length];
+		for (int i = 0; i < fields.length; i++) {
+			if (fields[i] == null) {
+				args[i] = "";
+			}
+			else {
+				args[i] = fields[i];
+			}
+		}
+
+		return this.doAggregate(args);
 	}
 
 	/**

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

@@ -67,7 +67,6 @@ public class FormatterLineAggregator<T> extends ExtractorLineAggregator<T> {
 		this.format = format;
 	}
 
-
 	/**
 	 * Public setter for the locale.
 	 * @param locale the locale to set
@@ -76,9 +75,7 @@ public class FormatterLineAggregator<T> extends ExtractorLineAggregator<T> {
 		this.locale = locale;
 	}
 
-	/**
-	 * @see org.springframework.batch.item.file.transform.ExtractorLineAggregator#doAggregate(java.lang.Object[])
-	 */
+	@Override
 	protected String doAggregate(Object[] fields) {
 
 		Assert.notNull(format);

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

@@ -34,31 +34,13 @@ public class PassThroughFieldExtractor<T> implements FieldExtractor<T> {
 	public Object[] extract(T item) {
 
 		if (item.getClass().isArray()) {
-			Object[] items = (Object[]) item;
-			Object[] args = new Object[items.length];
-			for (int i = 0; i < items.length; i++) {
-				if (items[i] == null)
-					args[i] = "";
-				else
-					args[i] = items[i];
-			}
-			return args;
+			return (Object[]) item;
 		}
 
 		if (item instanceof Collection<?>) {
-			Collection<?> items = (Collection<?>) item;
-			Object[] args = new Object[items.size()];
-			int i = 0;
-			for (Object object : items) {
-				if (object == null)
-					args[i] = "";
-				else
-					args[i] = object;
-				i++;
-			}
-			return args;
+			return ((Collection<?>) item).toArray();
 		}
-		
+
 		if (item instanceof FieldSet) {
 			return ((FieldSet) item).getValues();
 		}