Move to next sheet when there are only empty/invalid rows (#82)

When there are blank or empty lines in the end of one sheet, null is returned by doRead without trying to read next sheet. A recursive call makes sheet moving happen when another exists.

Co-authored-by: Mahmoud Ben Hassine <mbenhassine@vmware.com>
Co-authored-by: cesar.alves@gmail.com <coa@pc-coa.caso.pt>

spring-batch-excel/src/main/java/org/springframework/batch/extensions/excel/AbstractExcelItemReader.java

@@ -107,7 +107,7 @@ public abstract class AbstractExcelItemReader<T> extends AbstractItemCountingIte
 			this.rs.next();
 		}
 		try {
-			return (this.rs.getCurrentRow() != null) ? this.rowMapper.mapRow(this.rs) : null;
+			return (this.rs.getCurrentRow() != null) ? this.rowMapper.mapRow(this.rs) : doRead();
 		}
 		catch (Exception ex) {
 			throw new ExcelFileParseException("Exception parsing Excel file.", ex, this.resource.getDescription(),

spring-batch-excel/src/test/java/org/springframework/batch/extensions/excel/poi/PoiItemReaderXlsWithBlankLinesTests.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2002-2014 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.batch.extensions.excel.poi;
+
+import org.springframework.batch.extensions.excel.AbstractExcelItemReader;
+import org.springframework.batch.extensions.excel.AbstractExcelItemReaderTests;
+import org.springframework.core.io.ClassPathResource;
+
+/**
+ * @author Marten Deinum
+ * @since 0.1.0
+ */
+public class PoiItemReaderXlsWithBlankLinesTests extends AbstractExcelItemReaderTests {
+
+	@Override
+	protected void configureItemReader(AbstractExcelItemReader<String[]> itemReader) {
+		itemReader.setResource(new ClassPathResource("player_with_blank_lines.xls"));
+	}
+
+	@Override
+	protected AbstractExcelItemReader<String[]> createExcelItemReader() {
+		return new PoiItemReader<>();
+	}
+
+}