Added ability to fill a vertically-filled page with blank data rows.

jasperreports/src/net/sf/jasperreports/engine/JRParameter.java

@@ -262,6 +262,11 @@ public interface JRParameter extends JRPropertiesHolder, JRCloneable
 	 */
 	public static final String REPORT_FORMAT_FACTORY = "REPORT_FORMAT_FACTORY";
 
+	/**
+	 * An option allowing the remainder of a vertically-filled report's detail section to be filled with blank rows of
+	 * data when the main data set is exhausted.
+	 */
+	public static final String REPORT_FILL_DETAIL_WITH_BLANK_ROWS = "REPORT_FILL_DETAIL_WITH_BLANK_ROWS";
 
 	/**
 	 * This built-in flag parameter specifies whether to ignore pagination.

jasperreports/src/net/sf/jasperreports/engine/fill/JRBaseFiller.java

@@ -1194,6 +1194,13 @@ protected boolean next() throws JRException
 		return mainDataset.next();
 	}
 
+	/**
+	 * @return whether elements should evaluate as blank
+	 */
+	protected boolean evaluateElementToBlank() {
+		return false;
+	}
+
 	/**
 	 * Resolves elements which are to be evaluated at report level.
 	 */

jasperreports/src/net/sf/jasperreports/engine/fill/JRFillElement.java

@@ -1166,6 +1166,9 @@ protected boolean delayedEvaluationUpdatesTemplate()
 	 */
 	public final Object evaluateExpression(JRExpression expression, byte evaluation) throws JRException
 	{
+		if (filler.evaluateElementToBlank()) {
+			return null;
+		}
 		return expressionEvaluator.evaluate(expression, evaluation);
 	}
 

jasperreports/src/net/sf/jasperreports/engine/fill/JRVerticalFiller.java

@@ -23,14 +23,18 @@
  */
 package net.sf.jasperreports.engine.fill;
 
+import java.util.Map;
+
 import org.apache.commons.javaflow.api.continuable;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
 import net.sf.jasperreports.engine.JRException;
 import net.sf.jasperreports.engine.JRExpression;
 import net.sf.jasperreports.engine.JRGroup;
+import net.sf.jasperreports.engine.JRParameter;
 import net.sf.jasperreports.engine.JRRuntimeException;
+import net.sf.jasperreports.engine.JasperPrint;
 import net.sf.jasperreports.engine.JasperReport;
 import net.sf.jasperreports.engine.JasperReportsContext;
 import net.sf.jasperreports.engine.type.FooterPositionEnum;
@@ -47,6 +51,16 @@ public class JRVerticalFiller extends JRBaseFiller
 
 	private static final Log log = LogFactory.getLog(JRVerticalFiller.class);
 
+	// Whether we are configured to fill the detail section with blank rows of data.
+	// Is configured to not fill by default.
+	private boolean fillDetailWithBlankRows = false;
+
+	// Flag to indicate whether we've reached the end of our main data set.
+	private boolean isEndOfMainDataset = false;
+
+	// Flag to indicate when we're writing the detail section.
+	private boolean writingDetailSection = false;
+
 	/**
 	 *
 	 */
@@ -81,6 +95,26 @@ public JRVerticalFiller(
 		setPageHeight(pageHeight);
 	}
 
+	@Override
+	protected void setParameters(Map<String, Object> parameterValues) throws JRException
+	{
+	  super.setParameters(parameterValues);
+
+	  setFillDetailWithBlankRows(parameterValues);
+	}
+
+	protected void setFillDetailWithBlankRows(Map<String,Object> parameterValues)
+	{
+		Object value = parameterValues.getOrDefault(JRParameter.REPORT_FILL_DETAIL_WITH_BLANK_ROWS, Boolean.FALSE);
+		if (value instanceof String)
+		{
+			fillDetailWithBlankRows = Boolean.parseBoolean((String)value);
+		} else if (value instanceof Boolean)
+		{
+			fillDetailWithBlankRows = ((Boolean)value).booleanValue();
+		}
+	}
+
 
 	@Override
 	protected void setPageHeight(int pageHeight)
@@ -98,6 +132,15 @@ protected void setPageHeight(int pageHeight)
 		}
 	}
 
+	/**
+	 * {@inheritDoc}
+	 */
+	@Override
+	public JasperPrint fill(Map<String, Object> parameterValues) throws JRException
+	{
+		isEndOfMainDataset = false;
+		return super.fill(parameterValues);
+	}
 
 	@Override
 	@continuable
@@ -231,7 +274,42 @@ protected synchronized void fillReport() throws JRException
 		}
 	}
 
+	/**
+	 * {@inheritDoc}
+	 */
+	@Override
+	protected boolean next() throws JRException {
+		if (super.next()) {
+			return true;
+		}
+		if (fillDetailWithBlankRows) {
+			// If we have no more data in our main data set and we are configured to fill will blank rows,
+			// move the cursor forward until we have reached the end of the current page's detail section.
+			isEndOfMainDataset = true;
+			return !endOfPageDetail();
+		}
+		return false;
+	}
+
+	private boolean endOfPageDetail() {
+		JRFillBand[] detailBands = detailSection.getFillBands();
+		for (int i = 0; i < detailBands.length; i++) {
+			JRFillBand detailBand = detailBands[i];
+			if (detailBand.isToPrint() && (detailBand.getBreakHeight() > columnFooterOffsetY - offsetY)) {
+				return true;
+			}
+		}
+		return false;
+	}
 
+	/**
+	 * {@inheritDoc}
+	 */
+	@Override
+	protected boolean evaluateElementToBlank() {
+		return isEndOfMainDataset && writingDetailSection;
+	}
+
 	/**
 	 *
 	 */
@@ -752,6 +830,8 @@ private void fillGroupHeaderReprint(JRFillGroup group, byte evaluation) throws J
 	@continuable
 	private void fillDetail() throws JRException
 	{
+		writingDetailSection = true;
+
 		if (log.isDebugEnabled() && !detailSection.isEmpty())
 		{
 			log.debug("Fill " + fillerId + ": detail at " + offsetY);
@@ -851,6 +931,7 @@ private void fillDetail() throws JRException
 
 		isNewPage = false;
 		isNewColumn = false;
+		writingDetailSection = false;
 	}
 
 

jasperreports/tests/net/sf/jasperreports/AbstractTest.java

@@ -38,12 +38,14 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
 import java.util.TimeZone;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.testng.annotations.BeforeClass;
 
+import net.sf.jasperreports.engine.JRDataSource;
 import net.sf.jasperreports.engine.JRException;
 import net.sf.jasperreports.engine.JRParameter;
 import net.sf.jasperreports.engine.JasperCompileManager;
@@ -103,16 +105,26 @@ protected void runReport(String jrxmlFileName, String referenceFileNamePrefix)
 		HashMap<String, Object> params = new HashMap<String, Object>();
 		params.put(JRParameter.REPORT_LOCALE, Locale.US);
 		params.put(JRParameter.REPORT_TIME_ZONE, TimeZone.getTimeZone("GMT"));
+		params.putAll(additionalReportParams());
 		params.put(TEST, this);
 
+		JRDataSource dataSource = createDataSource();
+
 		log.debug("Running report " + jrxmlFileName);
 
 		try
 		{
 			JasperReport report = compileReport(jrxmlFileName);
 			if (report != null)
 			{
-				JasperPrint print = fillManager.fill(report, params);
+				JasperPrint print;
+				if (dataSource == null)
+				{
+					print = fillManager.fill(report, params);
+				} else
+				{
+					print = fillManager.fill(report, params, dataSource);
+				}
 
 				assert !print.getPages().isEmpty();
 
@@ -154,6 +166,14 @@ protected void runReport(String jrxmlFileName, String referenceFileNamePrefix)
 		}
 	}
 
+	protected Map<String, Object> additionalReportParams() {
+		return new HashMap<>();
+	}
+
+	protected JRDataSource createDataSource() {
+		return null;
+	}
+
 	protected JasperReportsContext getJasperReportsContext()
 	{
 		return jasperReportsContext;

jasperreports/tests/net/sf/jasperreports/bands/fill/BandFillTest.java

@@ -0,0 +1,94 @@
+/*
+ * JasperReports - Free Java Reporting Library.
+ * Copyright (C) 2001 - 2019 TIBCO Software Inc. All rights reserved.
+ * http://www.jaspersoft.com
+ *
+ * Unless you have purchased a commercial license agreement from Jaspersoft,
+ * the following license terms apply:
+ *
+ * This program is part of JasperReports.
+ *
+ * JasperReports is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * JasperReports is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with JasperReports. If not, see <http://www.gnu.org/licenses/>.
+ */
+package net.sf.jasperreports.bands.fill;
+
+import java.io.IOException;
+import java.security.NoSuchAlgorithmException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.stream.IntStream;
+
+import org.testng.annotations.DataProvider;
+import org.testng.annotations.Test;
+
+import net.sf.jasperreports.AbstractTest;
+import net.sf.jasperreports.engine.JRDataSource;
+import net.sf.jasperreports.engine.JRException;
+import net.sf.jasperreports.engine.JRParameter;
+import net.sf.jasperreports.engine.data.JRBeanArrayDataSource;
+
+/** @author Tim Hewson */
+public class BandFillTest extends AbstractTest
+{
+
+	@Override
+	protected Map<String, Object> additionalReportParams()
+	{
+		Map<String, Object> params = new HashMap<String, Object>();
+		params.put(JRParameter.REPORT_FILL_DETAIL_WITH_BLANK_ROWS, Boolean.TRUE);
+		return params;
+	}
+
+
+	@Override
+	protected JRDataSource createDataSource()
+	{
+		return new JRBeanArrayDataSource(
+				IntStream.range(0, 90)
+				.mapToObj(i -> new Ascii(33 + i, String.valueOf((char) (33 + i))))
+				.toArray());
+	}
+
+	@Test(dataProvider = "testArgs")
+	public void testReport(String jrxmlFileName, String referenceFileNamePrefix) 
+			throws JRException, NoSuchAlgorithmException, IOException
+	{
+		runReport(jrxmlFileName, referenceFileNamePrefix);
+	}
+
+	@DataProvider
+	public Object[][] testArgs()
+	{
+		return runReportArgs("net/sf/jasperreports/bands/fill/repo", "BandFillReport", 40);
+	}
+
+	public static class Ascii
+	{
+		long record_num;
+		String record_val;
+
+		Ascii(long number, String value) {
+			this.record_num = number;
+			this.record_val = value;
+		}
+
+		public long getRecord_num() {
+			return record_num;
+		}
+
+		public String getRecord_val() {
+			return record_val;
+		}
+	}
+}