[Not able to generate a bar chart]

Hi ,

I am new to Jasper Reports and i am trying to generate a bar chart with data coming from my data source but am getting stuck at a place. I am getting exception which i am not able to resolve. Cant figure out where am i going wrong . Can someone pls help.

Exception in thread "main" java.lang.NullPointerException at net.sf.jasperreports.charts.fill.JRFillCategoryDataset.customIncrement(JRFillCategoryDataset.java:136) at net.sf.jasperreports.engine.fill.JRFillElementDataset.increment(JRFillElementDataset.java:134)

Heres the java file.

 

public class JasperReportsIntro

{

public static void main(String[] args)

{

JasperReport jasperReport;

JasperPrint jasperPrint;

try

{

jasperReport = JasperCompileManager.compileReport("/home/arpana/work/bccms/src/com/bc/reports/rep/jasperreports_demo.jrxml");

String columnNames[]={"FIELD1","VALUE"};

ArrayList arrayList = new ArrayList<ArrayList<Double>>();

List<Double> dataArray = new ArrayList<Double>();

dataArray.add(0.0);

dataArray.add(1.0);

 

arrayList.add(dataArray);

 

List<Double> dataArray1 = new ArrayList<Double>();

dataArray1.add(2.0);

dataArray1.add(3.0);

arrayList.add(dataArray1);

 

jasperPrint = JasperFillManager.fillReport(jasperReport, new HashMap(), new JRTableModelDataSource(new DataSource(columnNames, arrayList)));

JasperExportManager.exportReportToPdfFile(jasperPrint, "/home/arpana/bar_report.pdf");

System.out.println("Successfully exported to PDF");

}

catch (JRException e)

{

e.printStackTrace();

}

}

}

 

Heres the jrxml file :

<?xml version="1.0"?>

<!DOCTYPE jasperReport

PUBLIC "-//JasperReports//DTD Report Design//EN"

"http://jasperreports.sourceforge.net/dtds/jasperreport.dtd">

 

<jasperReport name="Simple_Report">

 

<parameter name="VALUE_HEADER_P" isForPrompting="false" class="java.lang.String"/>

 

<field name="FIELD1" class="java.lang.Double">

</field>

<field name="VALUE" class="java.lang.Double">

</field>

 

<variable name="SumFirstGroup" class="java.lang.Double">

<variableExpression><![CDATA[$F{VALUE}]]></variableExpression>

</variable>

 

<group name="FirstGroup" isStartNewColumn="false" isReprintHeaderOnEachPage="false" minHeightToStartNewPage="25">

<groupExpression><![CDATA[$F{FIELD1}]]></groupExpression>

</group>

 

<detail>

<band height="120">

<staticText>

<reportElement x="80" y="0" width="200" height="20"/>

<text><![CDATA[Hello World!]]></text>

</staticText>

<barChart>

<chart evaluationTime="Report">

<reportElement positionType="Float" x="0" y="35" width="540" height="75"/>

</chart>

<categoryDataset>

<dataset incrementType="Group" incrementGroup="FirstGroup"/>

<categorySeries>

<seriesExpression>$P{VALUE_HEADER_P}</seriesExpression>

<categoryExpression>$F{FIELD1}</categoryExpression>

<valueExpression>new Double($F{VALUE}.doubleValue() / 2d)</valueExpression>

</categorySeries>

</categoryDataset>

<barPlot isShowTickMarks="true" isShowTickLabels="true">

<plot/>

</barPlot>

</barChart>

</band>

</detail>

</jasperReport>

 

And finally the data source file.

public class DataSource extends AbstractTableModel

{

 

private String[] columnNames = null;;

private String[] columnDisplayNames = null;

 

/**

* ArrayList of ArrayLists

*/

private ArrayList<ArrayList> data = null;

 

public DataSource(String[] columns, ArrayList records)

{

columnNames = columns;

data = records;

}

 

public void setColumnDisplayNames(String[] displayNames)

{

columnDisplayNames = displayNames;

}

 

public String[] getColumnDisplayNames()

{

return columnDisplayNames;

}

 

public int getColumnCount()

{

return this.columnNames.length;

}

 

public String getColumnName(int columnIndex)

{

return this.columnNames[columnIndex];

}

 

public int getRowCount()

{

return this.data.size();

}

 

public Object getValueAt(int rowIndex, int columnIndex)

{

ArrayList record = (ArrayList) data.get(rowIndex);

return record.get(columnIndex);

}

 

public ArrayList getData()

{

return data;

}

 

}