Inspired by Jarvis and mostly for fun
As you have correctly noted you can't render html table in textField you would need to use the HtmlComponent <hc:html/> but this will create an image and you will not only have scaling problems but also issue as selection and searchability of text. Furthermore as Dave Jarvis has stated in their answer this in general is not a suitable way to pass data to jasper reports.
But who cares about all that lets render your html
We need to convert the html to a JRDataSource, we will do this using Jsoup
public class HtmlTableDataSource implements JRDataSource {
private List<Elements> rows;
private Iterator<Elements> iterator;
private Elements currentRow;
public HtmlTableDataSource(String html) {
super();
init(html);
}
private void init(String html) {
this.rows = new ArrayList<>();
Document doc = Jsoup.parse(html);
Elements tables = doc.select("table");
if (tables == null || tables.isEmpty()) {
return;
}
// Get first table ignore others
Element table = tables.get(0);
//Get all rows
Elements trs = table.select("tr");
for (Element element : trs) {
//add all of our columns to our list
this.rows.add(element.select("td"));
}
this.iterator = this.rows.iterator();
}
@Override
public Object getFieldValue(JRField field) throws JRException {
if (field==null||currentRow==null){
return null;
}
try {
int col = Integer.parseInt(field.getName());
if (col<currentRow.size()){
return currentRow.get(col).html();
}
} catch (NumberFormatException e) {
throw new JRException("Using the HTMLTableDataSource, the field name need to be numbers starting from 0");
}
return null;
}
@Override
public boolean next() throws JRException {
if (this.iterator == null || !this.iterator.hasNext()) {
return false;
}
this.currentRow = this.iterator.next();
return true;
}
}
Now lets use it in a report (you need the above class and Jsoup in classpath)
<?xml version="1.0" encoding="UTF-8"?>
<jasperReport xmlns="http://jasperreports.sourceforge.net/jasperreports" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports http://jasperreports.sourceforge.net/xsd/jasperreport.xsd" name="htmlTable" pageWidth="595" pageHeight="842" whenNoDataType="AllSectionsNoDetail" columnWidth="555" leftMargin="20" rightMargin="20" topMargin="20" bottomMargin="20" uuid="597c0716-df6b-42ec-a7c8-863eb1b7174a">
<style name="Table_TD" mode="Opaque" backcolor="#FFFFFF">
<box>
<pen lineWidth="0.5" lineColor="#000000"/>
<topPen lineWidth="0.5" lineColor="#000000"/>
<leftPen lineWidth="0.5" lineColor="#000000"/>
<bottomPen lineWidth="0.5" lineColor="#000000"/>
<rightPen lineWidth="0.5" lineColor="#000000"/>
</box>
</style>
<subDataset name="TableDataset" uuid="998ba41a-db15-454b-a081-bc8613899c31">
<field name="0" class="java.lang.String"/>
<field name="1" class="java.lang.String"/>
</subDataset>
<summary>
<band height="30">
<componentElement>
<reportElement x="0" y="0" width="550" height="30" uuid="5d0d5bcb-a094-4446-a5e9-09de629cefc7"/>
<jr:table xmlns:jr="http://jasperreports.sourceforge.net/jasperreports/components" xsi:schemaLocation="http://jasperreports.sourceforge.net/jasperreports/components http://jasperreports.sourceforge.net/xsd/components.xsd">
<datasetRun subDataset="TableDataset" uuid="eac86c28-fad2-433a-a02e-0dd419d9e135">
<dataSourceExpression><![CDATA[new my.package.HtmlTableDataSource("<table style='border: 1px solid black'><tr><td style='border: 1px solid black'><b>1</b></td><td style='border: 1px solid black'><b>2</b></td></tr><tr><td style='border: 1px solid black'>Data</td><td style='border: 1px solid black'>Data</td></tr></table>")]]></dataSourceExpression>
</datasetRun>
<jr:column width="180" uuid="86ce5c9c-d285-4a51-bf84-30fa9c55579f">
<jr:detailCell style="Table_TD" height="30">
<textField>
<reportElement x="0" y="0" width="180" height="30" uuid="3acb437b-8b59-4e78-ac1b-4f096f960e89"/>
<textElement textAlignment="Center" verticalAlignment="Middle" markup="html"/>
<textFieldExpression><![CDATA[$F{0}]]></textFieldExpression>
</textField>
</jr:detailCell>
</jr:column>
<jr:column width="150" uuid="741517bf-5107-4b13-9d61-44209f266c6c">
<jr:detailCell style="Table_TD" height="30">
<textField>
<reportElement x="0" y="0" width="150" height="30" uuid="1174a60c-8b9e-441b-a9ef-4340b0cd7b68"/>
<textElement textAlignment="Center" verticalAlignment="Middle" markup="html"/>
<textFieldExpression><![CDATA[$F{1}]]></textFieldExpression>
</textField>
</jr:detailCell>
</jr:column>
</jr:table>
</componentElement>
</band>
</summary>
</jasperReport>
The <dataSourceExpression><![CDATA[new my.package.HtmlTableDataSource("<table..")]]></dataSourceExpression> this will instance our datasource and jasper reports will loop over it calling the next() method and the getFieldValue(JRField field) when field is to be evaluate
Result
Other considerations
My implementation of the JRDataSource is just quick and fun, naturally it can be vastly improved.
Dynamic columns, if only a maximum number and they are fixed size you could use a solution similar to this https://stackoverflow.com/a/36911788/5292302 if not switch to use crosstabs modifying the JRDataSource as needed.
Yes I changed <strong/> to <b/> this is another problem Why does html tags (s, strong) not work in jasper reports?, in this case you could also handle it within your datasource, hence use Jsoup to substitute.
