How to create XSL-FO (.fo) file in Spring Boot and convert it to PDF (Part 1)

In this article, I will show you how to create an XSL-FO (.fo) file (in Spring boot) and how to convert it to a PDF

Overview

An XSL-FO file can be written using .xsl and .fo extensions. Today, we will create an XSL-FO file using the .fo extension. This file is used to convert data written with specific template rules into a PDF.

Let’s start doing that now…

Create .fo file

Under the “resources” folder, create a new file by selecting “New” and naming it with the “.fo” extension.

create a new directory (optional)

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
    <!-- Layout master set definition -->
    <fo:layout-master-set>
        <fo:simple-page-master master-name="simple">
            <fo:region-body margin="1in"/>
        </fo:simple-page-master>
    </fo:layout-master-set>

    <!-- Page sequence using the simple master layout -->
    <fo:page-sequence master-reference="simple">
        <fo:flow flow-name="xsl-region-body">
            <!-- Block containing inline styled text -->
            <fo:block>
                <fo:inline font-weight="bold">Text</fo:inline>
                <fo:inline font-style="italic">Text2</fo:inline>
            </fo:block>
            <!-- Table with two columns and one row -->
            <fo:table border="0.5pt solid black" table-layout="fixed" width="100%">
                <fo:table-column column-width="50%"/>
                <fo:table-column column-width="50%"/>
                <fo:table-body>
                    <fo:table-row>
                        <fo:table-cell border="0.5pt solid black" padding="5pt">
                            <fo:block>Cell1</fo:block>
                        </fo:table-cell>
                        <fo:table-cell border="0.5pt solid black" padding="5pt">
                            <fo:block>Cell2</fo:block>
                        </fo:table-cell>
                    </fo:table-row>
                </fo:table-body>
            </fo:table>
        </fo:flow>
    </fo:page-sequence>
</fo:root>

Note!

Here, the file extension (.fo or .xsl) doesn’t make a difference in Spring Boot usage. I’ve tested this — you can use either. The real difference lies in their content, which you’ll see in the next part. XSL-FO files are divided into 2 different content.

• Full XSL-FO Document
• XSLT-based Transformation and Styling

Don’t worry, I will talk about these in upcoming sections. Let’s continue with this for now.

How to convert a .fo file to PDF.

First, we need a library for the conversion process (Apache FOP).
Ok. Good question. What is Apache FOP?

Apache FOP

Apache FOP (Formatting Objects Processor) is an open-source Java library for generating PDF and other output formats from XML documents. FOP processes XSL-FO (Extensible Stylesheet Language Formatting Objects) documents and converts them into different formats such as PDF, PostScript, PCL, AFP, SVG, XML (Areas Tree representation), and Print.

for gradle

implementation 'org.apache.xmlgraphics:fop:2.8'

for maven

<dependency>
    <groupId>org.apache.xmlgraphics</groupId>
    <artifactId>fop</artifactId>
    <version>2.8</version>
</dependency>

You can use Apache FOP to convert XSL-FO to PDF. The following code snippet converts the previously generated .fo file to PDF.

import lombok.SneakyThrows;
import org.apache.fop.apps.Fop;
import org.apache.fop.apps.FopFactory;
import org.apache.fop.apps.MimeConstants;

import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.sax.SAXResult;
import javax.xml.transform.stream.StreamSource;
import java.io.File;
import java.io.FileOutputStream;

public class FoFileToPdf {

    @SneakyThrows
    public static void main(String[] args) {
        File xsltFile = new File("src/main/resources/files/doc.fo");
        String desktopPath = System.getProperty("user.home") + File.separator + "Desktop";
        File desktopDir = new File(desktopPath);

        if (!desktopDir.exists()) {
            desktopDir.mkdirs();
        }

        File pdfFile = new File(desktopDir, "test.pdf");
        FopFactory fopFactory = FopFactory.newInstance(new File(".").toURI());
        Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, new FileOutputStream(pdfFile));
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        transformer.transform(new StreamSource(xsltFile), new SAXResult(fop.getDefaultHandler()));
    }
}

And that’s it, now you have converted your .fo file to PDF. You can write any content you want inside the .fo file.

GitHub

Part 2 — PDF generate as dynamically