Creating PDF with nFOP

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Introduction

nFOP is an elegant solution to generate PDF on the fly. It is originally a Java open source product that has been migrated to .NET.

The purpose of this article is to show the use of nFOP to generate a PDF file from XML data. We won't describe the FO format here. Many excellent articles exist on the Web about FO which is a W3C standard. Unfortunately it doesn't seem to be much known by the .NET community so far.

First, you have to download nFOP from here.

Using the Code

Here is the data in input - my favourite French books:

Books.xml

<?xml version="1.0" encoding="utf-8" ?>
<Books>
  <Book>
    <Title>Madame Bovary</Title>
    <Author>Gustave Flaubert</Author>
    <Price>10</Price>
  </Book>
  <Book>
    <Title>Bel Ami</Title>
    <Author>Maupassant</Author>
    <Price>18</Price>
  </Book>
  <Book>
    <Title>La Curée</Title>
    <Author>Emile Zola</Author>
    <Price>12</Price>
  </Book>
  <Book>
    <Title>Les Chouans</Title>
    <Author>Honoré de Balzac</Author>
    <Price>15</Price>
  </Book>
</Books>

Here is now the XSL transformation that I will apply to this XML. I create a table in FO language, with three columns. The rows will be generated by the XSL transformation, one for each book.

BookFo.xsl

<fo:table-body>
      <fo:table-row>
        <fo:table-cell>
          <fo:block>Title</fo:block>
        </fo:table-cell>
        <fo:table-cell>
          <fo:block>Author</fo:block>
        </fo:table-cell>
        <fo:table-cell>
          <fo:block>Price</fo:block>
        </fo:table-cell>
      </fo:table-row>
      <xsl:for-each select="Books/Book">
        <fo:table-row>
          <fo:table-cell>
            <fo:block>
              <xsl:value-of select=".//Title" />
            </fo:block>
          </fo:table-cell>
          <fo:table-cell>
            <fo:block>
              <xsl:value-of select=".//Author" />
            </fo:block>
          </fo:table-cell>
          <fo:table-cell>
            <fo:block>
              <xsl:value-of select=".//Price" />
            </fo:block>
          </fo:table-cell>
        </fo:table-row>
      </xsl:for-each>
    </fo:table-body>
  </fo:table>

In Visual Studio, reference the nFop assembly ApacheFop.Net.dll and the J# assembly vjslib.dll.

You will need to add the following namespaces to your class:

    using System.Xml;
    using System.Xml.Xsl;
    using System.Xml.XPath;
    using org.apache.fop;
    using org.apache.fop.apps;
    using org.apache.fop.tools;
    using org.xml.sax;
    using java.io;

We call the classic XML/XSL transformation to produce the FO file:

    // Load the FO style sheet.
    XslCompiledTransform xslt = new XslCompiledTransform();
    xslt.Load("bookFo.xsl");

    // Execute the transform and output the results to a file.
    xslt.Transform("books.xml", "books.fo");

At last, here comes the most interesting part, the use of NFOP to generate the PDF file.

Here is the method that does the job:

    private void GeneratePDF(string foFile, string pdfFile)
    {
        FileInputStream streamFO = new FileInputStream(foFile);
        InputSource src = new InputSource(streamFO);
        FileOutputStream streamOut = new FileOutputStream(pdfFile);
        Driver driver = new Driver(src, streamOut);
        driver.setRenderer(1);
        driver.run();
        streamOut.close();
    }

Conclusion

nFOP is an easy solution to implement and it is free. Because the PDF structure is described in an XML file, it is easy to configure its disposition, which clients always ask for.

To learn more about FOP, visit the Apache site and download the Java version. It contains plenty of samples of FO files and good documentation.