Sams Teach Yourself XML in 21 Days

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Sams Teach Yourself XML in 21 Days, 3rd Edition

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Recommended Book

Recommended Book 

Sams Teach Yourself XML in 21 Days, 3rd Edition

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Using XSL-FO

You've already seen a short XSL-FO example, but in fact, XML documents are only rarely formatted by directly using formatting objects as in the example you've seen because the process becomes too complex. What usually happens is that you take an XML document (with the extension .xml), run it through an XSLT processor to create a new XML document that uses XSL-FO (with the extension .fo), and then use an XSL-FO processor to create the formatted display document (with the extension .pdf in today's discussion). You do things this way because any document except a nontrivial one has many paragraphs of text or data, and to format each one by hand would be a time-consuming process.

In fact, XSLT was originally developed for formatting XML documents by using XSL-FO objects. Since then, being able to access XML data without writing software using XSLT in itself has become so powerful that XSLT has outstripped XSL-FO in popularity.

For example, say that you want to use XSL-FO to format the XML document with state data that you worked with yesterday. Let's use that document today, renaming it ch10_01.xml, as shown in Listing 10.1.

Example 10.1. An Example of an XML Document (ch10_01.xml)

<?xml version="1.0" encoding ="UTF-8"?>
<states>

    <state>
        <name>California</name>
        <population units="people">33871648</population><!--2000 census-->
        <capital>Sacramento</capital>
        <bird>Quail</bird>
        <flower>Golden Poppy</flower>
        <area units="square miles">155959</area>
    </state>

    <state>
        <name>Massachusetts</name>
        <population units="people">6349097</population><!--2000 census-->
        <capital>Boston</capital>
        <bird>Chickadee</bird>
        <flower>Mayflower</flower>
        <area units="square miles">7840</area>
    </state>

    <state>
        <name>New York</name>
        <population units="people">18976457</population><!--2000 census-->
        <capital>Albany</capital>
        <bird>Bluebird</bird>
        <flower>Rose</flower>
        <area units="square miles">47214</area>
    </state>

</states>

As you'll see later today, the XSL-FO document holding this data that you're going to feed into an XSL-FO processor is about three times the length of ch10_01.xml, which is why it makes sense to use XSLT to convert ch10_01.xml into a document that uses XSL-FO. Let's take a look at the XSLT style sheet that will do that.

Using XSLT to Create an XSL-FO Document

Although you could format ch10_01.xml by hand, it's easier to use an XSLT style sheet to do so. Listing 10.2 contains the style sheet (ch10_02.xml) that you're going to use in this example. In this case, you're just going to extract the state data from ch10_01.xml and present that data in a list form, using 18-point font.

Example 10.2. An XSL Document That Adds XSL-FO Formatting (ch10_02.xsl)

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:fo="http://www.w3.org/1999/XSL/Format"
    version='1.0'>

    <xsl:template match="states">
        <fo:root>

            <fo:layout-master-set>
                 <fo:simple-page-master master-name="mainPage"
                     page-height="300mm" page-width="200mm"
                     margin-top="20mm" margin-bottom="20mm"
                     margin-left="20mm" margin-right="20mm">

                     <fo:region-body
                       margin-top="0mm" margin-bottom="10mm"
                       margin-left="0mm" margin-right="0mm"/>

                     <fo:region-after extent="20mm"/>
                 </fo:simple-page-master>
             </fo:layout-master-set>

             <fo:page-sequence master-reference="mainPage">
                 <fo:flow  flow-name="xsl-region-body">
                     <xsl:apply-templates/>
                 </fo:flow>
             </fo:page-sequence>

        </fo:root>
    </xsl:template>

    <xsl:template match="state/name">
        <fo:block font-weight="bold" font-size="18pt"
            line-height="24pt" font-family="sans-serif"
            text-decoration="underline">
            Name:
            <xsl:value-of select="."/>
        </fo:block>
    </xsl:template>

    <xsl:template match="state/population">
        <fo:block font-size="18pt" line-height="24pt"
            font-family="sans-serif">
            Population (people):
            <xsl:value-of select="."/>
        </fo:block>
    </xsl:template>

    <xsl:template match="state/capital">
        <fo:block font-size="18pt" line-height="24pt" font-family="sans-serif">
            Capital:
            <xsl:value-of select="."/>
        </fo:block>
    </xsl:template>

    <xsl:template match="state/bird">
        <fo:block font-size="18pt" line-height="24pt" font-family="sans-serif">
            Bird:
            <xsl:value-of select="."/>
        </fo:block>
    </xsl:template>

    <xsl:template match="state/flower">
        <fo:block font-size="18pt" line-height="24pt" font-family="sans-serif">
            Flower:
            <xsl:value-of select="."/>
        </fo:block>
    </xsl:template>

    <xsl:template match="state/area">
        <fo:block font-size="18pt" line-height="24pt" font-family="sans-serif">
            Area (square miles):
            <xsl:value-of select="."/>
        </fo:block>
    </xsl:template>

</xsl:stylesheet>

Today you'll see how ch10_02.xsl works and what it does. The first step, as described in the following section, is to put this style sheet to work and create the XSL-FO document.

Creating an XSL-FO Document by Using an XSLT Style Sheet

You're ready to create an XSL-FO document, which you can call ch10_03.fo. This document is the one you'll feed into an XSL-FO processor to create a formatted PDF document that will display the data from the XML document ch10_01.xml. To create ch10_03.fo, you only need to apply the XSLT style sheet ch10_02.xsl to the XML document ch10_01.xml. For example, if you have Java 1.4 or later installed, you can use the Java file ch09_05.class that is in the code download area for this book that you used yesterday, like this:

%java ch09_05 ch10_01.xml ch10_02.xsl ch10_03.fo

This creates ch10_03.fo, which is ch10_01.xml formatted with XSL-FO. Listing 10.3 presents ch10_03.fo; note the length of it compared to the original XML document, ch10_01.xml, and you can see why it's a good idea to use XSLT to create XSL-FO documents if you're working with data of any significant length.

Example 10.3. An XSL-FO Document (ch10_03.fo)

<?xml version="1.0" encoding="UTF-8"?>
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
    <fo:layout-master-set>
        <fo:simple-page-master margin-right="20mm"
            margin-left="20mm" margin-bottom="20mm" margin-top="20mm"
            page-width="200mm" page-height="300mm" master-name="mainPage">
            <fo:region-body margin-right="0mm" margin-left="0mm"
                margin-bottom="10mm" margin-top="0mm"/>
            <fo:region-after extent="20mm"/>
        </fo:simple-page-master>
    </fo:layout-master-set>

    <fo:page-sequence master-reference="mainPage">
        <fo:flow flow-name="xsl-region-body">

            <fo:block text-decoration="underline" font-family="sans-serif"
                line-height="24pt" font-size="18pt" font-weight="bold">
                Name:
                California
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Population (people):
                33871648
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Capital:
                Sacramento
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Bird:
                Quail
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Flower:
                Golden Poppy
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Area (square miles) :
                155959
            </fo:block>

            <fo:block text-decoration="underline" font-family="sans-serif"
                line-height="24pt" font-size="18pt" font-weight="bold">
                Name:
                Massachusetts
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Population (people):
                6349097
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Capital:
                Boston
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Bird:
                Chickadee
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Flower:
                Mayflower
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Area (square miles):
                7840
            </fo:block>

            <fo:block text-decoration="underline" font-family="sans-serif"
                line-height="24pt" font-size="18pt" font-weight="bold">
                Name:
                New York
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Population (people):
                18976457
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Capital:
                Albany
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Bird:
                Bluebird
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Flower:
                Rose
            </fo:block>
            <fo:block font-family="sans-serif" line-height="24pt"
                font-size="18pt">
                Area (square miles):
                47214
            </fo:block>

        </fo:flow>
    </fo:page-sequence>
</fo:root>

You now have ch10_03.fo, which is ready to feed into an XSL-FO processor.

Creating a PDF Document

To use ch10_03.fo and convert it into a PDF file, ch10_04.pdf, you can use what is probably the most popular XSL-FO processor, the Apache XML Project's FOP. You can get FOP for free at http://xml.apache.org/fop; just click the Download button. The current version as of this writing is 0.20.4 (0.20.5 is available in a release candidate version, but it's not yet official), and it's written in Java, which means you have to have Java installed in order to use it. The compressed file you download is fop-0.20.4-bin.tar.gz. (.tar.gz files are targeted to Unix, but Windows unzip utilities, such as WinZip, from http://www.winzip.com, can unzip them as well.)

Here's how to use FOP to convert ch10_03.fo into ch10_04.pdf, assuming that ch10_03.fo is in the same directory where you unzipped FOP (the -cp switch here sets the Java classpath variable, which you'll discuss further on Day 16, "Using Java and .NET: DOM"):

%java -cp build\fop.jar;lib\batik.jar;lib\xalan-2.3.1.jar;
lib\xercesImpl-2.0.1.jar;lib\xml-apis.jar;
lib\avalon-framework-cvs-20020315.jar;lib\logkit-1.0.jar;
lib\jimi-1.0.jar org.apache.fop.apps.Fop ch10_03.fo ch10_04.pdf

This is not very easy to type, so FOP also supplies shell scripts for most shells, including a .bat file for Windows, which means that the following is usually all you have to type:

%fop ch10_03.fo ch10_04.pdf

This creates ch10_04.pdf, which is the goal you've been working toward. To view this PDF document, you can use the Adobe Acrobat PDF viewer, which you can download for free from Adobe at http://www.adobe.com (currently, Adobe Acrobat reader is available at http://www.adobe.com/products/acrobat/readermain.html). Figure 10.1 shows ch10_04.pdf in Adobe Acrobat. As you can see in the figure, the data from the XML document has indeed been formatted into a PDF document.

Figure 10.1 Formatting XML data in PDF format.

Now take a look at how to create your own XSL-FO formatting.