Hack 85 Syndicate a List of Books with RSS

Someday all data will be available as RSS. Get a head start by syndicating Amazon search results.

RSS is an XML format that's widely used to syndicate content. Depending on who you ask, it stands for Rich Site Summary or Really Simple Syndication and has become a standard way for publishers to make their content available. News Readers are programs that gather RSS feeds together and transform them into human-readable form. They've become a popular way to read news sites online.

With the wide audience for RSS data, just about everything is being turned into an RSS feed. This hack by Sean Nolan turns any AWS query result into an RSS feed.

85.1 What You Need

This hack uses ASP, which runs on Windows servers running IIS. The logic is straightforward, though, and could be translated to any scripting language.

85.2 The Code

Create a file called amazon_rss.asp and include the following code. Be sure to change the Const declarations to match your setup.

<%
'' AMAZON-RSS.ASP
'' Sean P. Nolan
'' http://www.yaywastaken.com/
''
'' This code is free for you to use as you see fit. Copy it, rewrite it, 
'' run it yourself, whatever. But no warranties or guarantees either. Who
'' knows what the hell it does. Not me, that's for sure!
''
'' Generates an RSS 0.91 feed from an Amazon book query
''
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    Const MAX_PAGES_DEFAULT = 10
    Const DEV_TOKEN = "insert developer token"
    Const AFFILIATE_CODE = "insert associate tag"
    Const XSL_FILE = "amazon_lite.xsl" 'change to heavy for more info.

    Dim szTitle, szMaxPages, nMaxPages

    Response.ContentType = "text/xml"
    Server.ScriptTimeout = 60 * 4 ' 4-minute maximum
    Response.Expires = 0

    szMaxPages = Request.QueryString("maxpages")
    If (szMaxPages = "") Then
        nMaxPages = MAX_PAGES_DEFAULT
    Else
        nMaxPages = CLng(szMaxPages)
    End If

    szTitle = "Amazon Books: " & XMLify(Request.QueryString("keywords"))

    %><?xml version="1.0" encoding="ISO-8859-1" ?>
<rss version="0.91">
    <channel>
        <link>http://www.yaywastaken.com/amazon/</link>
        <title><%= szTitle %></title>
        <description>Create your own custom Amazon RSS feed!</description>
        <language>en-us</language>
<% 
RenderItems Request.QueryString("keywords"), _
            Request.QueryString("browse") , _
            Request.QueryString("author") , _
            Request.QueryString("shortdesc"), _
            nMaxPages
%>

    </channel>
</rss>
    <%

    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    ' RenderItems

    Sub RenderItems(szKeywords, szBrowseNode, szAuthor, szShortDesc, [RETURN]
nMaxPages)
        Dim szURLFmt, szURL, xmlDoc, ipage, http, xmlErr
        Dim fParsed, xslDoc, szXSLPath, szOutput

        'On Error Resume Next

        If (szShortDesc <> "") Then
            szXSLPath = "amazon-lite.xsl"
        Else
            szXSLPath = "amazon-heavy.xsl"
        End If

        Set xslDoc = Server.CreateObject("Msxml2.DOMDocument")
        xslDoc.async = False
        xslDoc.load(Server.MapPath(szXSLPath))

        If (szBrowseNode <> "") Then
            szURLFmt = "http://xml.amazon.com/onca/xml?v=1.0&" & _
                       "t=" & AFFILIATE_CODE & _
                          "&dev-t=" & DEV_TOKEN & "&BrowseNodeSearch=" & _
                          Server.URLEncode(szBrowseNode) & _
                          "&mode=books&type=heavy&page=%%%PAGE%%%&f=xml"
        ElseIf (szAuthor <> "") Then
            szURLFmt = "http://xml.amazon.com/onca/xml?v=1.0&" & _
                       "t=" & AFFILIATE_CODE & _
                          "&dev-t=" & DEV_TOKEN & "&AuthorSearch=" & _
                          Server.URLEncode(szAuthor) & _
                          "&mode=books&type=heavy&page=%%%PAGE%%%&f=xml"
        Else
            szURLFmt = "http://xml.amazon.com/onca/xml?v=1.0&" & _
                       "t=" & AFFILIATE_CODE & _
                          "&dev-t=" & DEV_TOKEN & "&KeywordSearch=" & _
                          Server.URLEncode(szKeywords) & _
                          "&mode=books&type=heavy&page=%%%PAGE%%%&f=xml"
        End If

        ipage = 1
        Do
            szURL = Replace(szURLFmt, "%%%PAGE%%%", ipage)

            Set http = Server.CreateObject("Msxml2.ServerXMLHTTP")
            http.open "GET", szURL, False
            http.send ""

            If (http.status <> 200) Then
                Exit Do
            End If

            Set xmlDoc = Server.CreateObject("Msxml2.DOMDocument")
            xmlDoc.async = False
            xmlDoc.validateOnParse = False
            xmlDoc.resolveExternals = False
            fParsed = xmlDoc.loadXML(http.responseText)

            If (Not fParsed) Then
                Exit Do
            End If

            Set xmlErr = Nothing
            Set xmlErr = xmlDoc.selectSingleNode("ProductInfo/ErrorMsg")
            If (Not xmlErr Is Nothing) Then
                Exit Do
            End If

        Set xslDoc = Nothing
            Set xslDoc = Server.CreateObject("Msxml2.DOMDocument")
            xslDoc.async = False
            xslDoc.validateOnParse = False
            xslDoc.resolveExternals = False
        xslDoc.load(Server.MapPath(XSL_FILE))

            szOutput = xmlDoc.transformNode(xslDoc)
            Response.Write szOutput

            ipage = ipage + 1
            If (ipage > nMaxPages) Then
                Exit Do
            End If
        Loop
    End Sub

    ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
    ' Helpers

    Function XMLify(sz)
        XMLify = Replace(sz, "&", "&amp;")
        XMLify = Replace(XMLify, "<", "<")
        XMLify = Replace(XMLify, ">", ">")
        XMLify = Replace(XMLify, """""", """")
        XMLify = Replace(XMLify, "'", "&apos;")
    End Function
%>

This file makes an Amazon Web Services XML/HTTP request based on querystring variables passed in the URL, and transforms the XML locally with an XSL stylesheet. Depending on how much detail you want in the RSS feed, there are two different stylesheets. The first, for light data, is called amazon_lite.xsl.

<?xml version='1.0'?>
<xsl:stylesheet version="1.0" 
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" />
<xsl:template match="ProductInfo/Details">
    <item><link>
    <xsl:value-of select="@url" />
    </link><title>
    <xsl:value-of select="ProductName" />
    </title><description>
        <xsl:text>Author: </xsl:text>
        <xsl:value-of select="Authors/Author[1]" />
        <xsl:text>; </xsl:text>
        <xsl:value-of select="OurPrice" />
        <xsl:if test="Availability">
            <xsl:text> (</xsl:text>
            <xsl:value-of select="Availability" />
            <xsl:if test="Availability = 'Pre Order'">
                <xsl:text>: release date </xsl:text>
                <xsl:value-of select="ReleaseDate" />
            </xsl:if>
            <xsl:text>)</xsl:text>
        </xsl:if>
    </description></item>
</xsl:template>

<xsl:template match="/">
    <xsl:apply-templates select="ProductInfo/Details" />
</xsl:template>

</xsl:stylesheet>

Another stylesheet, appropriately titled amazon_heavy.xsl, provides more detailed information in the feed.

<?xml version='1.0'?>
<xsl:stylesheet version="1.0" 
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" />
<xsl:template match="ProductInfo/Details">
    <item><link>
    <xsl:value-of select="@url" />
    </link><title>
    <xsl:value-of select="ProductName" />
    </title><description>
        <br />
        <xsl:element name="a">
            <xsl:attribute name="href">
                <xsl:value-of select="@url" />
            </xsl:attribute>
            <xsl:element name="img">
                <xsl:attribute name="src">
                    <xsl:value-of select="ImageUrlMedium" />
                </xsl:attribute>
                <xsl:attribute name="border">0</xsl:attribute>
                <xsl:attribute name="hspace">4</xsl:attribute>
                <xsl:attribute name="vspace">4</xsl:attribute>
                <xsl:attribute name="align">left</xsl:attribute>
            </xsl:element>
        </xsl:element>

        <font size="+1">
        <xsl:element name="a">
            <xsl:attribute name="href">
                <xsl:value-of select="@url" />
            </xsl:attribute>
            <xsl:value-of select="ProductName" />
        </xsl:element>
        </font>
        <br />
        <xsl:text>Author: </xsl:text>
        <xsl:value-of select="Authors/Author[1]" />
        <xsl:text>; </xsl:text>
        <xsl:value-of select="OurPrice" />
        <xsl:if test="Availability">
            <xsl:text> (</xsl:text>
            <xsl:value-of select="Availability" />
            <xsl:if test="Availability = 'Pre Order'">
                <xsl:text>, release date </xsl:text>
                <xsl:value-of select="ReleaseDate" />
            </xsl:if>
            <xsl:text>)</xsl:text>
        </xsl:if>
        <br clear="all" />

        <xsl:for-each select="Reviews/CustomerReview">
            <xsl:choose>
                <xsl:when test="Rating = 1">
                    <img src="http://g-images.amazon.com/images/G/01/[RETURN]
detail/stars-1-0.gif" border="0" hspace="2" vspace="2" />
                </xsl:when>
                <xsl:when test="Rating = 2">
                    <img src="http://g-images.amazon.com/images/G/01/[RETURN]
detail/stars-2-0.gif" border="0" hspace="2" vspace="2" />
                </xsl:when>
                <xsl:when test="Rating = 3">
                    <img src="http://g-images.amazon.com/images/G/01/[RETURN]
detail/stars-3-0.gif" border="0" hspace="2" vspace="2" />
                </xsl:when>
                <xsl:when test="Rating = 4">
                    <img src="http://g-images.amazon.com/images/G/01/[RETURN]
detail/stars-4-0.gif" border="0" hspace="2" vspace="2" />
                </xsl:when>
                <xsl:when test="Rating = 5">
                    <img src="http://g-images.amazon.com/images/G/01/[RETURN]
detail/stars-5-0.gif" border="0" hspace="2" vspace="2" />
                </xsl:when>
            </xsl:choose>
            <b><xsl:value-of select="Summary" /></b>
            <br />
            <xsl:value-of select="Comment" />
            <br /><br />
        </xsl:for-each>
    </description></item>
</xsl:template>

<xsl:template match="/">
    <xsl:apply-templates select="ProductInfo/Details" />
</xsl:template>

</xsl:stylesheet>

85.3 Running the Hack

The main file amazon_rss.asp accepts a few querystring variables. One of these is required each time you run the script.

keywords

The subject of the books in the RSS feed.

browse

Use this if you know the browse node code you'd like to syndicate.

author

Set to the author's name to syndicate a list of their books.

Make all three files available on a web server, and then browse to amazon_rss.asp with a variable included. For example:

http://example.com/amazon_rss.asp?keywords=hacks

Now anyone can add this URL to their RSS news reader!

?Sean Nolan