Creating Canonical URLs

To code your JSPs to render canonical URLs, you use the URL recoding feature described in the URL Recoding section. The canonical URL generated for a page is similar to the static URL rendered for web spiders by an indirect URL template. The canonical URL should always be static, regardless of whether the page is accessed by a spider or a human user. That way, if a spider happens to access a page using a dynamic URL (e.g., by following a link from another page), it will still see (and record) the static URL it finds in the link tag. As with the URL recoding feature, when a user accesses a page via a static URL, the SEO jump servlet translates it back to its dynamic equivalent for processing.

To render canonical URLs, you use the atg.repository.seo.CanonicalItemLink servlet bean. This class is similar to the ItemLink servlet bean, except that it does not use template mappers, because the URL template used does not depend on the browser type of the request. So rather than configuring the ItemLink servlet bean’s itemDescriptorNameToMapperMap property to map item descriptors to UrlTemplateMapper components, you configure the CanonicalItemLink servlet bean’s itemDescriptorNameToUrlTemplateMap property to map item descriptors directly to UrlTemplate components. For example:

itemDescriptorNameToUrlTemplateMap=\
        product=/atg/repository/seo/ProductIndirectTemplate,\
        category=/atg/repository/seo/CategoryIndirectTemplate

The following example illustrates using the CanonicalItemLink servlet bean on a product detail page to render a link tag specifying the page’s canonical URL:

<dsp:droplet name="/atg/repository/seo/CanonicalItemLink">
  <dsp:param name="id" param="productId"/>
  <dsp:param name="itemDescriptorName" value="product"/>
  <dsp:param name="repositoryName"
     value="/atg/commerce/catalog/ProductCatalog"/>
  <dsp:oparam name="output">
    <dsp:getvalueof var="pageUrl" param="url" vartype="java.lang.String"/>
    <link rel="canonical" href="${pageUrl}"/>
 </dsp:oparam>
</dsp:droplet>

For additional information about the CanonicalItemLink servlet bean, see the ATG Page Developer's Guide.