Solr dataimport is reporting file not found when it looks for foo.xml. Where is it looking for /data? is this an url off the apache2/htdocs on the server, or is it an URL within example/solr/...?
<entity name="page"
processor="XPathEntityProcessor"
stream="true"
forEach="/mediawiki/page/"
url="/data/foo.xml"
transformer="RegexTransformer,DateFormatTransformer"
>
