Nutch Content Filtering

[mausmust]

While Apache Nutch 1.3 crawling pages, i want to analyze the content of 
the page and if the content contains some keywords then adding page for 
next steps, say indexing. If the content do not contains at least one 
key, then just getting links from that page and ignoring it. How can i 
do that? Is there any filtering plugin available for this purpose? Thnx.