Flint library is using Lucene.
With Flint, you can easily read and write data into a Lucene index using a simple XML format (iXML).
The iXML format is a simple XML representation of a Lucene record, for example:
<document>
<field name="id" store="yes" index="no">123</field>
<field name="title" store="yes" index="un-tokenized">My Record</field>
<field name="summary" store="compress" index="tokenized">This is important data I want to be able to search</field>
<document>Flint can load iXML into a Lucene index, but it does not convert original format (XML, PDF, DOCX, HTML, text, etc…) into a Lucene index.
Flint also simplifies the way queries can be aggregated.