Hibernate Search uses Lucene and adds some sugar on it.
Some advantages of Hibernate Search over raw Lucene: - changes in your database (made by Hibernate Core) are propagated transparently for you to the Lucene index - indexing is optimized for you. HSearch does for Lucene that Hibernate Core does for JDBC - queries return managed objects instead of the Lucene Document (which is basically a hashMap of Strings - clustering out of the box
Hibernate Search uses Lucene. The reason of our choice is mainly: - OSS - the best and most popular full-text search library out there
While we could theorically use a different search engine, it is not possible today. Unfortunately the Full-text world does not offer a standard (there is no JPA spec for full-text search) and differences between libraries are quite big.
That being said, integrating with Solr (a product build on top of Lucene too) is probably possible with some work (not trivial but possible I think).