From the web site:

Compass is a first class open source Java Search Engine Framework, enabling the power of Search Engine semantics to your application stack decoratively. Built on top of the amazing Lucene Search Engine, Compass integrates seamlessly to popular development frameworks like Hibernate and Spring. It provides search capability to your application data model and synchronizes changes with the datasource. With Compass: write less code, find data quicker.

As of version 0.8, Compass also provides a Lucene Jdbc Directory implementation, allowing storing Lucene index within a database for both pure Lucene applications and Compass enabled applications. Note, when using Compass, using a database as the index storage requires only updating configuration settings.

 

From the website:

The goal of MARC4J is to provide an easy to use Application Programming Interface (API) for working with MARC and MARCXML in Java. MARC stands for MAchine Readable Cataloging and is a widely used exchange format for bibliographic data. MARCXML provides a loss-less conversion between MARC (MARC21 but also other formats like UNIMARC) and XML.