Butterfly Persistence is a simple, no nonsense Java persistence API. It aims to provide a simple relational persistence API. Its features include automatic/manual connection management, easier JDBC operations via JDBC templates (Spring style), simple object relational mapping, and map reading for dynamic queries. It provides a simple and pragmatic approach to persistence and will either help you, or get out of the way and let you do the job manually.
The Generic Repository (grepo) is a framework for Java which allows you to access (database) repositories in a generic and consistent manner. Using grepo, it is generally no longer required to provide all the boilerplate code which is necessary in order to access (database) repositories from Java. All you have to do is write appropriate database code (queries, procedures, functions, etc.), an appropriately annotated Java interface, and very little Spring configuration.
Midao JDBC simplifies development with Java JDBC. It is flexible, customizable, and simple/intuitive to use, and provides a lot of functionality: transactions, working with metadata, type handling, profiling, input/output processing/converting, pooled datasource libraries support, cached/lazy query execution, named parameters, multiple vendor support out of the box, custom exception handling, and overrides. With a single jar, it supports both JDBC 3.0 (Java 5) and JDBC 4.0 (Java 6). Midao JDBC is well tested. Not only does it have around 700 unit and functional tests, but it's also tested with the latest drivers of Derby, MySQL (MariaDB), PostgreSQL, Microsoft SQL, and Oracle. Midao is a data-centric project. Its goal is to shield Java developer from nuances of vendor implementation and standard boilerplate code. Midao JDBC is the first library released under it.
persistence4j is a small and lightweight Java object persister that uses JDBC to persist data into a relational database. The library frees you from writing the Data transfer objects - just create a POJO and simply save it. Transactional and non-transactional connections are supported and can be configured from the simple properties file.