With MetaModel, you use a type-safe SQL-like API for querying any datastore. It is a data access framework providing a common interface for exploration and querying of different types of datastores. It isn't a data mapping framework. Instead, it emphasizes abstraction of metadata and the ability to add data sources at runtime, making MetaModel great for generic data processing applications, but less so for applications modeled around a particular domain.
Spring is a lightweight Java/J2EE application framework based on code published in "Expert One-on-One J2EE Design and Development" by Rod Johnson. It includes powerful JavaBeans-based configuration management applying Inversion-of-Control principles, a generic abstraction layer for transaction management allowing for pluggable transaction managers, a JDBC abstraction layer, integration with Hibernate, JDO, Apache OJB, and iBATIS SQL Maps, AOP functionality, and a flexible MVC Web application framework with multiple view technologies. There is also a .NET port available.
Mr. Persister aims at providing a simple yet complete relational persistence API. Current features include easier JDBC operations via JDBC templates (Spring style), automatic connection/transaction handling, object relational mapping, dynamic report support, connection pooling, and more. Planned features include replication, JDBC driver debugging, more advanced ORM, and more.
OpenJPA is a 100% compliant feature-rich implementation of the persistence part of Enterprise Java Beans 3.0, also known as the Java Persistence API (JPA). It can be used as a stand-alone POJO persistence layer, or it can be integrated into any EJB3.0 compliant container and many lightweight frameworks.
LibMySequoia provides an alternative library for MySQL C client library (libmysqlclient.so) to benefit from the Sequoia high availability and performance scalability clustering solution. Native MySQL client programs can use the Sequoia clustering solution without changing any line of code in the application. The benefit of this solution is that native C applications, PHP, Perl, and Python programs using the MySQL C API interface now can transparently connect to a Sequoia cluster.
XMLImportDB provides an easy-to-use interface that allows developers to create a baseline database environment that can be embedded in their source code for use in jUnit test cases. The database environment can be described in a separate file in the same package as the tests, in a hard coded string in the test case classes, or in any other location for which a java.io.Reader can be created at runtime.