Object Relational Mapping / Data Persistency

• Hibernate

Relational Persistence for Java and .NET.Historically, Hibernate facilitated the storage and retrieval of Java domain objects via Object/Relational Mapping. Today, Hibernate is a collection of related projects enabling developers to utilize POJO-style domain models in their applications in ways extending well beyond Object/Relational Mapping.
http://www.hibernate.org

• Oracle TopLink

Oracle TopLink delivers a proven standards based enterprise Java solution for all of your relational and XML persistence needs based on high performance and scalability, developer productivity, and flexibility in architecture and design.
http://www.oracle.com/technetwork/middleware/toplink/overview/index.html

• Castor

Castor is an Open Source data binding framework for Java[tm]. It's the shortest path between Java objects, XML documents and relational tables. Castor provides Java-to-XML binding, Java-to-SQL persistence, and more.
http://www.castor.org/

• FireStorm/DAO

FireStorm/DAO makes Java software developers more productive by automatically generating Java source code for data persistence.
http://www.codefutures.com/object-persistence/

• ObJect Relational Bridge

Apache ObJectRelationalBridge (OJB) is an Object/Relational mapping tool that allows transparent persistence for Java Objects against relational databases
http://db.apache.org/ojb/

• iBATIS / mybatis

Apache iBATIS is retired at the apache software foundation (2010/06/16)
The MyBatis data mapper framework makes it easier to use a relational database with object-oriented applications. MyBatis couples objects with stored procedures or SQL statements using a XML descriptor or annotations. Simplicity is the biggest advantage of the MyBatis data mapper over object relational mapping tools.
http://code.google.com/p/mybatis/
http://www.mybatis.org/
http://ibatis.apache.org/

• EclipseLink

The EclipseLink project delivers a comprehensive open-source Java persistence solution addressing relational, XML, and database web services.
It will run in any Java environment and read and write objects to virtually any type of data source, including relational databases, XML, or EIS systems
EclipseLink will focus on providing leading edge support, including advanced feature extensions, for the dominant persistence standards for each target data source; Java Persistence API (JPA) for relational databases, Java API for XML Binding (JAXB) for XML, Java Connector Architecture (JCA) for EIS and other types of legacy systems, and Service Data Objects (SDO).
 
http://www.eclipse.org/eclipselink/