EclipseLink

EclipseLink is a free and open-source tool that facilitates an extensive framework for Java developers to use different kinds of data services, such as databases, Enterprise Information Systems (EIS) and Object XML mapping (OXM), along with XML, relational and database web services.

It is compatible with many persistence standards, such as Java Persistence API (JPA), Java Connector Architecture (JCA), Java Architecture for XML Binding (JAXB), and Service Data Objects (SDO).

JPA is an interface for relational data management in Java tools, including the API, Java Persistence Query Languauge (JPQL) and object - relational metadata. JCA links application servers and enterprise information systems to enterprise application integration. JAXB is a framework for mapping Java classes to XML representations, and it is implemented into EclipseLink as MOXy. Lastly, SDO permits heterogeneous data to be accessed the same way.

When it comes to SQL, users can study basic configuration examples, find out how EclipseLink JPA can be used in a JSF application or JPA tool, and view other JPA examples. There are also no-SQL examples for accessing MongoDB through JPA and for polyglot persistence (relational and no SQL). The project is released under a combination of two licenses: Eclipse Public LIcense 1.0 and Eclipse Distribution License.