EclipseLink 2.4.0 Juno - RELEASED
As part of the Juno Eclipse release train the EclipseLink project has released EclipseLink 2.4.0. The release landing page describes some of the new and noteworthy features as well as providing links to documentation and examples so you can get started. What I would like to do is provide some colour commentary on the features new in this release.JSON Binding
EclipseLink’s
MOXy component has offered a JAXB compliant implementation for
many years now. It not
only supports the standard JAXB features but also goes well
beyond the standard to offer powerful advanced features,
including XPath mappings, and support for defining mappings in
XML instead of just annotations.
In
EclipseLink 2.4.0, MOXy has expanded its scope to support
mapping Java objects to JSON. This support covers all of the
MOXy mappings available in annotations, XML, and now JSON.
MOXy’s JSON support is
enabled simply by setting the desired media-type on a
marshaller or unmarshaller. This
support is unique as it marshalls/unmarshalls objects directly
to and from JSON without any intermediate conversions. And EclipseLink MOXy’s
integration with EclipseLink JPA, originally written for XML
mapping, makes serializing JPA entities to and from JSON easy.
HTML5/Mobile
During the development of 2.4 the team introduced JSON binding and we started building sample applications illustrating how this functionality could be leveraged with JAX-RS to simplify development. This lead us to discussions with the Jersey team as to how EclipseLink could better integrated. I parallel we continue to look at different client technologies to see what we can do in the persistence layer to simplify development. The convergence of these efforts is EclipseLink's JPA-RS feature which provides RESTful access to persistence units with either XML or JSON data formats.What I find most interesting about JPA-RS is what it offers to developers looking to access data for Thin Server Architecture (TSA) clients. In many cases client developers just need data in a consumable (and of course efficient and secure) format and having to build a full Java EE application to expose this data can be a barrier to entry. What we have done with JPA-RS is simplified how new applications can be developed with a JAX-RS+JPA back-end with minimal server side development.
Cloud Enabled Persistence
Starting in EclipseLink 2.3 the EclipseLink team started exposing features to simplify development of applications that will be deployed in a cloud infrastructure or need to work in PaaS or SaaS scenarios. The solutions introduced included:- @Multitenant(SINGLE_TABLE) allowing tables to store data from multiple tenants leveraging row level filtering.
- Extensible entities using virtual attributes so that the entity types can be customized post deployment to manage additional state.
- MetadataSource allows overriding mapping metadata (JPA and MOXy) to be retrieved dynamically during deployment or on refresh request. This allows persistence unit customization post development so that applications can be customizable at runtime as well as supporting deployment architectures where tenant specific extensions are enabled.
- @Multitenant(TABLE_PER_TENANT) allows different tables in the same schema to be used per tenant or dedicated schemas per tenant.
- MetadataSource has been extended to allow persistence unit properties, including data source information, to be dynamically provided at startup and refresh. This allows PaaS deployed application instances to retrieve isolated data source information per tenant.
NoSQL
EclipseLink,
even before it was open
sourced at Eclipse, offered developers support for mapping their
persistent
entities to non-relational data sources. This support was done
using the
little known EIS features where JCA resource adapters were used
and mappings
were made to XML or record structures. This
core support in the foundation component has been reborn in the
EclipseLink
NoSQL component. This first release of EclipseLink NoSQL that
ships in
conjunction with our primary 2.4.0 release provides mapping and
querying
capabilities with MongoDB and Oracle NoSQL.
Although
Object-Relational
persistence for NoSQL may not apply in all scenarios it does
appeal to
developers who wish to use Objects and find the existing Java
Persistence
interfaces more natural to integrate with versus a unique
data-centric API
provided by the NoSQL vendors.
