CRest (Client REST) is a lightweight library that simplifies the integration of third party RESTful services into Java applications. CRest is mainly annotation-driven, allowing the developer to focus on the essential aspects of the integration of a REST service, such as the definition of the Java interface that maps the remote REST methods and the data model the interface will deal with. The rest is achieved by annotating a plain Java interface with the relevant information such as the service end-point, the desired timeouts, URL formats, etc. CRest will handle everything else, including HTTP request generation, auto marshalling of the response, and more.
Corn Gate is designed to simplify service definitions and implementations in Java. It comes with several handy out-of-the-box functionalities, including security, registry, Spring and EJB integration, filters, shared data stages, client contexts, etc. JSON-RPC/HTTP and REST/HTTP protocols are supported. Remote service calls can be done through various client technologies. Since Gate supports standard HTTP communication mechanisms, almost any client technology can access services remotely.
DataNucleus AccessPlatform is a standards-compliant Java persistence product. It is fully compliant with the JDO1, JDO2, JDO2.1, JDO2.2, JDO3, JPA1, JPA2 and JPA2.1 Java standards, and provides a REST API. It complies with the OGC Simple Feature Spec for persistence of geospatial Java types. It allows access to all popular RDBMS available today, together with the MongoDB, LDAP, NeoDatis, JSON, Excel/ODF spreadsheets, XML, BigTable, HBase, and Neo4j databases.
Django REST framework is a lightweight REST framework for Django that aims to make it easy to build well-connected, self-describing RESTful Web APIs. It creates self-documenting Web APIs that include a Django admin style frontend. It has a modular, flexible architecture using Django's class based views. API creation can be as simple as adding a couple of lines to urls.py.