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.
Ujorm is an easy-to-use ORM framework based on key-value objects. The framework was designed for rapid Java development with great performance and a small footprint. The key features are type safe queries, relation mapping by Java code, no entity states, and a memory overloading protection cache.
EJDB is an embedded JSON database engine. It aims to be a fast MongoDB-like NoSQL library that can be embedded into C/C++/Nodejs/Python3/Lua applications. It features collection-level write locking, collection level transactions, string token matching queries, and a Node.js binding.
Wikitty is a key/value storage and search system. A Java object or a relational table is frozen when writing code or creating a database. To make them evolve, you have to go back into the code, write a migration process, etc. It is also hard to maintain coherent code when you want to develop the same application for similar needs with only small differences. Between the common code and the specific code, it can easily become a real burden. Wikitty tries to answer those problems, bringing a technical solution which is easy to put into place and to use.
persistence4j is a small and lightweight Java object persister that uses JDBC to persist data into a relational database. The library frees you from writing the Data transfer objects - just create a POJO and simply save it. Transactional and non-transactional connections are supported and can be configured from the simple properties file.