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.
Querydsl is a framework that enables the construction of statically typed SQL-like queries. Instead of writing queries as inline strings or externalizing them into XML files, they can be constructed via a fluentDSL/API like Querydsl. It supports JPA, JDO, Java Collections, SQL via JDBC, Lucene, and Hibernate Search.