With MetaModel, you use a type-safe SQL-like API for querying any datastore. It is a data access framework providing a common interface for exploration and querying of different types of datastores. It isn't a data mapping framework. Instead, it emphasizes abstraction of metadata and the ability to add data sources at runtime, making MetaModel great for generic data processing applications, but less so for applications modeled around a particular domain.
Berkeley DB Java Edition is a high performance transactional storage engine written entirely in Java. Like the highly successful Berkeley DB product, it executes in the address space of the application without the overhead of client/server communication. It stores data in the application's native format, so no runtime data translation is required. It supports full ACID transactions and recovery, and provides an easy-to-use interface, allowing programmers to store and retrieve information quickly, simply, and reliably.
Berkeley DB XML is a native XML database engine for use within your product. Made available as a C++ library with language bindings for Java, Perl, Python, PHP, and Tcl, it integrates directly into your application (it is not a standalone database server). It provides XQuery access into a database of document containers. XML documents are stored and indexed in their native format using Berkeley DB as the transactional database engine.
CloverETL is Java-based tool/framework for data integration and creation of data transformations. It is component based and follows the concept of transformation graphs which consist of individual nodes/components performing simple (or complex) operations on data. Any transformation can be defined as a set of interconnected nodes through which data flows. CloverETL can be used as a standalone application or be embedded into a larger project.
HeliDB is a database for storing key-value pairs from a Java program. The client program creates one database object per database file. The database objects can be configured to support different capabilities. In its simplest configuration, a database is a file-backed map. More advanced configurations can give it transaction support or fast record searches by indexing records in a B+ tree.
JPOX provides transparent persistence of Java objects. It fully complies with the JDO1.0/JDO2.0/JDO2.1/JPA1 specifications. It supports persistence to all of the major RDBMSs on the market today, as well as DB4O. It allows querying using JDOQL, SQL, or JPQL. It comes with its own byte-code enhancer. Its 1.1 release is Sun's "Reference Implementation" (RI) for JDO2.0, and its 1.2 release is the RI for JDO2.1. It is highly extensible, using OSGi technology and providing a wide range of value-adding plugins.
MUSCLE (Multi User Server Client Linking Environment) is an N-way messaging server and networking API. It includes client-side networking APIs for various languages, including C, C++, C#, Delphi, Java, and Python. MUSCLE lets programs communicate over a network via streams of serialized Message objects. The included server program ("muscled") lets its clients message each other and store information in its server-side hierarchical database. The database supports flexible queries via hierarchical wildcarding, and "live" updates via a subscription mechanism.
MaVerick is a MultiValue database management system. MultiValue databases are said to be one of the computer industry's best kept secrets. First appearing over 30 years ago as PICK, they have continued to evolve through various commercial vendors, and are still in active development today. They are very resource friendly, are incredibly fast, feature a very user friendly data retrieval and reporting language (variously called ACCESS or English), and a rapid application development language based originally on Dartmouth Basic. The MaVerick project is an attempt to create an open source variant, written in Java.