ObjectDB

ObjectDB is an object database designed for Java applications. It stores Java objects directly in a transactional database, eliminating the need for an object-relational mapping layer. Data is persisted as native objects, preserving references between objects and supporting complex object graphs.

The database can be used as an embedded library within a Java application or run in server mode using the ObjectDB Server. It is designed to be lightweight with fast startup and a small footprint, and it provides ACID-compliant transactions. The persistence model is schema-free; objects and their fields are stored without requiring a predefined relational schema. Developers typically mark persistent classes with JPA annotations, and ObjectDB supports the Java Persistence API for mapping and queries, while also offering its own object query language (OQL) for native object queries.

Key features include support for indexing on fields to speed up queries, handling of large binary objects, and automatic schema generation from persistent classes. It provides robust transaction management and concurrency control to support multi-threaded applications.

In terms of tooling and integration, ObjectDB provides a Java API for creating, querying, updating, and deleting persistent objects. It can be used in a variety of environments where the JVM runs and can be accessed by frameworks and technologies that support JPA.

ObjectDB is a commercial product with licensing options, including evaluation licenses. It is aimed at developers seeking a persistence store that stores objects directly without the overhead of relational mapping.