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The Java Persistence API (JPA) provides various ways to retrieve objects from the database. The retrieval of objects does not require an active transaction because it does not change the content of the database. The persistence context serves as a cache of retrieved entity objects . If a requested

Entity objects are in-memory instances of entity classes (persistable user defined classes), which can represent physical objects in the database. Managing an ObjectDB Object Database using JPA requires using entity objects for many operations, including storing, retrieving, updating and deleting

Detached entity objects are objects in a special state in which they are not managed by any EntityManager but still represent objects in the database. Compared to managed entity objects , detached objects are limited in functionality: Many JPA methods do not accept detached objects (e.g. lock

New entity objects can be stored in the database either explicitly by invoking the persist method ... (). commit (); The Employee instance is constructed as an ordinary Java object and its initial state is New. An explicit call to persist associates the object with an owner EntityManager em and changes

Existing entity objects can be deleted from the database either explicitly by invoking the remove ... an object from the database it has to first be retrieved (no matter which way) and then in an active ... object is physically deleted from the database when the transaction is committed. Embedded objects

, derived attributes, grouping queries and aggregate queries) which are usually missing from Object Oriented Databases are also supported by ObjectDB. The combination of Object Database features ... . Up to 9,223,372,036,854,775,808 entity objects per database file. Unlimited database connections

Modifying existing entity objects that are stored in the database is based on transparent ... Once an entity object is retrieved from the database (no matter which way) it can simply be modified in memory ... (); The entity object is physically updated in the database when the transaction is committed

solution. Using a relational database management system (RDBMS) to store and retrieve Java objects requires slow conversions between graphs of Java objects and flat database table rows. Object Relational ... , and even add their own overhead. ObjectDB supports direct storage of graphs of objects

. However, you should consider the following points when doing your own objective comparison of object databases: ObjectDB is unique in supporting the standard APIs. It is the only object database with built in ... of the Java Data Objects (JDO) API than competing object databases. By using a standard API such as JPA

This chapter describes how to use ObjectDB to manage database objects . 6.1  Making Objects Persistent In JDO applications, every object in memory is either a persistent object , i.e. represents some database content, or a transient object , i.e. not related to any database. Storing Objects