Fast Object Database for Java - with JPA/JDO support

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Auto Generated Values

generated for that field. This is primarily intended for primary key fields but ObjectDB also supports ... for entity objects with no primary key fields defined (as explained in the previous section). The same number generator is also used to generate numeric values for primary key fields annotated by

Retrieving JPA Entity Objects

of entity classes and to keep them simple as possible. Retrieval by Class and Primary Key Every entity object can be uniquely identified and retrieved by the combination of its class and its primary key ... whose primary key is 1: Employee employee = em.find(Employee.class, 1); Casting of the retrieved

Defining a JPA Entity Class

, including which persistent types can be used for persistent fields, how to define and use a primary key ... you might have noticed that the Point entity class has no primary key (@Id) field. As an object database, ObjectDB supports implicit object IDs, so an explicitly defined primary key is not required. On the other hand

JPA Entity Fields

(Mapped By) fields Primary key (ID) fields Version field The first three groups (transient, persistent ... two groups (primary key and version fields) can only be used in entity classes. Primary key fields are discussed in the Primary Key section. Transient Fields Transient entity fields are fields

Index Definition

field (similar to how primary keys behave). @Index represents either an ordinary index ... can only be defined on ordinary persistent fields (not on primary key / version fields). Composite Index A composite ... the BTree's primary sort key and which field is used as a secondary sort key. If x is specified first


javax.jdo.annotations Annotation Key Target: Fields (including property get methods) Annotation for the key of a map relation. Corresponds to the xml element "key". Since: JDO 2.1 String column Name of the column to store the key in. Name of the column to store the key in. Returns: name

Inserted entities with strings as keys and indices needs more and more ram memory in comparing to primitive integers as keys and indices

Hello, I have a problem with inserting of many entities. We use strings as primary key and indices ... ? See both examples. btc_es BTC EmbeddedSystems Correction. The case with strings as primary key and indices ... programs demonstrate well that automatic long primary keys are indeed much more efficient than String

Database Explorer

and primary key separated by # (e.g. Point#1). A collection can be specified as a comma separated list ... to set a reference to an existing entity object, which has to be specified by type and primary key ... to an existing entity object, which has to be specified by type and primary key separated by # (e.g

Is ObjectDB better than competing object databases?

databases do not support user defined primary keys, even though this is very useful in almost every application. ObjectDB supports user defined primary keys including composite primary keys. The support


Annotation Element javax.jdo.annotations.Key ForeignKeyAction deleteAction Delete action to apply to the foreign key for the key. Returns: delete action to apply to the foreign key for the key Default value: javax.jdo.annotations.ForeignKeyAction.UNSPECIFIED Since: JDO 2.1

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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