About primary key

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JDO Doc
5

Element.generateForeignKey

Annotation Element javax.jdo.annotations.Element String generateForeignKey Generate or assume a foreign key constraint exists on the column or columns associated with this join. Specify "true" or "false". Returns: whether to generate or assume a primary key constraint Default value: "" Since: JDO 2.1
JDO Doc
5

getObjectId(pc)

JDO vendors only for instances of persistence capable classes using application-managed (primary key ... the transaction, by the application modifying one or more of the application key fields
JPA Doc
5

JoinColumn.table

that contains the column. If a table is not specified, the column is assumed to be in the primary table ... key mapping strategy, the name of the table of the source entity or embeddable. If the join is for a unidirectional OneToMany mapping using a foreign key mapping strategy, the name of the table
JPA Doc
5

MapKeyJoinColumn.referencedColumnName

the primary key column of the referenced table Default value: "" Since: JPA 2.0 ... Annotation Element javax.persistence.MapKeyJoinColumn String referencedColumnName (Optional) The name of the column referenced by this foreign key column. The referenced column is in the table
JPA Doc
5

MapsId.value

Annotation Element javax.persistence.MapsId String value (Optional) The name of the attribute within the composite key to which the relationship attribute corresponds. If not supplied, the relationship maps the entity’s primary key. Default value: "" Since: JPA 2.0
JPA Doc
5

javax.persistence.OneToOne

that assumes both the source and target share the same primary key values. // On Employee class ... embedded field or property. Example 1: One-to-one association that maps a foreign key column
Forum
5

em.flush(); em.clear(); loosing data and not persisting managed objects

that should fix this bug. This fix works except when the primary key is a string. Attached is my test code ... the length of primary keys, but large strings as demonstrated by this test should be avoided, if possible, because a primary key whose length is larger than about 45 bytes is much less efficient. I"m
Forum
5

Should derived fields of an EmbeddedId be manually maintained by app code?

If I have an Entity which has a primary key which is derived and I am implementing it using ... with an EmbeddedId where the containing Entity has a simple Primary Key, and a case which shows an Entity whose container has a Primary Key which is partly a Primary Key. 2) I have kept the Entity classes in
Result
5

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FAQ
5

Which API should I use - JPA or JDO?

You can use ObjectDB with either the Java Persistence API (JPA) or the Java Data Objects (JDO) API. Both share similar architecture, design and abilities. When to prefer JPA JPA is more commonly used. Therefore, it might be the first choice for most new applications. You can use JPA as the primary