Mapping extensions allow you to access Kodo-specific functionality from your mappings. Note that all extensions below are specific to mappings. If you store your mappings separately from your persistence metadata, these extensions must be specified along with the mapping information, not the persistence metadata information.
It is only valid to place these extensions on JDO persistence metadata
if you store your mappings in your .jdo
files, or
if you want these extensions to act as mapping hints
(see Section 7.1.3, “
JDO Forward Mapping Hints
”).
All extension keys use a vendor-name
of
kodo
.
Kodo recognizes the following class extensions.
This extension specifies how to eagerly fetch subclass state.
It overrides the global
kodo.jdbc.SubclassFetchMode
property.
Set the JPA
kodo.persistence.jdbc.SubclassFetchMode
annotation to a value from the
kodo.persistence.jdbc.EagerFetchType
enum: JOIN
,
PARALLEL
, or NONE
.
Set the JDO jdbc-subclass-fetch-mode
XML
extension key to join
,
parallel
, or none
.
See Section 5.7, “Eager Fetching” for a
discussion of eager fetching.
The
kodo.persistence.jdbc.Strategy
class annotation allows you to specify a custom mapping
strategy for your class. See
Section 7.10, “Custom Mappings” for information on
custom mappings.
Note that this extension applies only to JPA
mapping; when using JDO mappings you specify custom class
strategies using the standard XML inheritance
element's strategy
attribute.
The
kodo.persistence.jdbc.DiscriminatorStrategy
class annotation allows you to specify a
custom discriminator strategy. See
Section 7.10, “Custom Mappings” for information on
custom mappings.
Note that this extension applies only to JPA
mapping; when using JDO mappings you specify custom
discriminator strategies using the standard XML
discriminator
element's
strategy
attribute.
The
kodo.persistence.jdbc.VersionStrategy
class annotation allows you to specify a custom
version strategy. See
Section 7.10, “Custom Mappings” for information on
custom mappings.
Note that this extension applies only to JPA
mapping; when using JDO mappings you specify custom
version strategies using the standard XML version
element's strategy
attribute.
Kodo recognizes the following field extensions.
This extension specifies how to eagerly fetch related objects.
It overrides the global
kodo.jdbc.EagerFetchMode
property.
Set the JPA
kodo.persistence.jdbc.EagerFetchMode
annotation to a value from the
kodo.persistence.jdbc.EagerFetchType
enum: JOIN
,
PARALLEL
, or NONE
.
Set the JDO jdbc-eager-fetch-mode
XML
extension key to join
,
parallel
, or none
.
See Section 5.7, “Eager Fetching” for a
discussion of eager fetching.
All fields in Java are polymorphic. If you declare a
field of type T
, you can assign any subclass
of T
to the field as well. This is very
convenient, but can make relation traversal very inefficient
under some inheritance strategies. It can even make querying
across the field impossible. Often, you know that certain
fields do not need to be entirely polymorphic. By telling
Kodo about such fields, you can improve the efficiency of your
relations.
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Kodo also includes the |
Kodo JPA defines the following extensions for nonpolymorphic values:
kodo.persistence.jdbc.Nonpolymorphic
kodo.persistence.jdbc.ElementNonpolymorphic
kodo.persistence.jdbc.KeyNonpolymorphic
The value of these extensions is a constant from the
kodo.persistence.jdbc.NonpolymorphicType
enumeration. The default value,
EXACT
, indicates that the relation will always be of
the exact declared type. A value of
JOINABLE
, on the other hand, means that the relation
might be to any joinable subclass of the declared type. This
value only excludes table-per-class subclasses.
Kodo JDO defines the following nonpolymorphic mapping extension keys:
jdbc-nonpolymorphic
jdbc-element-nonpolymorphic
jdbc-key-nonpolymorphic
jdbc-value-nonpolymorphic
These keys apply to field values, collection or array elements,
map keys, and map values, respectively. Set the extension
value to exact
to indicate that the relation
is always to the exact declared type. Set it to
joinable
if the relation can be to any joinable
subclass of the declared type. A value of joinable
only excludes table-per-class subclasses.
This family of boolean extensions determines whether Kodo will
use the expected class of related objects as criteria in the SQL
it issues to load a relation field. Typically, this is
not needed. The foreign key values uniquely identify the
record for the related object. Under some rare mappings,
however, you may need to consider both foreign key values and
the expected class of the related object - for example, if
you have an inverse relation that shares the
foreign key with another inverse relation to an object
of a different subclass. In these cases, set the proper class
critera extension to true
to force Kodo to
append class criteria to its select SQL.
Kodo JPA defines the following class criteria annotations for field relations, array, collection, and map element relations, and map key relations, respectively:
kodo.persistence.jdbc.ClassCriteria
kodo.persistence.jdbc.ElementClassCriteria
kodo.persistence.jdbc.KeyClassCriteria
Kodo JDO defines the following class criteria mapping extension keys for field relations, collection and array element relations, map key relations, and map value relations, respectively:
jdbc-class-criteria
jdbc-element-class-criteria
jdbc-key-class-criteria
jdbc-value-class-criteria
Kodo's family of strategy extensions allow you to specify a custom mapping strategy or value handler for a field. See Section 7.10, “Custom Mappings” for information on custom mappings.
Kodo includes the following JPA strategy annotations:
kodo.persistence.jdbc.Strategy
: Field strategy or value handler
plugin string.
kodo.persistence.jdbc.ElementStrategy
: Array, collection, or map element
value handler plugin string.
kodo.persistence.jdbc.KeyStrategy
: Map key value handler plugin
string.
Kodo recognizes the following JDO strategy extension keys:
jdbc-strategy
: Field strategy or
value handler plugin string.
jdbc-element-strategy
: Collection or
array element value handler plugin string.
jdbc-key-strategy
: Map key value
handler plugin string.
jdbc-value-strategy
: Map value
handler plugin string.
Kodo recognizes the following extensions within JDO
column
elements:
This extension is only valid on version columns. When you use custom lock groups, it allows you to declare which version column is for which lock group. See Section 5.8, “Lock Groups”.
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