META-INF/package.jdo
WEB-INF/package.jdo
package.jdo
com/package.jdo
com/mycompany/package.jdo
com/mycompany/sample/package.jdo
com/mycompany/sample/myexample.jdo

com.jdo
com/mycompany.jdo
com/mycompany/sample.jdo

com/mycompany/A.java
com/mycompany/B.java
com/mycompany/C.java
com/mycompany/app1/D.java
com/mycompany/app1/E.java
                

MetaData Format

JDO MetaData has the following format. Please refer to the JDO ORM XSD for precise details. What follows provides a reference guide to MetaData elements.

• jdo
• package
• class
• implements
• datastore-identity
• column
• extension
• primary-key
• column
• inheritance
• discriminator
• column
• join
• column
• version
• column
• extension
• join
• column
• foreign-key
• column
• field
• property
• index
• column
• field
• property
• unique
• column
• field
• property
• field
• collection
• extension
• map
• extension
• array
• join
• primary-key
• column
• embedded
• field
• column
• element
• column
• key
• column
• value
• column
• order
• column
• extension
• column
• extension
• foreign-key
• column
• index
• column
• unique
• column
• extension
• property
• collection
• extension
• map
• extension
• array
• join
• primary-key
• column
• embedded
• field
• column
• element
• column
• key
• column
• value
• column
• order
• column
• column
• extension
• foreign-key
• column
• index
• column
• unique
• column
• extension
• fetch-group
• field
• query
• sequence
• extension
• fetch-plan
• extension
• extension

Metadata for package tag

These are attributes within the <package> tag (jdo/package). This is used to denote a package, and all of the <class> elements that follow are in this Java package.

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the java package
catalog	Name of the catalog in which to persist the classes in this package. See also the property name "javax.jdo.mapping.Catalog" in the PMF Guide.
schema	Name of the schema in which to persist the classes in this package. See also the property name "javax.jdo.mapping.Schema" in the PMF Guide.

Metadata for class tag

These are attributes within the <class> tag (jdo/package/class). This is used to define the persistence definition for this class.

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the class to persist
identity-type	The identity type, specifying whether they are uniquely provided by the JDO implementation (datastore identity), accessible fields in the object (application identity), or not at all (nondurable identity). DataNucleus only supports nondurable identity for SQL views, and NucleusSQL queries .	datastore , application, nondurable
objectid-class	The class name of the primary key. When using application identity .
requires-extent	Whether the JDO implementation must provide an Extent for this class.	true , false
detachable	Whether the class is detachable from the persistence graph.	true, false
embedded-only	Whether this class should only be stored embedded in the tables for other classes.	true, false
persistence-modifier	What type of persistability type this class exhibits. Please refer to JDO Class Types.	persistence-capable | persistence-aware | non-persistent
persistence-capable-superclass	Class name of superclass that is persistent capable. This is deprecated in JDO2 and you no longer need to specify it, leaving it to DataNucleus to determine if there is a superclass that is PersistenceCapable .
catalog	Name of the catalog in which to persist the class. See also the property name "javax.jdo.mapping.Catalog" in the PMF Guide.
schema	Name of the schema in which to persist the class. See also the property name "javax.jdo.mapping.Schema" in the PMF Guide.
table	Name of the table/view in which to persist the class. See also the property name "datanucleus.identifier.case" in the Persistence Properties Guide.
cacheable	Whether the class can be cached in a Level 2 cache. From JDO2.2	true | false

Metadata for implements tag

These are attributes within the <implements> tag (jdo/package/class/implements). This is used when the <class> implements interfaces that are used as field types in other classes. This is deprecated in JDO2.1 since it can be determined from reflection on the class

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the interface being implemented (fully qualified, else will look in the same package)

Metadata for datastore-identity tag

These are attributes within the <datastore-identity> tag (jdo/package/class/datastore-identity). This is used when the <class> to which this pertains uses datastore identity. It is used to define the precise definition of datastore identity to be used. This element can contain column sub-elements allowing definition of the column details where required - these are optional.

Attribute	Description	Values
Standard (JDO) Tags
strategy	Strategy for datastore identity generation for this class. native allows DataNucleus to choose the most suitable for the datastore. sequence will use a sequence (specified by the attribute sequence ) - if supported by the datastore. increment will use the id values in the datastore to decide the next id. uuid-string will use a UUID string generator (16-characters). uuid-hex will use a UUID string generator (32-characters). identity will use a datastore inbuilt auto-incrementing types. auid is a DataNucleus extension, that is an almost universal id generator (best possible derivate of a DCE UUID). max is a DataNucleus extension, that uses "select max(column)+1 from table" for the identity. timestamp is a DataNucleus extension, providing the current timestamp. timestamp-value is a DataNucleus extension, providing the current timestamp millisecs. [other values] to utilise user-supplied DataNucleus value generator plugins.	native | sequence | increment | identity | uuid-string | uuid-hex | auid | max | timestamp | timestamp-value | [other values]
sequence	Name of the sequence to use to generate identity values, when using a strategy of sequence . Please see also the class extension tags for controlling the sequence.
column	Name of the column used for the datastore identity for this class.

These are attributes within the <extension> tag (jdo/package/class/datastore-identity/extension). These are for controlling the generation of ids when in datastore identity mode.

Attribute	Description	Values
Extension (JDO) Tags
sequence-table-basis	This defines the basis on which to generate unique identities when using the TablePoidGenerator (used by the "increment" strategy, and sometimes by "native"). You can either define identities unique against the base table name, or against the base class name (in an inheritance tree). Used when the strategy is set to native or increment	class | table
sequence-catalog-name	The catalog used to store sequences for use by poid generators. See Value Generation. Default catalog for the datastore will be used if not specified.
sequence-schema-name	The schema used to store sequences for use by poid generators. See Value Generation. Default schema for the datastore will be used if not specified.
sequence-table-name	The table used to store sequences for use by poid generators. See Value Generation.	SEQUENCE_TABLE
sequence-name-column-name	The column name in the sequence-table used to store the name of the sequence for use by poid generators. See Value Generation.	SEQUENCE_NAME
sequence-nextval-column-name	The column name in the sequence-table used to store the next value in the sequence for use by poid generators. See Value Generation.	NEXT_VAL
key-min-value	The minimum key value for use by poid generators. Keys lower than this will not be generated. See Value Generation.
key-max-value	The maximum key value for use by poid generators. Keys higher than this will not be generated. See Value Generation.
key-start-with	The starting value for use by poid generators. Keys will start from this value when being generated. See Value Generation.
key-increment-by	The increment value for use by poid generators. Keys will be incremented by this value when being generated. See Value Generation.
key-database-cache-size	The database cache size for keys for use by poid generators. The cache of keys will be constrained by this value. See Value Generation.
key-cache-size	The cache size for keys for use by poid generators. The cache of keys will be constrained by this value. See Value Generation.

Metadata for primary-key tag

These are attributes within the <primary-key> tag (jdo/package/class/primary-key or class/field/join/primary-key). It is used to specify the name of the primary key constraint in the datastore during the schema generation process. When used under <join> it specifies that the join table has a primary-key.

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the primary key constraint.
column	Name of the column to use for the primary key

Metadata for inheritance tag

These are attributes within the <inheritance> tag (jdo/package/class/inheritance). It is used when this class is part of an inheritance tree, and to denote how the class is stored in the datastore since there are several ways (strategies) in which it can be stored.

Attribute	Description	Values
Standard (JDO) Tags
strategy	Strategy for inheritance of this class. Please refer to the Inheritance Guide. Note that "complete-table" is a DataNucleus extension to JDO2	new-table, subclass-table, superclass-table, complete-table

Metadata for discriminator tag

These are attributes within the <discriminator> tag (jdo/package/class/inheritance/discriminator). This is used to define a discriminator column that is used when this class is stored in the same table as another class in the same inheritance tree. The discriminator column will contain a value for objects of this class, and different values for objects of other classes in the inheritance tree.

Attribute	Description	Values
Standard (JDO) Tags
strategy	Strategy for the discrimination column	value-map | class-name | none
value	Value for the discrimination column
column	Name for the discrimination column
indexed	Whether the discriminator column should be indexed. This is to be specified when defining index information	true | false | unique

Metadata for version tag

These are attributes within the <version> tag (jdo/package/class/version). This is used to define whether and how this class is handled with respect to optimistic transactions.

Attribute	Description	Values
Standard (JDO) Tags
strategy	Strategy for versioning of this class. The "version-number" mode uses an incremental numbered value, and the "date-time" mode uses a java.sql.Timestamp value. state-image isn't currently supported.	state-image, date-time, version-number
column	Name of the column in the datastore to store this field
indexed	Whether the version column should be indexed. This is to be specified when defining index information	true | false | unique

These are attributes within the <extension> tag (jdo/package/class/version/extension).

Attribute	Description	Values
Extension (JDO) Tags
field-name	This extension allows you to define a field that will be used to contain the version of the object. It is populated by DataNucleus at persist. See JDO Versioning

Metadata for query tag

These are attributes within the <query> tag (jdo/package/class/query). This element is used to define any "named queries" that are to be available for this class. This element contains the query single-string form as its content.

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the query. This name is mandatory and is used in calls to pm.newNamedQuery() . Has to be unique for this class.
language	Query language to use. Some datastores offer other languages	JDOQL | SQL | JPQL | NucleusSQL
unique	Whether the query is to return a unique result (only for SQL queries).	true | false
result-class	Class name of any result class (only for SQL queries).

Metadata for field tag

These are attributes within the <field> tag (jdo/package/class/field). This is used to define the persistence behaviour of the fields of the class to which it pertains. Certain types of fields are, by default, persisted. This element can be used to change the default behaviour and maybe not persist a field, or to persist something that normally isn't persisted. It is used, in addition, to define more details about how the field is persisted in the datastore.

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the field.
persistence-modifier	The persistence-modifier specifies how JDO manage each field in your persistent class. There are three options: persistent, transactional and none. persistent means that your field will managed by JDO and stored in the database on transaction commit. transactional means that your field will managed by JDO but not stored in the database. Transactional fields values will be saved by JDO when you start your transaction and restored when you roll back your transaction. none means that your field will not be managed by JDO.	persistent, transactional, none
primary-key	Whether the field is part of any primary key (if using application identity ).	true, false
null-value	How to treat null values of persistent fields during storage. Valid options are "exception", "default", "none" (where "none" is the default).	exception, default, none
default-fetch-group	Whether this field is part of the default fetch group for the class. Defaults to true for non-key fields of primitive types, java.util.Date, java.lang.*, java.math.*, etc.	true , false
embedded	Whether this field should be stored, if possible, as part of the object instead as its own object in the datastore. This defaults to true for primitive types, java.util.Date, java.lang.*, java.math.* etc and false for PersistenceCapable, reference (Object, Interface) and container types.	true, false
serialized	Whether this field should be stored serialised into a single column of the table of the containing object.	true, false
dependent	Whether the field should be used to check for dependent objects, and to delete them when this object is deleted. In other words cascade delete capable.	true, false
mapped-by	The name of the field at the other end of a relationship. Used by 1-1, 1-N, M-N to mark a relation as bidirectional.
value-strategy	The strategy for populating values to this field. Is typically used for generating primary key values. See the definitions under "datastore-identity".	native | sequence | increment | identity | uuid-string | uuid-hex | auid | max | timestamp | timestamp-value | [other values]
sequence	Name of the sequence to use to generate values, when using a strategy of sequence . Please see also the class extension tags for controlling the sequence.
recursion-depth	The depth that will be recursed when this field is self-referencing. Should be used alongside FetchPlan.setMaxFetchDepth() to control the objects fetched.	-1, 1 , 2, ... (integer)
field-type	Used to specify a more restrictive type than the field definition in the class. This might be required in order to map the field to the datastore. To be portable, specify the name of a single type that is itself able to be mapped to the datastore (e.g. a field of type Object can specify field-type="Integer").
indexed	Whether the column(s) for this field should be indexed. This is to be specified when defining index information	true | false | unique
table	Table name to use for any join table overriding the default name provided by DataNucleus. This is used either for 1-N relationships with a join table or for Secondary Tables. See also the property name "datanucleus.identifier.case" in the Persistence Properties Guide.
column	Column name to use for this field (alternative to specifying column sub-elements if only one column).
delete-action	The foreign-key delete action. This is a shortcut to specifying foreign key information. Please refer to the <foreign-key> element for full details.	cascade | restrict | null | default | none
cacheable	Whether the field/property can be cached in a Level 2 cache. From JDO2.2	true | false

These are attributes within the <extension> tag (jdo/package/class/field/extension).

Attribute	Description	Values
Extension (JDO) Tags
cascade-persist	JDO defines that when an object is persisted then all fields will also be persisted using "persistence-by-reachability". This extension allows you to turn off the persistence of a field relation.	true | false
cascade-update	JDO defines that when an object is updated then all fields containing PersistenceCapable objects will also be updated using "persistence-by-reachability". This extension allows you to turn off the update of a field relation.	true | false
cascade-refresh	When calling PersistenceManager.refresh() only fetch plan fields of the passed object will be refreshed. Setting this to true will refresh the fields of related PC objects in this field	true | false
allows-null	When the field is a collection by default it will not be allowed to have nulls present but you can allow them by setting this DataNucleus extension tag	true | false
insertable	Whether this field should be supplied when inserting into the datastore.	true | false
updateable	Whether this field should be supplied when updating the datastore.	true | false
adapter-column-name	In some situations DataNucleus will add a special datastore column to a join table so that collections can allow the storage of duplicate elements. This extension allows the specification of the column name to be used. This should be specified within the field at the collection end of the relationship. JDO2 doesnt allow a standard place for such a specification and so is an extension tag.	INTEGER_IDX
implementation-classes	Used to define the possible classes implementing this interface/Object field. This is used to limit the possible tables that this is a foreign key to (when this field is specified as an interface/Object in the class). Value should be comma-separated list of fully-qualified class names
key-implementation-classes	Used to define the possible classes implementing this interface/Object key. This is used to limit the possible tables that this is a foreign key to (when this key is specified as an interface/Object). Value should be comma-separated list of fully-qualified class names
value-implementation-classes	Used to define the possible classes implementing this interface/Object value. This is used to limit the possible tables that this is a foreign key to (when this value is specified as an interface/Object). Value should be comma-separated list of fully-qualified class names
strategy-when-notnull	This is to be used in conjunction with the "value-strategy" attribute. Default JDO2 behaviour when you have a "value-strategy" defined for a field is to always create a strategy value for that field regardless of whether you have set the value of the field yourself. This extension allows you to only apply the strategy if the field is null at persistence. This extension has no effect on primitive field types (which can't be null) and the value-strategy will always be applied to such fields.	true | false
relation-discriminator-column	Name of a column to use for discrimination of the relation used by objects stored. This is defined when, for example, a join table is shared by multiple relations and the objects placed in the join table need discriminating for which relation they are for	RELATION_DISCRIM
relation-discriminator-pk	Whether the column added for the discrimination of relations is to be part of the PK when using a join table.	true | false
relation-discriminator-value	Value to use in the relation discriminator column for objects of this fields relation. This is defined when, for example, a join table is shared by multiple relations and the objects placed in the join table need discriminating for which relation they are for.	Fully-qualified class name
select-function	Permits to use a function when fetching contents from the database. A ? (question mark) is mandatory to have and will be replaced by the column name when generating the SQL statement. For example to specify a value of UPPER(?) will convert the field value to upper case on a datastore that supports that UPPER function.
insert-function	Permits to use a function when inserting into the database. A ? (question mark) is optional and will be replaced by the column name when generating the SQL statement. For example to specify a value of TRIM(?) will trim the field value on a datastore that supports that TRIM function.
update-function	Permits to use a function when updating into the database. A ? (question mark) is optional and will be replaced by the column name when generating the SQL statement. For example to specify a value of FUNC(?) will perform "FUNC" on the field value on a datastore that supports that FUNC function.
sequence-table-basis	This defines the basis on which to generate unique identities when using the TablePoidGenerator (used by the "increment" strategy, and sometimes by "native"). You can either define identities unique against the base table name, or against the base class name (in an inheritance tree). Used when the strategy is set to native or increment	class | table
sequence-catalog-name	The catalog used to store sequences for use by poid generators. See Value Generation. Default catalog for the datastore will be used if not specified.
sequence-schema-name	The schema used to store sequences for use by poid generators. See Value Generation. Default schema for the datastore will be used if not specified.
sequence-table-name	The table used to store sequences for use by poid generators. See Value Generation.	SEQUENCE_TABLE
sequence-name-column-name	The column name in the sequence-table used to store the name of the sequence for use by poid generators. See Value Generation.	SEQUENCE_NAME
sequence-nextval-column-name	The column name in the sequence-table used to store the next value in the sequence for use by poid generators. See Value Generation.	NEXT_VAL
key-min-value	The minimum key value for use by poid generators. Keys lower than this will not be generated. See Value Generation.
key-max-value	The maximum key value for use by poid generators. Keys higher than this will not be generated. See Value Generation.
key-start-with	The starting value for use by poid generators. Keys will start from this value when being generated. See Value Generation.
key-increment-by	The increment value for use by poid generators. Keys will be incremented by this value when being generated. See Value Generation.
key-database-cache-size	The database cache size for keys for use by poid generators. The cache of keys will be constrained by this value. See Value Generation.
key-cache-size	The cache size for keys for use by poid generators. The cache of keys will be constrained by this value. See Value Generation.
mapping-class	Specifies the mapping class to be used for mapping this field. This is only used where the user wants to override the default DataNucleus mapping class and provide their own mapping class for this field.	Fully-qualified class name

Metadata for property tag

These are attributes within the <property> tag (jdo/package/class/property). This is used to define the persistence behaviour of the Java Bean properties of the class to which it pertains. This element can be used to change the default behaviour and maybe not persist a property, or to persist something that normally isn't persisted. It is used, in addition, to define more details about how the property is persisted in the datastore.

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the property. The "name" of a property is obtained by taking the getXXX, setXXX method names and using the XXX and making the first letter lowercase.
persistence-modifier	The persistence-modifier specifies how to manage each property in your persistent class. There are three options: persistent, transactional and none. persistent means that your field will be managed and stored in the database on transaction commit. transactional means that your field will be managed but not stored in the database. Transactional fields values will be saved by JDO when you start your transaction and restored when you roll back your transaction. none means that your field will not be managed.	persistent, transactional, none
primary-key	Whether the property is part of any primary key (if using application identity ).	true, false
null-value	How to treat null values of persistent properties during storage.	exception, default, none
default-fetch-group	Whether this property is part of the default fetch group for the class. Defaults to true for non-key fields of primitive types, java.util.Date, java.lang.*, java.math.*, etc.	true , false
embedded	Whether this property should be stored, if possible, as part of the object instead as its own object in the datastore. This defaults to true for primitive types, java.util.Date, java.lang.*, java.math.* etc and false for PersistenceCapable, reference (Object, Interface) and container types.	true, false
serialized	Whether this property should be stored serialised into a single column of the table of the containing object.	true, false
dependent	Whether the property should be used to check for dependent objects, and to delete them when this object is deleted. In other words cascade delete capable.	true, false
mapped-by	The name of the property at the other end of a relationship. Used by 1-1, 1-N, M-N to mark a relation as bidirectional.
value-strategy	The strategy for populating values to this property. Is typically used for generating primary key values. See the definitions under "datastore-identity".	native | sequence | increment | identity | uuid-string | uuid-hex | auid | max | timestamp | timestamp-value | [other values]
sequence	Name of the sequence to use to generate values, when using a strategy of sequence . Please see also the class extension tags for controlling the sequence.
recursion-depth	The depth that will be recursed when this property is self-referencing. Should be used alongside FetchPlan.setMaxFetchDepth() to control the objects fetched.	-1, 1 , 2, ... (integer)
field-type	Used to specify a more restrictive type than the property definition in the class. This might be required in order to map the field to the datastore. To be portable, specify the name of a single type that is itself able to be mapped to the datastore (e.g. a field of type Object can specify field-type="Integer").
indexed	Whether the column(s) for this property should be indexed. This is to be specified when defining index information	true | false | unique
table	Table name to use for any join table overriding the default name provided by DataNucleus. This is used either for 1-N relationships with a join table or for Secondary Tables. See also the property name "datanucleus.identifier.case" in the Persistence Properties Guide.
column	Column name to use for this property (alternative to specifying column sub-elements if only one column).
delete-action	The foreign-key delete action. This is a shortcut to specifying foreign key information. Please refer to the <foreign-key> element for full details.	cascade | restrict | null | default | none

These are attributes within the <extension> tag (jdo/package/class/property/extension).

Attribute	Description	Values
Extension (JDO) Tags
cascade-persist	JDO defines that when an object is persisted then all fields will also be persisted using "persistence-by-reachability". This extension allows you to turn off the persistence of a field relation.	true | false
cascade-update	JDO defines that when an object is updated then all fields containing PersistenceCapable objects will also be updated using "persistence-by-reachability". This extension allows you to turn off the update of a field relation.	true | false
cascade-refresh	When calling PersistenceManager.refresh() only fetch plan fields of the passed object will be refreshed. Setting this to true will refresh the fields of related PC objects in this field	true | false
allows-null	When the field is a collection by default it will not be allowed to have nulls present but you can allow them by setting this DataNucleus extension tag	true | false
insertable	Whether this field should be supplied when inserting into the datastore.	true | false
updateable	Whether this field should be supplied when updating the datastore.	true | false
adapter-column-name	In some situations DataNucleus will add a special datastore column to a join table so that collections can allow the storage of duplicate elements. This extension allows the specification of the column name to be used. This should be specified within the field at the collection end of the relationship. JDO2 doesnt allow a standard place for such a specification and so is an extension tag.	INTEGER_IDX
implementation-classes	Used to define the possible classes implementing this interface/Object field. This is used to limit the possible tables that this is a foreign key to (when this field is specified as an interface/Object in the class). Value should be comma-separated list of fully-qualified class names
key-implementation-classes	Used to define the possible classes implementing this interface/Object key. This is used to limit the possible tables that this is a foreign key to (when this key is specified as an interface/Object). Value should be comma-separated list of fully-qualified class names
value-implementation-classes	Used to define the possible classes implementing this interface/Object value. This is used to limit the possible tables that this is a foreign key to (when this value is specified as an interface/Object). Value should be comma-separated list of fully-qualified class names
strategy-when-notnull	This is to be used in conjunction with the "value-strategy" attribute. Default JDO2 behaviour when you have a "value-strategy" defined for a field is to always create a strategy value for that field regardless of whether you have set the value of the field yourself. This extension allows you to only apply the strategy if the field is null at persistence. This extension has no effect on primitive field types (which can't be null) and the value-strategy will always be applied to such fields.	true | false
relation-discriminator-column	Name of a column to use for discrimination of the relation used by objects stored. This is defined when, for example, a join table is shared by multiple relations and the objects placed in the join table need discriminating for which relation they are for	RELATION_DISCRIM
relation-discriminator-pk	Whether the column added for the discrimination of relations is to be part of the PK when using a join table.	true | false
relation-discriminator-value	Value to use in the relation discriminator column for objects of this fields relation. This is defined when, for example, a join table is shared by multiple relations and the objects placed in the join table need discriminating for which relation they are for.	Fully-qualified class name
select-function	Permits to use a function when fetching contents from the database. A ? (question mark) is mandatory to have and will be replaced by the column name when generating the SQL statement. For example to specify a value of UPPER(?) will convert to upper case the field value on a datastore that supports that UPPER function.
insert-function	Permits to use a function when inserting into the database. A ? (question mark) is optional and will be replaced by the column name when generating the SQL statement. For example to specify a value of TRIM(?) will trim the field value on a datastore that supports that TRIM function.
update-function	Permits to use a function when updating into the database. A ? (question mark) is optional and will be replaced by the column name when generating the SQL statement. For example to specify a value of FUNC(?) will perform FUNC() on the field value on a datastore that supports that FUNC function.
sequence-table-basis	This defines the basis on which to generate unique identities when using the TablePoidGenerator (used by the "increment" strategy, and sometimes by "native"). You can either define identities unique against the base table name, or against the base class name (in an inheritance tree). Used when the strategy is set to native or increment	class | table
sequence-catalog-name	The catalog used to store sequences for use by poid generators. See Value Generation. Default catalog for the datastore will be used if not specified.
sequence-schema-name	The schema used to store sequences for use by poid generators. See Value Generation. Default schema for the datastore will be used if not specified.
sequence-table-name	The table used to store sequences for use by poid generators. See Value Generation.	SEQUENCE_TABLE
sequence-name-column-name	The column name in the sequence-table used to store the name of the sequence for use by poid generators. See Value Generation.	SEQUENCE_NAME
sequence-nextval-column-name	The column name in the sequence-table used to store the next value in the sequence for use by poid generators. See Value Generation.	NEXT_VAL
key-min-value	The minimum key value for use by poid generators. Keys lower than this will not be generated. See Value Generation.
key-max-value	The maximum key value for use by poid generators. Keys higher than this will not be generated. See Value Generation.
key-start-with	The starting value for use by poid generators. Keys will start from this value when being generated. See Value Generation.
key-increment-by	The increment value for use by poid generators. Keys will be incremented by this value when being generated. See Value Generation.
key-database-cache-size	The database cache size for keys for use by poid generators. The cache of keys will be constrained by this value. See Value Generation.
key-cache-size	The cache size for keys for use by poid generators. The cache of keys will be constrained by this value. See Value Generation.
mapping-class	Specifies the mapping class to be used for mapping this field. This is only used where the user wants to override the default DataNucleus mapping class and provide their own mapping class for this field.	Fully-qualified class name

Metadata for fetch-group tag

These are attributes within the <fetch-group> tag (jdo/package/class/fetch-group). This element is used to define fetch groups that are utilised at runtime, and are of particular use with attach/detach. This element can contain fetch-group sub-elements allowing definition of hierarchical groups. It can also contain field elements, defining the fields that are part of this fetch-group.

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the fetch group. Used with the fetch plan of the PersistenceManager.
post-load	Whether to call jdoPostLoad when the fetch group is invoked.	true | false

Metadata for embedded tag

These are attributes within the <embedded> tag (jdo/package/class/embedded). It is used when this field is a PersistenceCapable and is embedded into the same table as the class.

Attribute	Description	Values
Standard (JDO) Tags
owner-field	Name of the field in the embedded PersistenceCapable that is the link back to the owning object (if any).
null-indicator-column	Name of the column to be used for detacting if the embedded object is null.
null-indicator-value	Value of the null-indicator-column that signifies that the embedded object is null.

Metadata for key tag

These are attributes within the <key> tag (jdo/package/class/field/key). This element is used to define details for the persistence of a Map.

Attribute	Description	Values
Standard (JDO) Tags
mapped-by	When the map is formed by a foreign-key, the key can be a field in a value PersistenceCapable class. This attribute defines which field in the value class is used as the key
column	Name of the column (if only one)
delete-action	Action to be performed when the owner object is deleted. This is to be specified when defining foreign key information	cascade | restrict | null | default | none
indexed	Whether the key column should be indexed. This is to be specified when defining index information	true | false | unique
unique	Whether the key column should be unique. This is to be specified when defining unique key information	true | false

Metadata for value tag

These are attributes within the <value> tag (jdo/package/class/field/value). This element is used to define details for the persistence of a Map.

Attribute	Description	Values
mapped-by	When the map is formed by a foreign-key, the value can be a field in a key PersistenceCapable class. This attribute defines which field in the key class is used as the value.
Standard (JDO) Tags
column	Name of the column (if only one)
delete-action	Action to be performed when the owner object is deleted. This is to be specified when defining foreign key information	cascade | restrict | null | default | none
indexed	Whether the value column should be indexed. This is to be specified when defining index information	true | false | unique
unique	Whether the value column should be unique. This is to be specified when defining unique key information	true | false

Metadata for order tag

These are attributes within the <order> tag (jdo/package/class/field/order). This is used to define the column details for the ordering column in a List.

Attribute	Description	Values
Standard (JDO) Tags
mapped-by	When a List is formed by a foreign-key, the ordering can be a field in the element PersistenceCapable class. This attribute defines which field in the element class is used as the ordering. The field must be of type int , Integer , long , Long . DataNucleus will write the index positions to this field (starting at 0 for the first item in the List)
column	Name of the column to use for ordering.

These are attributes within the <extension> tag (jdo/package/class/field/order/extension).

Attribute	Description	Values
Extension (JDO) Tags
list-ordering	Used to make the list be an "ordered list" where it has no index column and instead will order the elements by the specified expression upon retrieval. The ordering expression takes names and ASC/DESC and can be a composite	{valid ordering expression}

Metadata for index tag

These are attributes within the <index> tag (jdo/package/class/field/index). This element is used where a user wishes to add specific indexes to the datastore to provide more efficient access to particular fields.

Attribute	Description	Values
Standard (JDO) Tags
name	Name of the index in the datastore
unique	Whether the index is unique	true | false
column	Name of the column to use (alternative to specifying it as a sub-element).

These are attributes within the <extension> tag (jdo/package/class/field/index/extension).

Attribute	Description	Values
Extension (JDO) Tags
extended-setting	Additional settings to the index. This extension is used to set database proprietary settings.

Metadata for foreign-key tag

These are attributes within the <foreign-key> tag (jdo/package/class/field/foreign-key). This is used where the user wishes to define the behaviour of the foreign keys added due to the relationships in the object model. This is to be read in conjunction with foreign-key guide

Attribute	Description	Values