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{{EclipseLink_UserGuide
 
|info=y
 
|toc=n
 
|eclipselink=y
 
|eclipselinktype=JPA}}
 
=Overriding and Merging XML=
 
You can use EclipseLink’s native metadata xml file, [[EclipseLink/UserGuide/JPA/Basic JPA Development/Configuration/JPA/eclipselink-orm.xml|<tt>eclipselink-orm.xml</tt>]], to override mappings defined in JPA’s configuration file <tt>[[EclipseLink/UserGuide/JPA/Basic JPA Development/Configuration/JPA/orm.xml|orm.xml]]</tt> and provide EclipseLink with extended ORM features.
 
{{EclipseLink_Spec
 
|link=http://jcp.org/en/jsr/detail?id=220
 
|section=Section 12.2 "XML Overriding Rules"
 
}}
 
  
When both <tt>orm.xml</tt> and <tt>eclipselink-orm.xml</tt> are specified in a project, the contents of <tt>eclipselink-orm.xml</tt> override <tt>orm.xml</tt> and any other JPA mapping file specified in the persistence unit. If there are overlapping specifications in multiple ORM files, the files are merged if they are no conflicting entities.
 
{{EclipseLink_Note
 
|note=The order of files defined in <tt>persistence.xml</tt> does not define the order of their processing. The files are processed, merged and overidden as required. For more information, see [[#Overriding and Merging Examples|Overriding and Merging Examples]].}}
 
  
The EclipseLink-ORM.XML file can be referenced for inclusion in a persistence unit’s metadata through any of the following files or methods:
 
{|{{BMTableStyle}}
 
|-{{BMTHStyle}}
 
! File/Method
 
! Description
 
|-
 
| <tt>META-INF/eclipselink-orm.xml</tt>
 
| Provides mapping overriding capabilities.
 
|-
 
| <tt>META-INF/orm.xml</tt>
 
| The default ORM file provided with JPA.
 
|- 
 
| Referenced as persistence unit mapping file in <tt>persistence.xml</tt>
 
| Does not provide mapping overriding capability, but can be used for merging mapping files.
 
|}
 
  
==Overriding and Merging Examples==
+
'''[[Image:Elug_draft_icon.png|Warning]] See "Overriding and Merging Mapping Information" in the [http://www.eclipse.org/eclipselink/documentation/ EclipseLink Concepts Guide]'''
 
+
'''''Example 1'''''
+
* <tt>META-INF/orm.xml</tt> - defines Entity A with the mappings b and c.
+
* <tt>META-INF/eclipselink-orm.xml</tt> - defines Entity A with the mappings for c and d.
+
* Result - Entity A will contain the mapping b (from <tt>orm.xml</tt>), mapping c and d (from <tt>eclipselink-orm.xml</tt>)
+
 
+
'''''Example 2'''''
+
* <tt>META-INF/orm.xml</tt> - defines Entity A with the mappings b and c
+
* <tt>META-INF/some-other-mapping-file.xml</tt> - defines Entity B with mappings a and b
+
* <tt>META-INF/eclipselink-orm.xml</tt> - defines Entity A with the mappings for c and d and Entity B with the mapping b and c
+
* Result
+
** Entity A will contain the mapping b (from <tt>orm.xml</tt>), mapping c and d (from <tt>eclipselink-orm.xml</tt>)
+
** Entity B will contain the mapping a (from <tt>some-other-mapping-file</tt>), mappings b and c (from <tt>eclipselink-orm.xml</tt>)
+
 
+
'''''Example 3'''''
+
* <tt>META-INF/orm.xml</tt> - defines Entity A with the mappings b and c.
+
* <tt>META-INF/eclipselink-orm.xml</tt> - defines Entity A with the mappings c and d.
+
* <tt>META-INF/some-other-mapping-file.xml</tt> - defines Entity A with the mapping x.
+
* Result - Entity A will contain the mapping b (from <tt>orm.xml</tt>), mapping c and d (from <tt>eclipselink-orm.xml</tt>) and mapping x (from some-other-mapping-file)
+
+
'''''Example 4'''''
+
* <tt>META-INF/orm.xml</tt> - defines Entity A with the mappings b and c.
+
* <tt>META-INF/extensions/eclipselink-orm.xml</tt> - defines defines Entity A with the mappings c and d. <br> '''Note:''' This file is added through a <mapping-file> tag in the <tt>persistence.xml</tt>
+
* Result -  Exception generated for conficting specifications for mapping c.
+
 
+
'''''Example 5'''''
+
* <tt>META-INF/orm.xml</tt> - defines Entity A with the mappings b and c.
+
* <tt>META-INF/jpa-mapping-file.xml</tt> - defines Entity A with the mappings a and d.
+
* <tt>META-INF/extensions/eclipse-mapping-file.xml</tt> - defines defines Entity A with the mappings c and d.
+
* Result - Exception generated for conficting specifications for mapping c or d (which ever is processed first).
+
 
+
==Overriding and Merging Rules==
+
The following sections outlines elements defined in <tt>orm.xml</tt> and their specific overriding in greater detail.
+
 
+
===Persistence Unit Metadata===
+
In EclipseLink-ORM.XML, a persistence-unit-metadata specification merges or overrides the values of existing persistence-unit-metadata specification.
+
 
+
{|{{BMTableStyle}}
+
|-{{BMTHStyle}}
+
! entity-mappings/persistence-unit-metadata
+
! Rule
+
! Description
+
|-
+
| xml-mapping-metadata-complete
+
| Full override
+
| If specified, the complete set of mapping metadata for the persistence unit is contained in the XML mapping files for the persistence unit.
+
|-
+
| persistence-unit-defaults/schema
+
| Full override
+
| If a schema setting exists, then the EclipseLink-ORM.XML's schema setting overrides the existing setting, or creates a new schema setting.
+
|-
+
| persistence-unit-defaults/catalog
+
| Full override
+
| If a catalog setting exists, then the EclipseLink-ORM.XML's catalog setting overrides the existing setting, or creates a new catalog setting
+
|-
+
| persistence-unit-defaults/access
+
| Full override
+
| If an access setting exists, then the EclipseLink-ORM.XML's access setting overrides the existing setting, or creates a new access setting.
+
|-
+
| entity-mappings/persistence-unit-metadata/persistence-unit-defaults/cascade-persist
+
| Full override
+
| If a cascade-persist setting exists, then the EclipseLink-ORM.XML's cascade-persist setting overrides the existing setting, or creates a new cascade-persist setting.
+
|-
+
| entity-mappings/persistence-unit-metadata/persistence-unit-defaults/entity-listeners
+
| Merge
+
| If an entity-listeners exists, then the EclipseLink-ORM.XML's entity-listeners will be merged with the list of all entity-listeners from the persistence unit.
+
|}
+
 
+
===Entity Mappings===
+
Entities, embeddables and mapped superclasses are defined within entity-mappings. EclipseLink-ORM.XML's entities, embeddables and mapped superclasses are added to the persistence unit. The following table describes the top-level elements of the entity-mappings sections:
+
 
+
{|{{BMTableStyle}}
+
|-{{BMTHStyle}}
+
! entity-mappings/
+
! Rule
+
! Description
+
|-
+
| package
+
| None
+
| The package element specifies the package of the classes listed within the subelements and attributes of the same mapping file only. It is only applicable to those entities that are fully defined within the EclipseLink-ORM.XML file, else its usage remains local and is same as described in the JPA specification.
+
|-
+
| catalog
+
| None
+
| The catalog element applies only to the subelements and attributes listed within the EclipseLink-ORM.XML file that are not an extension to another mapping file. Otherwise, the use of the catalog element within the EclipseLink-ORM.XML file remains local and is same as described in the JPA specification.
+
|-
+
| schema
+
| None
+
| The schema element applies only to the subelements and attributes listed within the EclipseLink-ORM.XML file that are not an extension to another mapping file. Otherwise, the use of the schema element within the EclipseLink-ORM.XML file remains local and is same as described in the JPA specification.
+
|-
+
| access
+
| None
+
| The access element applies only to the subelements and attributes listed within the EclipseLink-ORM.XML file that are not an extension to another mapping file. Otherwise, the use of the access element within the EclipseLink-ORM.XML file remains local and is same as described in the JPA specification.
+
|-
+
| sequence-generator
+
| Full override
+
| A sequence-generator is unique by name. The sequence-generator defined in the EclipseLink-ORM.XML will override a sequence-generator of the same name defined in another mapping file. Outside of the overriding case, an exception is thrown if two or more sequence-generators with the same name are defined in one or across multiple mapping files.
+
|-
+
| table-generator
+
| Full override
+
| A table-generator is unique by name. The table-generator defined in the EclipseLink-ORM.XML will override a table-generator of the same name defined in another mapping file. Outside of the overriding case, an exception is thrown if two or more table-generators with the same name are defined in one or across multiple mapping files.
+
|-
+
| named-query
+
| Full override
+
| A named-query is unique by name. The named-query defined in the EclipseLink-ORM.XML will override a named-query of the same name defined in other mapping files. Outside of the overriding case, an exception is thrown if two or more named-querys with the same name are defined in one or across multiple mapping file.
+
|-
+
| named-native-query
+
| Full override
+
| A named-native-query is unique by name. The named-native-query defined in the EclipseLink-ORM.XML will override a named-native-query of the same name defined in other mapping files. Outside of the overriding case, an exception is thrown if two or more named-native-querys with the same name are defined in one or across multiple mapping files.
+
|-
+
| sql-result-set-mapping
+
| Full override
+
| A sql-result-set-mapping is unique by name. The sql-result-set-mapping defined in the EclipseLink-ORM.XML will override a sql-result-set-mapping of the same name defined in other mapping files. Outside of the overriding case, an exception is thrown if two or more sql-result-set-mapping entities with the same name are defined in one or across multiple mapping files.
+
|}
+
 
+
===Mapped Superclass===
+
A mapped-superclass can be defined completely, or with specific elements to provide extensions to a mapped-superclass from another mapping file.  The following table lists individual override and merging rules:
+
 
+
{|{{BMTableStyle}}
+
|-{{BMTHStyle}}
+
! entity-mappings/mapped-superclass
+
! Rule
+
! Description
+
|-
+
| id-class
+
| Full override
+
| If an id-class setting exists, then the EclipseLink-ORM.XML's id-class setting overrides the existing setting, or creates a new id-class setting.
+
|-
+
| exclude-default-listeners
+
| Full override
+
| If an exclude-default-listeners setting exists, then the EclipseLink-ORM.XML's exclude-default-listeners setting will be applied.  If the exclude-default-listeners setting is not specified, it will not override an existing setting, that is essentially turning it off.
+
|-
+
| exclude-superclass-listeners
+
| Full override
+
| If an exclude-superclass-listeners setting exists, then the EclipseLink-ORM.XML's exclude-superclass-listeners setting will be applied.  If exclude-superclass-listeners setting is not specified, it will not override an existing setting, that is essentially turning it off.
+
|-
+
| entity-listeners
+
| Merge and full override
+
| If an entity-listeners setting exists, then the EclipseLink-ORM.XML's entity-listeners setting will override and merge with an existing setting, or creates a new entity-listeners setting all together. <br>{{EclipseLink_Note|note=An entity listener override must be complete. All lifecycle methods of that listener must be specified and no merging of individual lifecycle methods of an entity listener is allowed.  The class name of the listener is the key to identify the override.}}
+
|-
+
| pre-persist
+
| Full override
+
| If a pre-persist setting exists, then the EclipseLink-ORM.XML's pre-persist setting overrides the existing setting, or creates a new pre-persist setting.
+
|-
+
| post-persist
+
| Full override
+
| If a post-persist setting exists, then the EclipseLink-ORM.XML's post-persist setting overrides the existing setting, or creates a new post-persist setting.
+
|-
+
| pre-remove
+
| Full override
+
| If a pre-remove setting exists, then the EclipseLink-ORM.XML's pre-remove setting overrides the existing setting, or creates a new pre-remove setting. 
+
|-
+
| post-remove
+
| Full override
+
| If a post-remove setting exists, then the EclipseLink-ORM.XML's post-remove setting overrides the existing setting, or creates a new post-remove setting. 
+
|-
+
| pre-update
+
| Full override
+
| If a pre-update setting exists, then the EclipseLink-ORM.XML's pre-update setting overrides the existing setting, or creates a new pre-update setting.
+
|-
+
| post-update
+
| Full override
+
| If a post-update setting exists, then the EclipseLink-ORM.XML's post-update setting overrides the existing setting, or creates a new post-update setting.
+
|-
+
| post-load
+
| Full override
+
| If a post-load setting exists, then the EclipseLink-ORM.XML's post-load setting overrides the existing setting, or creates a new post-load setting. 
+
|-
+
| attributes
+
| Merge and mapping level override
+
| If the attribute settings (id, embedded-id, basic, version, many-to-one, one-to-many, one-to-one, many-to-many, embedded, transient) exist at the mapping level, then the EclipseLink-ORM.XML's attributes merges or overrides the existing settings, else creates new attributes. 
+
|-
+
| class
+
| None
+
|
+
|-
+
| access
+
| Full override
+
| If an access setting exists, then the EclipseLink-ORM.XML's access setting overrides the existing setting, or creates a new access setting. It also overrides the default class setting.
+
|-
+
| metadata-complete
+
| Full override
+
| If a metadata-complete setting exists, then the EclipseLink-ORM.XML's metadata-complete setting will be applied.  If metadata-complete setting is not specified, it will not override an existing setting, that is essentially turning it off.
+
|}
+
 
+
===Entity override and merging rules===
+
An entity can be defined completely, or with specific elements to provide extensions to an entity from another mapping file. The following table lists individual override and merging rules: 
+
 
+
{|{{BMTableStyle}}
+
|-{{BMTHStyle}}
+
! entity-mappings/entity
+
! Rule
+
! Comments
+
|-
+
| table
+
| Full override
+
| The table definition overrides any other table setting (with the same name) for this entity. There is no merging of individual table values.
+
|-
+
| secondary-table
+
| Full override
+
| The secondary-table definition overrides another secondary-table setting (with the same name) for this entity. There is no merging of individual secondary-table(s) values. 
+
|-
+
| primary-key-join-column
+
| Full override
+
| The primary-key-join-column(s) definition overrides any other primary-key-join-column(s) setting for this entity. There is no merging of the primary-key-join-column(s). The specification is assumed to be complete and these primary-key-join-columns are the source of truth.
+
|-
+
| id-class
+
| Full override
+
| If an id-class setting exists, then the EclipseLink-ORM.XML's id-class setting overrides the existing setting, or creates a new id-class setting.
+
|-
+
| inheritance
+
| Full override
+
| If an inheritance setting exists, then the EclipseLink-ORM.XML's inheritance setting overrides the existing setting, or creates a new inheritance setting.
+
|-
+
| discriminator-value
+
| Full override
+
| If a discriminator-value setting exists, then the EclipseLink-ORM.XML's discriminator-value setting overrides the existing setting, or creates a new discriminator-value setting.
+
|-
+
| discriminator-column
+
| Full override
+
| If a discriminator-column setting exists, then the EclipseLink-ORM.XML's discriminator-column setting overrides the existing setting, or creates a new discriminator-column setting.
+
|-
+
| sequence-generator
+
| Full override
+
| A sequence-generator is unique by name. The sequence-generator defined in EclipseLink-ORM.XML overrides sequence-generator of the same name defined in other mapping files. Outside of the overriding case, an exception is thrown if two or more sequence-generators with the same name are defined in one or across multiple mapping files.
+
|-
+
| table-generator
+
| Full override
+
| A table-generator is unique by name. The table-generator defined in EclipseLink-ORM.XML overrides table-generator of the same name defined in other mapping files. Outside of the overriding case, an exception is thrown if two or more table-generators with the same name are defined in one or across multiple mapping files.
+
|-
+
| named-query
+
| Merge and full override
+
| A named-query is unique by name. The named-query defined in EclipseLink-ORM.XML overrides named-query of the same name defined in other mapping files. Outside of the overriding case, an exception is thrown if two or more named-query elements with the same name are defined in one or across multiple mapping files.
+
|-
+
| named-native-query
+
| Merge and full override
+
| A named-native-query is unique by name. The named-native-query defined in EclipseLink-ORM.XML overrides named-native-query of the same name defined in other mapping files. Outside of the overriding case, an exception is thrown if two or more named-native-query elements with the same name are defined in one or across multiple mapping files.
+
|-
+
| sql-result-set-mapping
+
| Merge and full override
+
| A sql-result-set-mapping is unique by name. The sql-result-set-mapping defined in EclipseLink-ORM.XML overrides sql-result-set-mapping of the same name defined in other mapping files. Outside of the overriding case, an exception is thrown if two or more sql-result-set-mapping elements with the same name are defined in one or across multiple mapping files.
+
|-
+
| exclude-default-listeners
+
| Full override
+
| If an exclude-default-listeners setting exists, then the EclipseLink-ORM.XML's exclude-default-listeners setting will be applied. If an exclude-default-listeners setting is not specified, it will not override an existing setting, that is essentially turning it off.
+
|-
+
| exclude-superclass-listeners
+
| Full override
+
| If an exclude-superclass-listeners setting exists, then the EclipseLink-ORM.XML's exclude-superclass-listeners setting will be applied. If an exclude-superclass-listeners setting is not specified, it will not override an existing setting, that is essentially turning it off.
+
|-
+
| entity-listeners
+
| Full override
+
| If an entity-listeners setting exists, then the EclipseLink-ORM.XML's entity-listeners setting will override and merge with an existing setting, or creates a new entity-listeners setting all together. <br> {{EclipseLink_Note|note=An entity listener override must be complete. All lifecycle methods of that listener must be specified and no merging of individual lifecycle methods of an entity listener is allowed.  The class name of the listener is the key to identify the override.}}
+
|-
+
| pre-persist
+
| Full override
+
| If a pre-persist setting exists, then the EclipseLink-ORM.XML's pre-persist setting overrides the existing setting, or creates a new pre-persist setting.
+
|-
+
| post-persist
+
| Full override
+
| If a post-persist setting exists, then the EclipseLink-ORM.XML's post-persist setting overrides the existing setting, or creates a new post-persist setting.
+
|-
+
| pre-remove
+
| Full override
+
| If a pre-remove setting exists, then the EclipseLink-ORM.XML's pre-remove setting overrides the existing setting, or creates a new pre-remove setting. 
+
|-
+
| post-remove
+
| Full override
+
| If a post-remove setting exists, then the EclipseLink-ORM.XML's post-remove setting overrides the existing setting, or creates a new post-remove setting.
+
|-
+
| pre-update
+
| Full override
+
| If a pre-update setting exists, then the EclipseLink-ORM.XML's pre-update setting overrides the existing setting, or creates a new pre-update setting.
+
|-
+
| post-update
+
| Full override
+
| If a post-update setting exists, then the EclipseLink-ORM.XML's post-update setting overrides the existing setting, or creates a new post-update setting.
+
|-
+
| post-load
+
| Full override
+
| If a post-load setting exists, then the EclipseLink-ORM.XML's post-load setting overrides the existing setting, or creates a new post-load setting.
+
|-
+
| attributes
+
| Merge and mapping level override
+
| If the attribute settings (id, embedded-id, basic, version, many-to-one, one-to-many, one-to-one, many-to-many, embedded, transient) exist at the mapping level, then the EclipseLink-ORM.XML's attributes merges or overrides the existing settings, else creates new attributes.
+
|-
+
| association-override
+
| Merge and full override
+
| If an association-override setting exists, then the EclipseLink-ORM.XML's association-override setting overrides the existing setting, or creates a new association-override setting.
+
|-
+
| name
+
| Full override
+
| If a name setting exists, then the EclipseLink-ORM.XML's name setting overrides the existing setting, or creates a new name setting.
+
|-
+
| class
+
| None
+
|
+
|-
+
| access
+
| Full override
+
| If an access setting exists, then the EclipseLink-ORM.XML's access setting overrides the existing setting, or creates a new access setting. It also overrides the default class setting.
+
|-
+
| metadata-complete
+
| Full override
+
| If a metadata-complete setting exists, then the EclipseLink-ORM.XML's metadata-complete setting will be applied. If a metadata-complete setting is not specified, it will not override an existing setting, that is essentially turning it off.
+
|}
+
 
+
===Embeddable===
+
An embeddable can be defined wholely or may be defined so as to provide extensions to an embeddeable from another mapping file. Therefore, we will allow the merging of that classes metadata. The individual override rules for that metadata is tabled below.
+
 
+
{|{{BMTableStyle}}
+
|-{{BMTHStyle}}
+
! entity-mappings/embeddable
+
! Rule
+
! Description
+
|-
+
| attributes
+
| Override and merge
+
| If the attribute settings (id, embedded-id, basic, version, many-to-one, one-to-many, one-to-one, many-to-many, embedded, transient) exist at the mapping level, then the EclipseLink-ORM.XML's attributes merges or overrides the existing settings, or creates new attributes.   
+
|-
+
| class
+
| None
+
|
+
|-
+
| access
+
| Full override
+
| If an access setting exists, then the EclipseLink-ORM.XML's access setting overrides the existing setting, or creates a new access setting. It also overrides the default class setting.
+
|-
+
| metadata-complete
+
| Full override
+
| If a metadata-complete setting exists, then the EclipseLink-ORM.XML's metadata-complete setting will be applied. If a metadata-complete setting is not specified, it will not override an existing setting, that is essentially turning it off. 
+
|}
+
 
+
 
+
 
+
{{EclipseLink_JPA
+
|previous=[[EclipseLink/UserGuide/JPA/Basic JPA Development/Configuration/JPA/eclipselink-orm.xml|eclipselink-orm.xml]]
+
|next=[[EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping|Mapping]]
+
|up=[[EclipseLink/UserGuide/JPA/Basic JPA Development/Configuration|Configuration]]
+
|version=2.2.0 DRAFT}}
+

Latest revision as of 11:51, 25 January 2013


Warning See "Overriding and Merging Mapping Information" in the EclipseLink Concepts Guide