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Difference between revisions of "EclipseLink/Development/JPA2.0/Extended Map support"
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=== Basic - Basic === | === Basic - Basic === | ||
* Both key and value are a basic | * Both key and value are a basic | ||
| − | * | + | * Target table is same for key and for the favlue |
* CollectionTable contains foreign keys to the source, key and value | * CollectionTable contains foreign keys to the source, key and value | ||
| − | * This | + | * This is BasicMapMapping |
| − | + | * Can also be supported with a BasicCollectionMapping with a MappedKeyMapContainerPolicy containing a DirectToFieldMapping | |
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=== Embeddable - Basic === | === Embeddable - Basic === | ||
* Key is Embeddable, value is Basic | * Key is Embeddable, value is Basic | ||
| − | * | + | * Information about the key and the value are both stored in the target table |
* CollectionTable contains foreign keys to the source, all the fields of the embeddable and the value | * CollectionTable contains foreign keys to the source, all the fields of the embeddable and the value | ||
| − | * | + | * BasicCollectionMapping with MappedKeyMapContainerPolicy containing an AggregateObjectMapping |
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| + | === Entity - Basic === | ||
| + | * Key is Entity, value is Basic | ||
| + | * target table contains foreign keys to the source, foreign keys to the key and the value | ||
| + | * BasicCollectionMapping with MappedKeyMapContainerPolicy containing a OneToOneMapping | ||
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| + | === Basic - Embeddable === | ||
| + | * Key is a basic, value is Embeddable | ||
| + | * target table contains - foreign keys to the source, key and all attributes of Embeddable | ||
| + | * AggregateCollectionMapping with MappedKeyMapContainerPolicy containing a DirectToFieldMapping | ||
=== Embeddable - Embeddable === | === Embeddable - Embeddable === | ||
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* Uses a Collection Table | * Uses a Collection Table | ||
* Collection Table contains a forein key, all the fields of both embeddables (note: if key and value map to the same columns through overrides then the table will only contain one set of information about the embeddable) | * Collection Table contains a forein key, all the fields of both embeddables (note: if key and value map to the same columns through overrides then the table will only contain one set of information about the embeddable) | ||
| − | * | + | * AggregateCollectionMapping with MappedKeyMapContainerPolicy containing an AggregateObjectMapping |
| − | === | + | === Entity - Embeddable === |
| − | * Key is | + | * Key is Entity, value is Embeddable |
| − | * | + | * target table contains foreign keys to the source, foreign keys to the key and all the values of the embedded value |
| − | + | * AggregateCollectionMapping with MappedKeyMapContainerPolicy containing a OneToOneMapping | |
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| − | === Entity | + | === x - Entity === |
| − | * | + | * The majority of the cases occur when the target is an Entity |
| − | * | + | * The mappings: OneToMany, UnidirectionalOneToMany and ManyToMany are potentially used |
| − | + | ||
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| + | ==== Basic/Embeddable - Entity ==== | ||
| + | * Key is a basic or embeddable, and value is an entity | ||
| + | * Several possible use cases | ||
| + | ** Key is a mapped value in target object | ||
| + | *** Covered by our current MapKey support | ||
| + | *** OneToMany, UnidirectionalOneToMany and ManyToMany | ||
| + | ** Key is stored in target table, but not mapped in target object | ||
| + | *** target table contains values needed to build the target and values needed to build the key | ||
| + | *** OneToManyMapping or UnidirectionalOneToManyMapping with MappedKeyMapContainerPolicy containing a DirectToFieldMapping or AggregateObjectMapping | ||
| + | ** Key is stored in collection table | ||
| + | *** collection table contains foreign keys to the source, foreign keys to the value, and all fields need to build the key | ||
| + | *** ManyToManyMapping with MappedKeyMapContainerPolicy containing a DirectToFieldMapping or AggregateObjectMapping | ||
| − | === Entity - | + | ==== Entity - Entity ==== |
| − | * Key is Entity, | + | * Key is an Entity, Value is an Entity |
| − | * | + | * Several possible use cases |
| − | * | + | ** Key is a mapped value in target object |
| − | + | *** Covered by our current MapKey support | |
| − | + | *** OneToMany, UnidirectionalOneToMany and ManyToMany | |
| − | + | ** Key is referenced from target table but not mapped in target object | |
| − | * Key is | + | *** target table contains values need to build the target, and foreign keys to the key |
| − | * | + | *** OneToManyMapping or UnidirectionalOneToManyMapping with MappedKeyMapContainerPolicy containing a OneToOneMapping |
| − | ** | + | ** Key is referenced from the collection table |
| − | ** | + | *** collection table contains foreign keys to the source, foreign keys to the value, and foreign keys to the key |
| − | *** | + | *** ManyToManyMapping with MappedKeyMapContainerPolicy containing a OneToOneMapping |
| − | *** | + | |
| − | ** | + | |
| − | *** | + | |
| − | *** | + | |
| − | + | ||
== Design == | == Design == | ||
Revision as of 15:34, 15 December 2008
Contents
JPA 2.0 Map Support
Issue summary
- Map support as defined in JPA 2.0 will require new mapping functionality for EclipseLink. The specification will allow any JPA 1.0 relationship mapping to be stored in a map with key being a primitive, an Embeddable or an Entity. For this support no user defined mapping or property exists on the target of the relationship as is the case in our current support. An additional complication is that the location of the Key fields exist on the relation table if one exists.
The Solution in General
- Map behavior in EclipseLink is handled through ContainerPolicy. These mappings will be no different. a new subclass of MapContainerPolicy (MappedKeyMapContainerPolicy) will be added that is capable of reading and writing map keys that are stored in a database table, but not in the owning Entity, itself.
Use Cases
Both keys and values can be either of the following types: Basic, Embeddable, Entity. This results in the following types of maps.
Basic - Basic
- Both key and value are a basic
- Target table is same for key and for the favlue
- CollectionTable contains foreign keys to the source, key and value
- This is BasicMapMapping
- Can also be supported with a BasicCollectionMapping with a MappedKeyMapContainerPolicy containing a DirectToFieldMapping
Embeddable - Basic
- Key is Embeddable, value is Basic
- Information about the key and the value are both stored in the target table
- CollectionTable contains foreign keys to the source, all the fields of the embeddable and the value
- BasicCollectionMapping with MappedKeyMapContainerPolicy containing an AggregateObjectMapping
Entity - Basic
- Key is Entity, value is Basic
- target table contains foreign keys to the source, foreign keys to the key and the value
- BasicCollectionMapping with MappedKeyMapContainerPolicy containing a OneToOneMapping
Basic - Embeddable
- Key is a basic, value is Embeddable
- target table contains - foreign keys to the source, key and all attributes of Embeddable
- AggregateCollectionMapping with MappedKeyMapContainerPolicy containing a DirectToFieldMapping
Embeddable - Embeddable
- Key is Embeddable, value is Embeddable
- Uses a Collection Table
- Collection Table contains a forein key, all the fields of both embeddables (note: if key and value map to the same columns through overrides then the table will only contain one set of information about the embeddable)
- AggregateCollectionMapping with MappedKeyMapContainerPolicy containing an AggregateObjectMapping
Entity - Embeddable
- Key is Entity, value is Embeddable
- target table contains foreign keys to the source, foreign keys to the key and all the values of the embedded value
- AggregateCollectionMapping with MappedKeyMapContainerPolicy containing a OneToOneMapping
x - Entity
- The majority of the cases occur when the target is an Entity
- The mappings: OneToMany, UnidirectionalOneToMany and ManyToMany are potentially used
Basic/Embeddable - Entity
- Key is a basic or embeddable, and value is an entity
- Several possible use cases
- Key is a mapped value in target object
- Covered by our current MapKey support
- OneToMany, UnidirectionalOneToMany and ManyToMany
- Key is stored in target table, but not mapped in target object
- target table contains values needed to build the target and values needed to build the key
- OneToManyMapping or UnidirectionalOneToManyMapping with MappedKeyMapContainerPolicy containing a DirectToFieldMapping or AggregateObjectMapping
- Key is stored in collection table
- collection table contains foreign keys to the source, foreign keys to the value, and all fields need to build the key
- ManyToManyMapping with MappedKeyMapContainerPolicy containing a DirectToFieldMapping or AggregateObjectMapping
- Key is a mapped value in target object
Entity - Entity
- Key is an Entity, Value is an Entity
- Several possible use cases
- Key is a mapped value in target object
- Covered by our current MapKey support
- OneToMany, UnidirectionalOneToMany and ManyToMany
- Key is referenced from target table but not mapped in target object
- target table contains values need to build the target, and foreign keys to the key
- OneToManyMapping or UnidirectionalOneToManyMapping with MappedKeyMapContainerPolicy containing a OneToOneMapping
- Key is referenced from the collection table
- collection table contains foreign keys to the source, foreign keys to the value, and foreign keys to the key
- ManyToManyMapping with MappedKeyMapContainerPolicy containing a OneToOneMapping
- Key is a mapped value in target object
Design
Archived Initial Design
The following contains information about the initial design proposal. It has now been modified.
The Solution in General
- The general approach to implementing this functionality will be to produce Map mappings that encapsulate two EclipseLink mappings. A generated mapping that represents the Key attribute and a user defined mapping that represents the value of the map. It is expected that two Map Mappings will be needed. A Mapping where the Key mapping columns are found in the target table and another where the Key mapping columns are found in the relation table (CollectionTableMapMapping).
The Details
- Target Table Map Mapping
- Enhancement Request
- This support will cover the case where the Map key columns exist in the target table
- EclipseLink Mappings Involved
- - AggregateCollectionMapping
- - Bi-directional OneToMany
- - New Uni-directional OneToMany mapping
- EclipseLink Mappings Involved
- JPA Mappings
- - Bi-directional OneToMany mapping
- - Uni-directional OneToMany with @JoinColum
- - ElementCollection<*, Primitive> mapping
- - ElementCollection<*, Embeddable> mapping
- JPA Mappings
- Join Table Map Mapping (or CollectionTableMapMapping)
- Enhancement Request
- This support will cover the case where the Map key columns exist in the Join table
- EclipseLink Mappings Involved
- - ManyToMany mapping
- EclipseLink Mappings Involved
- JPA Mappings
- - default Uni-directional OneToMany with @JoinColum
- - ManyToMany mapping
- - Note: The specification disallows both sides of a mapping using a Map collection but there is no technical reason to do this as one side will be read-only anyway.
- JPA Mappings